Vomiting and Diarrhea in Dogs and Cats: An Expert Guide

Pets commonly suffer from upset digestive systems. But sometimes vomiting and diarrhea in dogs and cats can indicate a serious illness.

Cat looking sick
Vomiting and diarrhea are no fun for anyone. Photo: Samuel Cockman

Cats and dogs commonly suffer from upset digestive systems causing vomiting or diarrhea, or both.

In many cases, the cause of the digestive upset is minor.

However, vomiting and diarrhea can be symptoms of a serious illness.

In this 10-part expert guide to vomiting and diarrhea in dogs and cats, we’ll discuss:

  • Part 1: The Workings of Your Pet’s Digestive System
  • Part 2: Vomiting in Dogs and Cats
  • Part 3: Uh-Oh! Why Is My Cat Throwing Up?
  • Part 4: Uh-Oh! Why Is My Dog Throwing Up?
  • Part 5: Diarrhea in Dogs and Cats
  • Part 6: Recognizing the Warning Signs of Dog Diarrhea
  • Part 7: Blood in the Diarrhea — And What It Means
  • Part 8: How Cobalamin Injections May Help With Diarrhea
  • Part 9: Long-Term Diarrhea in Dogs and Cats
  • Part 10: Common Infections That Can Cause Diarrhea in Puppies

Part 1: The Workings of Your Pet’s Digestive System

To better understand the causes of a cat or dog’s vomiting or diarrhea, it’s useful to have a general idea of your pet’s digestive system and how it works.

The digestive system has the important job of keeping your dog or cat hydrated by bringing water into the body and supplying your pet with nutrients from food.


The digestion process begins when your dog or cat chews food.

Saliva mixes with the food, and an enzyme in the saliva begins to break down the starches in what your pet has eaten.

Saliva also lubricates the chewed food, making it easier to pass through the digestive system.


The chewed food then begins to travel to the stomach via the esophagus. A process called peristalsis causes the muscles of the esophagus to contract in waves that push the chewed food down the length of the esophagus and into the stomach.


Once in the stomach, the chewed food has its proteins broken down by a secretion from the lining of the stomach called pepsin.

Hydrochloric acid is also produced in the stomach, and the acid further breaks down the food for easier digestion.

The food remains in the stomach for one to two hours, and muscular valves on either end of the stomach keep the food from escaping while it is being digested. Muscles in the stomach keep the food moving around among the acid and pepsin to further the process, and then the food passes into the small intestine.

Small Intestine

A long, muscular tube that loops around within the abdomen is the small intestine, and it is made up of three separate sections.

As the food passes through each of these sections — the duodenum, jejunum and ileum — the gallbladder releases bile and the pancreas releases digestive enzymes. Bile reduces lumps of fat into smaller pieces, and the digestive enzymes break down the fat even further.

The digestive enzymes also break down sugars, starches and proteins. All the nutrients released from the digestive process are absorbed into the body through the small intestine’s lining, and the leftover waste passes through to the large intestine.

Large Intestine

The large intestine, also known as the colon, is a large, muscular tube that connects the small intestine and the anus.

In a process of peristalsis, similar to that of passing food through the esophagus, the muscles of the large intestine contract in waves to push the waste through the colon, where the excess moisture is absorbed.

The feces, in solid form, is expelled from the body when the rectal valve muscles relax.

Got all that?

Now let’s talk specifically about vomiting.

Part 2: Vomiting in Dogs and Cats

Causes of Vomiting

Vomiting in pets is typically caused by an irritant that affects either the stomach or the duodenum, which is the first section of the small intestine.

In order to rid the body of the irritant, the process of peristalsis occurs in reverse, so that the irritant works its way back up the esophagus where it is vomited out.

Irritation is most often caused by a cat or dog eating something that is not digestible, such as a bone, a stick or synthetic material, such as plastic.

As Dr. John Harper, DVM, notes, “Young cats and dogs often chew on yarn, string, sticks, rubber and plastic, and other objects that can’t be digested, causing irritation and vomiting.”

Some common causes of vomiting in pets:

  1. Human Foods: Human foods, particularly those that are greasy, can also cause irritation. In simple cases, the pet throws up and health returns to normal within hours. Some irritants may cause vomiting to occur periodically over a day or two before ceasing.
  2. Foreign Object: In some cases, however, a bone, stick or other foreign object may get stuck in the digestive tract, which causes an obstruction. As the body tries to expel the object, the obstruction blocks its path, which further irritates the digestive tract. This can result in persistent vomiting; severe cases can cause projectile vomiting.
  3. Viral or Bacterial Infection: Other common causes of vomiting include infections as a result of a virus or, less commonly, bacteria. Like humans, cats and dogs can get viral or bacterial infections that require medication.
  4. Parasites: Another common cause of vomiting, which affects young pets in particular, is parasites. Parasites, such as roundworms or hookworms, can cause vomiting as the body tries to expel the worms.
  5. Serious Illness: Vomiting is also a symptom of some serious illnesses, such as cancer, liver disease or kidney disease. Cancer, particularly in older pets, can spread to the digestive system, which may cause irritation or obstructions in the digestive tract. A disease of the liver or kidneys causes toxins to build up in the body that causes irritation of the digestive system leading to vomiting.

In the following video, you’ll learn much more about reasons cats throw up:

YouTube player

What to Look For in Vomit:

An examination of the vomit can provide clues as to the cause.

  • Red blood in your pet’s vomit indicates bleeding of the digestive tract relatively close to the esophagus.
  • Darker blood that has the appearance of coffee grounds indicates blood farther down the digestive tract.
  • Vomit tinged with yellow bile may indicate an irritation in the first section of the small intestine; it can also indicate that the animal’s stomach is empty.
  • White substances, particularly those with a spaghetti-like appearance, indicate parasites.

Next, we’ll take a much closer look at this condition — first in cats specifically, and then in dogs.

Vomiting in a cat may be either directly related to the gut or a secondary symptom of another issue. Photo: kiandthemags

Part 3: Uh-Oh! Why Is My Cat Throwing Up?

Is your cat a “happy vomiter,” or is it something more serious?

Some cats are “happy vomiters,” meaning they’re just doing what cats do and there’s nothing pathological about it.

But vomiting can be a sign of significant illness, so how do you recognize when a problem is minor or quite major?

Is My Cat Vomiting?

It can be tricky to spot the difference between vomiting, retching and regurgitation.

But knowing the difference helps your vet target the most appropriate tests.


Vomiting is when partially digested food is ejected from the stomach. Signs include:

  • Salivation and drooling
  • Lip licking
  • Restlessness
  • Abdominal heaving
  • Vomited bile or a large volume of partially digested food


This is food that doesn’t get as far as the stomach and sits for a while in the gullet. Signs include:

  • Little effort is involved — sometimes the cat just lowers his head
  • A sausage-shaped offering
  • No signs such as restlessness, lip licking or drooling


Also known as “dry heaving,” this involves reverse stomach contractions. Signs include:

  • Little abdominal effort
  • No excess salivation
  • Only a small volume of vomit is produced

What Causes Vomiting in a Cat?

There are many reasons cats vomit, but for starters, it’s helpful to know if the problem is “primary” (directly related to the gut) or “secondary” (vomiting is a symptom of a problem elsewhere in the body).

Examples of primary vomiting include:

  • Infection: This could be due to causes like feline distemper or campylobacter.
  • Toxins: That “bad” mouse or toxins in spoiled food could be the culprit.
  • Inflammation: A common cause is hair rubbing around inside the stomach.
  • Ulcers: Perhaps a medicine damaged the cat’s stomach lining.
  • Cancer: Though uncommon, gut cancers can cause sickness.
Drooling is a telltale sign of vomiting and not of retching or regurgitation. Photo: gregwalters

Secondary vomiting can be caused by:

  • Pancreatitis
  • Liver diseases, such as cholangiohepatitis
  • Kidney failure
  • Overactive thyroid glands
  • Urinary blockage

The more signs you pick up on, such as excessive thirst, weight loss and poor appetite, the more likely it is the cat has an underlying problem that needs treatment:

  • One example might be irritation of fur in the stomach (hairballs) — this cat would need no intervention other than more regular brushings.
  • However, a cat with a recent history of taking arthritis medication or losing weight needs to be taken more seriously.

What Should You Do?

First, be aware that this information is for guidance only. If you are worried, contact the vet.

If your cat seems otherwise well and has thrown up, take the cat’s food away for 24 hours but leave fresh water.

The first meal you offer should be bland, such as a white meat (chicken, turkey, cod, rabbit) with a small amount of boiled rice. Give a small portion. If your cat doesn’t vomit, give food little and often over the next day or so before taking 2–3 days to transition back to normal food.

If your cat vomits repeatedly, brings food back or takes a turn for the worse, contact the vet.

Likewise, the cat who shows other signs of illness, such as those listed below, likely has an underlying problem of which the vomiting is a sign of ill health:

  • Drinking a lot
  • Poor appetite
  • Weight loss
  • Diarrhea
  • Struggling to pass urine
  • Change in behavior, such as unusual grumpiness
  • Dull coat
  • Offensive breath
  • A swollen belly

Even if the cat isn’t in danger of becoming dehydrated through vomiting, the underlying issue needs to be sorted by the vet.

When Is a Vet Trip Essential?

If you’re unsure what to do, take a look at this list. If you recognize any of these signs in your cat, see the vet:

  • Repeated vomiting: If this goes on for more than 4 hours, contact the vet.
  • Dehydration: If the cat can’t hold down water, there’s a risk of dehydration.
  • Losing fluid in diarrhea: Sickness and diarrhea makes dehydration more likely.
  • Blood in the vomit: This is a sign of internal bleeding and should not be ignored.
  • Dullness or lethargy: A cat who seems unwell or withdrawn could have gut pain.
If foreign bodies, such as pieces of stick, enter your dog’s gut, this may cause the dog to vomit. Photo: Fake Plastic Alice

Part 4: Uh-Oh! Why Is My Dog Throwing Up?

What’s the most disgusting thing your dog has eaten?

On second thought, don’t answer that.

One of the biggest differences between cats and dogs is that cats leave their vomit for their human to clear up, while dogs will gobble it up in the length of time it takes to fetch cleaning stuff.

From the “garbage gut” dog to the patient with a gut blockage, often the symptoms of vomiting are the same but the treatment very different:

  • For one, it’s a matter of withholding food.
  • For the other, major intestinal surgery.

So let’s take a dog’s-eye view of why your dog is throwing up.

Throwing Up vs. Regurgitation

First things first: Is the dog who presents you with a sausage-shaped version of breakfast actually vomiting? Probably not.

Regurgitation is a subtly different problem, which matters because it affects which investigative tests are required. Regurgitation is more passive than vomiting and is usually due to food sitting in the gullet (esophagus) that hasn’t reached the stomach.

Typically, the dog lowers his head and the food comes tumbling out in a sausage shape because it’s been sitting in the gullet. There’s no nausea or retching involved.

Pro tip: If you suspect your dog is regurgitating, record a video of it and show it to your vet.

Dog Is Throwing Up for Non-Gut-Related Reasons

A dog vomits. Therefore, he has a stomach problem — right?


Factors outside the gut can make a dog nauseated or cause vomiting. Some examples include:

  • Pancreatitis: Digestive juices escape from the pancreas and cause severe inflammation. This can be linked to a recent fatty meal.
  • Liver disease: When the liver fails to thoroughly detox the blood, the dog slowly poisons himself.
  • Pyometra: Pus in the womb causes bacterial toxins to enter the bloodstream.
  • Kidney failure: The kidneys fail to remove naturally occurring toxins from the blood, which build up and inflame the stomach lining.
  • Inner ear problems: When the balance mechanism is inflamed or infected, this results in nausea, similar to motion sickness.
  • Complicated diabetes: Ketone buildup leads to nausea and vomiting.
  • Addison’s disease: Severe electrolyte imbalances in the bloodstream cause vomiting.
  • Bladder obstruction: Retention of toxic metabolites cause nausea and vomiting.

Quite a problem list to whittle down — but it doesn’t end there.

Throwing Up Due to Gut Problems

Even this isn’t straightforward, as this list of possible causes shows:

  • Garbage gut: Scavenging spoiled food that the body then “rejects.”
  • Stomach infections: Food poisoning by any other name.
  • Systemic infections: Bugs such as distemper, parvovirus, coronavirus and leptospira cause the entire dog to become ill, of which gut signs are a part.
  • Stomach ulcers: Due to stress or caused by drugs eroding the lining of the stomach.
  • Inflammatory bowel disease: The causes of inflammatory bowel disease are a whole topic to itself. In a nutshell, this can be food allergy or intolerance, lack of fiber in the diet or stress.
  • Drug or toxin reaction: Anything that has contact with the gut wall has the potential to cause inflammation and vomiting.
  • Cancer: From localized tumors to general inflammation of the intestine, cancer is a rare cause of vomiting — but not one to be overlooked.
  • Foreign body: This one causes most vets the biggest headache. It is the nature of dogs to investigate with their mouths and to chew. This can lead to swallowed toys, yogurt pots, stones — you name it. If these get stuck in the gut, then the consequences can be very serious.

What to Do When Your Dog Throws Up

If your dog seems otherwise well but has vomited, then withhold food for 12–24 hours, but allow access to water.

Then give bland food for their next meal. However, if you are worried, go seek a vet’s opinion.

Indeed, take the dog to a vet if you see the following:

  • Blood in the vomit
  • Vomiting for longer than 4 hours
  • Unable to keep water down
  • Listless or lethargic
  • Also has diarrhea
  • Trying to be sick but bringing nothing up
  • Has other symptoms apart from vomiting

As you see, the reasons for a dog throwing up are many and varied, so for safety’s sake, hand the problem over to your vet.

When your dog experiences symptoms beyond vomiting, like lethargy and diarrhea, it’s time to see the vet. Photo: Kate Brady

Part 5: Diarrhea in Dogs and Cats

Diarrhea in pets usually results from an irritant occurring at the end sections of the small intestine or in the large intestine.

Because the digestive process hasn’t been completed, the moisture has not been removed from the feces, which is why it is expelled in a very liquid state.

The most common causes of diarrhea in dogs and cats are the same as vomiting:

  • Parasites
  • Foreign objects
  • Food irritants

Fat and skin from human scraps are often a cause of diarrhea in dogs, and shouldn’t be fed to pets, according to Dr. Carol Osborne, DVM.

She states, “If you’re not going to eat it, neither should your dog. You’re not going to eat the fat and many of you aren’t going to eat the skin or the scraps.”

Fat is harder for cats and dogs to digest, which can cause irritation in the colon resulting in diarrhea.

An obstruction in the lower end of the small intestine or in the colon can also cause diarrhea; an obstruction in this area of the digestive tract often causes small amounts of blood to be expelled rather than feces.

A puncture of the bowel caused by an obstructed object can cause the toxic contents of the intestines to spill into the abdominal cavity, causing a serious and sometimes fatal condition known as peritonitis.

In the following video, a veterinarian discusses the causes, symptoms and treatment of diarrhea in pets:

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What to Look For in Feces

If your cat or dog has diarrhea, examining the feces may give clues as to the cause.

  • Look for expelled foreign objects such as fabric or plastic.
  • Parasites often appear as white, noodlish objects.
  • Feces that is soft but otherwise normal typically indicates a minor colon irritation.
  • Fresh, red blood and mucus are often an indication of an injury to the colon, such as from an obstruction.
  • Thick, black, sticky feces may indicate an injury in the duodenum.
  • Severely runny feces accompanied by a severe stench may indicate that the feces was expelled before undergoing the complete digestive process in the small intestine.

If your cat or dog’s vomiting or diarrhea lasts for several days, you should bring your pet to the vet to have a thorough examination to determine the exact cause.

Next, we take an even deeper look at this common condition in dogs specifically.

Diarrhea may be a symptom of intestinal parasites. Photo: alecale35

Part 6: Recognizing the Warning Signs of Dog Diarrhea

How often does your dog get tummy upsets?

Notice the question is “How often?” rather than “Does your pet get tummy upsets?”

Why? Because diarrhea in dogs is a common problem.

So how do you know when your dog needs to see the vet or their tummy can be managed at home? And if you don’t feel the dog is sick as such, what’s the best way to settle the upset?

Cause and Effect

Even the cutest furbaby can have a penchant for cat poop (or worse!) or are sidewalk snackers when the opportunity arises.

It doesn’t take a genius to work out that eating a 5-day-old burger is going to end, er, explosively.

Likewise, that nose-down, sniff-along attitude means the dog is in constant contact with the ground. Just as we can pick up flu from touching objects coated in flu virus, dogs can pick up stomach bugs ranging from nasty viruses to bacterial infections — or even parasites.

Then there are the dogs for whom diarrhea is a symptom of a wider problem. It might be they have liver disease, pancreatitis or inflammatory bowel disease, all of which can develop diarrhea as a complication.

Red Flags

Be aware this article is for general interest only and not intended to replace 1-to-1, hands-on veterinary attention.

If you are worried about your dog, trust your instinct and always seek vet advice, regardless of the circumstances.

However, there are some red flag signs that should not be ignored, which mean it’s crucial the dog visits the vet. These include:

  • Blood: Bloody diarrhea can make a dog very ill very quickly, so please seek urgent attention. More on this later.
  • Vomiting and diarrhea: The double whammy of fluid loss from both ends quickly leads to dehydration.
  • Restlessness or pain: No one wants their pet in pain.
  • Abdominal stretches: When the dog adopts a “praying” stance, with their butt in the air to stretch their tummy, this can be a sign of pancreatitis. Best get this checked out.
  • Not drinking: The risk here is dehydration, if the dog is losing fluid in the diarrhea but not replacing it.
  • Unwell or lethargy: It might be the diarrhea is a symptom of a more significant problem that needs sorting out.
  • Diarrhea lasting more than 48 hours: The longer the diarrhea persists, the less likely it is to settle without treatment, as the balance of bugs inside the bowel is thrown out of whack.

Managing Uncomplicated Diarrhea at Home

OK, so your dog has a history of scavenging, and they raided the garbage yesterday.

Today, they have diarrhea but are still asking for breakfast. What should you do?

First, check the diarrhea for signs of blood. All clear? Good. (If you do see blood, go immediately to Part 5 of this article below, “Blood in the Diarrhea.”)

Now, are they bright and well, not vomiting, and asking for food? Good. If you aren’t unduly concerned for their overall health, here’s what you should do.

Monitor your dog for signs of lethargy. Photo: Free-Photos

Starve the Dog

Yep, that’s right. Withhold food for 18–24 hours.

This allows the gut to purge itself without adding “ammunition.” It also rests the bowel, allowing it to heal itself. Of course, during this time, allow free access to water so the dog doesn’t become dehydrated.

The purpose of starvation is twofold:

  1. Food causes muscular contractions of the bowel, with the effect that it “feeds” the diarrhea. When you withhold food, those muscular contractions ease and allow things to calm down.
  2. There’s evidence that feeding when the gut is inflamed is linked to the development of food allergies. Thus, if you offer Riffraff his regular food when his tummy is upset, there’s a small risk at a later date he’ll develop an allergy to one of the ingredients.

All being well, the dog “empties” and then doesn’t “go” for a while (their system is empty).

Reintroducing Food

The 2 rules for reintroducing food are:

  1. Little and often
  2. Bland food

Bland foods, such as white meats (chicken, white fish, turkey and rabbit), with an easy-to-digest carbohydrate (boiled potato, white rice or white pasta) are gentle on the gut, aiding its recovery.

Giving small meals regularly, such as 4–6 portions spread over the day, helps keep things low-key. Remember: The more the stomach is stretched (with a big meal), the greater the muscular contractions with the potential to rekindle diarrhea.

As a rule of thumb, feed the bland diet for 4–5 days. Once the dog has passed a couple of formed poops (albeit small ones because the food is highly digestible), take several days to slowly reintroduce the regular food.

Helpful Suggestions

So far, we haven’t mentioned pumpkin.

This is wonderful stuff that can ease constipation and firm up soft stools. This is down to the soluble fiber content, which helps regulate the gut and reset it to normal.

If you feel inclined, it’s fine to add a little pumpkin to the pet’s food and give nature a helping hand.

The other “goodies” that can help reset the bowel are probiotics.

When dogs have diarrhea, they lose some of the helpful bacteria that are necessary for digestion. Indeed, prolonged diarrhea results in a swing the other way, where harmful bacteria get the upper hand and keep the diarrhea going.

Feeding a good dog probiotic (and yes, it does have to be a dog formulation — your human probiotic yogurt drink isn’t going to help because we have different gut bacteria) once a day for 3–5 days can speed up recovery.

Be Alert for Deterioration

Watch carefully for signs the dog is getting worse. These include:

  • Repeated straining but nothing coming out
  • Blood in the diarrhea (If you see blood, go to Part 5 of this article below, “Blood in the Diarrhea.”)
  • The development of other symptoms, such as vomiting, lack of energy or coughing
  • General weakness
  • Not eating
  • No improvement after 2 days

If you notice these symptoms, visit the vet immediately.

Avoiding Diarrhea

You can also help your dog by cutting down on some of the risk factors for diarrhea, such as intestinal worms or infections against which there is a vaccine.

Regularly deworm your dog according to their individual risk:

  • For example, if you have a hunting dog who regularly eats carcasses, then weekly or monthly deworming would not go amiss.
  • However, a lapdog who lives mostly indoors should be fine with 3–4 times a year.

Keep up to date with your dog’s vaccinations, and if you are going on a vacation out of your usual area, speak with your vet about whether non-core vaccinations are advisable.

A sudden change of diet can also upset stomachs. If you want to change foods, take a few days to make the swap, gradually mixing in more of the new food and using less of the old.

Hopefully, you now feel more confident about how to handle those tummy upsets. Whether your pet needs to see the vet or can be managed at home, here’s a big “Get well soon” from us.

The cause of dogs suffering from bloody stools often remains unknown. Photo: smerikal

Part 7: Blood in the Diarrhea — And What It Means

The color red. Red lights. Red alert!

Red means bad things. When your dog poops red, that’s a scary thing.

Many dogs will show an occasional speck or a drop of blood while defecating. This should always be checked out.

But some dogs, often without a history of being sick, have very bloody diarrhea that can set people into panic mode.

Bloody Diarrhea

Seeing bloody stools in a dog is a horrible topic to discuss. You wake up stepping in something awful or you suddenly see your dog has very bloody diarrhea while you’re on your morning walk.

That’s why you call me, your veterinarian, at any hour of the night. But the blood doesn’t mean this is the end. I often need to calm people down because they think their dog is dying.

Multiple-Choice Question

What do you do if you find bloody diarrhea?

  1. Call the vet.
  2. Sit and worry.
  3. Wait several days to see what happens.


  1. Call the vet!

Your vet can tell you a great deal from a simple but thorough physical exam, as well as a thorough history from you. She can often determine how ill your pet is very quickly and what to do about it.

A Thorough History

Be prepared to answer a long list of questions as best you can.

You don’t always have all the answers because Mr. Eat-Garbage may have some sneaky secrets he doesn’t want to share, like what he eats when dining out, what his poop has looked like for the past 2 days and how his tummy has been feeling.

These are private matters — even for garbage eaters! Nobody likes to talk about their bathroom issues in public.

Questions Your Vet Will Ask

  • Has your dog been having diarrhea?
  • How long has the diarrhea been going on?
  • Is there any vomiting?
  • How long has there been blood in the poop?
  • Has he still been eating?
  • Is he lethargic?
  • Has this ever happened before?
  • Does your dog roam free?


Your vet may want to do some blood work, a fecal exam and radiographs if indicated.

Diagnostics and treatment depend on how debilitated your dog is and the level of dehydration. Many of these dogs are looking great even though their stool looks like a horror movie.

We often don’t find the reason behind an acute outburst of bloody diarrhea in a dog. If the bloody diarrhea occurred acutely and the dog has been otherwise in good shape and is not acting sick, we usually treat with supportive care.

The good news is that these dogs usually get better as fast as they have become sick.

No one really wants to talk about bloody stool, but your dog should get to the vet immediately if you see it. Photo: abbynormy

Supportive Care

Treatment may mean a short stay in the hospital for fluids and medications by injection, but many of these dogs can be sent home under your careful watch.

Treatment usually includes a short fast followed by small amounts of a bland diet for several days, medications to control GI signs, and monitoring of the dog’s demeanor and symptoms.

Hemorrhagic Gastroenteritis (HGE)

Some dogs exhibiting bloody diarrhea are also extremely sick and are suffering from a more serious form of bloody diarrhea called HGE. These pups usually exhibit:

  • Profuse, foul-smelling, bloody diarrhea
  • Poop that people describe as “raspberry jam” (culinary pathology is always gross but informative)
  • Anorexia and vomiting
  • Depression and abdominal pain
  • Dehydration

Diagnosing HGE

The physical exam, history and a quick blood test in the office — called a packed cell volume, or PCV — can differentiate HGE from a less serious attack of bloody diarrhea. Dogs with HGE require hospitalization, IV fluid therapy and more supportive care. They are very sick pups indeed.

Reduce Stress

  • Stress may play a part in diarrhea cases.
  • Boarding your dog can also lead to diarrhea, bloody or otherwise.
  • Rich foods or trash eating can certainly be a factor.
Diarrhea is just one symptom of cobalamin deficiency in dogs. Photo: colliefreund

Part 8: How Cobalamin Injections May Help With Diarrhea

Roy, a Rough-Coat Collie, was having a decidedly rough time with persistent diarrhea.

His caretaker had invested in blood tests and followed advice to date, and yet Roy was still sloppy in the stools department — and his person was getting impatient.

It wasn’t that we didn’t know what was wrong with Roy. He had inflammatory bowel disease.

His treatment involved:

  • A hypoallergenic diet: This drastically reduces the risk of food intolerance or allergy as a trigger for the lining of the bowel to become inflamed.
  • Pre- and probiotics: The nature of Roy’s diarrhea meant he had lost most of the bacteria helpful to digestion, and these needed replacing.
  • Antibiotics: Where the normal gut flora and fauna had been lost, other bacteria had invaded and flourished. The trouble was that these bacteria don’t help digestion and had to be gotten rid of so that healthy gut bacteria could flourish.
  • Steroids: The severity of Roy’s inflammation meant that he passed blood. This severe soreness needed settling down with anti-inflammatories, of which steroids were the first choice.

With Roy still in the doldrums despite the diagnostics and treatment, it looked like we’d have to add in an even stronger anti-inflammatory medication. But Roy’s human was unhappy and didn’t like the idea.

What to do?

Cobalamin for Bowel Health

It has long been recognized that cobalamin is essential for good bowel health.

Decades ago, for a dog with an upset stomach, vets often gave a shot of cobalamin to speed recovery. However, in the push for evidence-based medicine (EBM), this practice was stopped as “old school,” as it was anecdotal at best rather than based on hard evidence.

In a spirit of what goes around comes around, Roy was given an injection of cobalamin and asked to return the following week.

Only 3 days later, Roy’s human called, ecstatic on the end of the line. After weeks of horrid poop, that very morning Roy had passed a minor miracle of a perfectly formed poop. Whoop-whoop!

Reassessing our plans, we elected to give Roy 6 weekly cobalamin injections and then review his therapy after that.

A new nutraceutical tablet contains cobalamin in a form the gut can absorb when blood levels are low. Photo: sayuraam

Why Cobalamin Matters

The news gets better and better because cobalamin is actually a vitamin — Vitamin B12, to be precise.

This is a water-soluble vitamin and has several important roles in the body, including:

  • DNA synthesis
  • Fatty acid metabolism
  • Cell metabolism
  • Making new red blood cells

Symptoms that a dog with low cobalamin might show include:

  • Poor appetite
  • Anemia
  • Diarrhea
  • Vomiting
  • Failure to thrive
  • Dull, starry coat

As you can see, this humble vitamin is actually very important.

What Low Blood Levels Mean

When blood levels of cobalamin are low, then gut health dips and the dog is less able to absorb the goodness from food. When the bowel wall is healthy, it can process Vitamin B12 and absorb it.

Happily, there are lots of B12-rich foods out there, but in an ironic twist, it turns out that an unhealthy gut is least able to absorb the cobalamin. Worse than that, cobalamin only lasts half as long when the dog is deficient — talk about adding insult to injury.

In dogs, only 1% of the cobalamin in food is absorbed across the bowel wall by diffusion. Instead, to get cobalamin from the gut lumen into the blood depends on a special transport system in the last part of the small intestine.

At this location are special molecules that bind to cobalamin in the gut lumen and help transport it across the gut wall.

Unfortunately, this mechanism breaks down, like a car with an empty fuel tank, when blood cobalamin levels fall, meaning the body is less efficient at the very thing it needs to do.

This means that feeding a cobalamin-rich diet, while commendable, is unlikely to help very much.

The Answer

Giving cobalamin systemically, in the form of weekly injections for 6 weeks can tip the scales and get things going again.

Once the blood levels are raised, then the gut transport system for cobalamin starts working and everything starts to swing again.

The injections can sting, and occasionally patients develop a sterile abscess at the injection site, but these issues aside, there are no major side effects. However, it’s a fair bet the dog would prefer not to visit the vet every week for over a month.

Thankfully, there’s good news on the horizon:

  • For the first time, there’s a nutraceutical tablet available that contains cobalamin in a form the gut can process and absorb when blood levels are low.
  • You can give the supplement (Cobalaplex, made by Protexin) to the dog once a day at home and avoid the dreaded vet trips and needle.

Roy’s Tail Is Still Wagging

The great news is that Roy is still doing so well that we’re weaning down the dose of his steroids.

He’s maintained a solid poop on the hypoallergenic diet alone, now that the allergens have gone, and his bowel health is top-notch.

Of course, if your dog has diarrhea, then see the vet. But it is heartening to know that a simple vitamin may be what’s needed.

So if your dog has a tummy upset or even long-term diarrhea, spare a thought for the B vitamins — they could help turn the corner.

In the next section of this article, we’ll discuss long-term diarrhea.

Parasites and food allergies are just 2 of the many possible culprits behind long-term diarrhea in dogs and cats. Photo: marczero1980

Part 9: Long-Term Diarrhea in Dogs and Cats

Diarrhea is a symptom rather than a condition in its own right.

So when it comes to treating such cases, getting to the bottom of things to find the underlying cause is crucial.

If we can find the cause and treat it, we can improve both the pet’s and your quality of life.


Signs of diarrhea are self-explanatory: loose or liquid motions rather than a nice, firm, sausage-shaped stool.

Put simply: If you can’t pick it up easily, then it’s diarrhea.

If your dog has diarrhea, here’s a quick plea from a veterinarian: Take a look. It really helps to know if blood or mucus is present.

If you are really keen, there is even a Bristol stool chart that ranks feces on a scale from 1 to 7 for consistency (1 is rock-hard nuggets; 7 is completely liquid), which is all valuable information when it comes to deciding on the best course of treatment.


The causes of diarrhea are many and varied.


  • Food allergy or sensitivity
  • Bacterial infections (salmonella, campylobacter, etc.)
  • Parasites (worms, giardia, coccidian)
  • Inflammatory bowel disease (IBD)
  • Small intestinal bacterial overgrowth (SIBO)
  • Low cobalamin (Vitamin B) levels in the bowel wall
  • Lymphoma (bowel cancer, which is more likely in the cat)
  • Protein-losing enteropathy (PLE)
  • Eosinophilic enteritis

Disease outside the bowel:

  • Exocrine pancreatic insufficiency (EPI)
  • Low protein levels in the blood
  • Pancreatitis
  • Liver disease
  • Severe heart failure
  • Stress
If your pet’s loose stool doesn’t improve after a few days, see the vet — the cause may be more serious than you think. Photo: eiriknewth


There are so many causes of diarrhea that investigation requires a logical approach.

Your vet will take a detailed history and an account of the pet’s age and breed, recent changes of diet and contact with infectious agents.

If a puppy has long-term diarrhea, the immediate suspect may be a parasitic infection, and the most useful diagnostic test is fecal analysis. By looking for parasites, eggs and larvae under the microscope, sometimes a diagnosis is made, and appropriate treatment is started swiftly.

Adult animals with diarrhea fall into 2 groups:

  1. Self-limiting cases that get better in a few days
  2. Those with long-term diarrhea

Long-term diarrhea tends not to be straightforward, and a screening blood test may help rule out disease that is causing it.

If the panel and fecal analysis are normal, then next on the list is a blood test looking at bowel function. This checks that the pancreas is producing enough digestive enzymes, the bowel is not deficient in cobalamin (essential for healthy digestion) and there is no overgrowth of bacteria within the bowel lumen.

If these tests draw a blank, then either an ultrasound scan or an endoscopy may be appropriate to reach a diagnosis.

Ultimately, in hard-to-crack cases, a bowel biopsy should give a definitive answer, but this procedure is not without risk and should be discussed thoroughly with your vet first.


Key to treatment is identifying the reason for the diarrhea and addressing that issue.

These common conditions require the following treatments:

  • Food allergy: Hypoallergenic diet
  • Parasite infection: Fenbendazole (depending on the parasite)
  • SIBO: A corrective course of antibiotics
  • EPI: Supplement the pancreatic enzymes
  • IBD: Anti-inflammatory drugs, low-allergen diet
  • Lymphoma: Surgery and possibly chemotherapy


To prevent long-term diarrhea, seeking veterinary advice in the early stages is key. When ignored, a short-term tummy upset can become a long-term problem if the bowel’s natural balance becomes disturbed and its ability to digest food is knocked out of whack.

So if simple diarrhea doesn’t settle after a couple of days of a light diet, take your pet to the vet to get checked out.

My girl had not 1 but 4 types of infections that gave her diarrhea. Photos: Pippa Elliott
This Puggle had not 1 but 4 major problems that gave her diarrhea. Photos: Pippa Elliott/Petful

Part 10: Common Infections That Can Cause Diarrhea in Puppies

This section of the article was written by Dr. Pippa Elliott, BVMS, MRCVS.

As someone with a Puggle puppy, I’m all too familiar with poop.

My new fur-family addition came with several unwanted extras in the tummy department in the form of campylobacter, roundworms, tapeworms and giardia.

Well, 2 fecal analyses and 3 courses of treatment later, I’m relieved to say she now passes PFPs (perfectly formed poops).

A History of Infections

My puppy didn’t have the best start in life and picked up her infections by contact with feces in the unhygienic conditions she lived in. When dogs come into contact with poop, they can catch all sorts of diseases, especially the very young whose immune system isn’t strong enough to protect them.

My recent experience of anxiously awaiting the next bowel movement to see if there was any improvement helped me view puppy tummy upsets from the other side of the consulting room table.

It has taken nearly 4 weeks to go from bloodstained, mucoid diarrhea to PFPs, so have a little patience if your puppy’s poops aren’t perfect yet despite a course of treatment. It can take a while to get to the bottom of things because your pup might have more than 1 infection (or 4, in my pup’s case).

1. Worm Infections

Worms are top of the charts when it comes to puppy poop infections.

  • The granddaddy is roundworms (Toxocara), with the mother passing larvae onto her pups in the womb and via her milk. It’s safe to assume your pup has Toxocara and to worm repeatedly — those larvae hatch out regularly, especially during the first 6 months of life.
  • Tapeworms (Dipylidium) go hand in hand with fleas, so the pup with passengers of the jumping sort is almost guaranteed to have tapeworms. The worms in the gut produce egg packets that migrate out of the pup’s anus and causes extreme itchiness, so be vigilant to the bottom-obsessed youngster constantly scooting or trying to chew under the tail.
  • Whipworms (Trichuris) and hookworms (Ancylostoma and Uncinaria) are also common and easy to catch. The eggs are extremely hardy and can survive for years in the environment, so it’s easy for a puppy to accidentally pick up infection. The signs include watery, bloody diarrhea, with the diagnostic challenge being fecal analysis that often gives false negatives due to lack of egg shedding at the time of sampling.
That belly! She's doing better know after treatment.
That belly! My puppy is feeling much better now after treatment.

2. Protozoal Infections

Other common gifts passed from mother to pups (usually those kept in unhygienic conditions) are giardia and coccidian infections.

Giardia is a single-celled organism from the family of organisms that causes amebic dysentery in people. Again, the cysts can persist in a moist environment for many months, making infection common. There are at least 6 species of coccidian that affect dogs, of which Cryptosporidium is the biggest problem in puppies.

One problem with protozoal infections is the risk of reinfection in the same pet — the cysts can cling to fur, ready to be ingested when the pup washes himself.

3. Bacterial Infections

Did you know that, on average, 1 gram of dog feces contain 23 million fecal coliform bacteria? That’s a lot of bugs, all with the potential to cause stomach cramps, diarrhea and kidney disease.

From salmonella to campylobacter, several bugs can affect puppies.

These can cause debilitating diarrhea with the added risk that they can be passed onto people. Diagnosis of the individual bug and targeted treatment depends on fecal analysis.

4. Viral Infections

The deadliest virus on our list is parvovirus, with signs occurring 2–5 days after infection, including life-threatening bloody diarrhea and vomiting.

Parvovirus is the Schwarzenegger of the virus world and can survive against all the odds in the environment, with vaccination being essential to maintaining good health.

Distemper can also cause diarrhea amid a host of other symptoms such as coughing, sticky eyes, fever and vomiting.

Less dramatic is coronavirus, which causes diarrhea in pups because of their weak immune systems. But — provided they don’t become dehydrated — it in itself isn’t deadly.

Treatment of Puppy Diarrhea

If you see blood in the stool or your puppy is vomiting, contact your vet immediately.

Diarrhea can be deadly if your pet becomes dehydrated, so it’s important to keep his fluid intake up.

Check the gums to make sure they feel moist — dry-feeling oral membranes are an early sign of dehydration. Syringe in electrolyte solutions to keep hydration steady.

If the puppy is bright in himself, offer a bland diet of white meat with boiled rice or pasta, or a prescription diet designed for upset stomachs.

Straightforward diarrhea should settle within 48 hours, so if the problem persists, seek veterinary advice.


  • Small Animal Internal Medicine. Nelson & Couto. Publisher: Mosby. 3rd edition.