Understanding Diabetes in a Dog or Cat

The most obvious symptom of diabetes mellitus is increased thirst.

Is your cat drinking more water than usual? That may be a sign of diabetes. By: jahofker

Diabetes mellitus is a condition resulting in high blood sugar levels either because the body produces too little insulin or the tissue can’t use the insulin that is produced.

In cases of uncomplicated diabetes, the patient usually responds well to insulin injections that bring blood sugar levels back to normal.

The reason for a lack of insulin is problems in production by the pancreatic beta cells, which is the most common type of diabetes in pets. Tissue resistance to the effects of insulin occurs but is much less usual than in people.

It helps to understand the interplay between insulin and blood sugar levels. Cells need energy to function, and glucose provides this energy. This only works, however, if the glucose can get inside the cell, and for this, insulin is needed.

Insulin acts like a key to open the door of a locked cell, allowing glucose in. Without insulin, the door remains locked and the glucose cannot enter. This means the body must look elsewhere for sources of power, and it resorts to breaking down its own tissue, which in turn results in the formation of toxic waste products.


The most obvious symptom of diabetes is increased thirst. The pet drinks far more than normal, and you need to fill the water bowl more often.

If the pet is a cat who uses a litter tray, you will also find it necessary to empty the tray more often. Some pets start having nighttime accidents and a breakdown in house training.

Less obviously, the pet loses weight, and his fur becomes dull and unkempt. Cats in particular can show a bizarre neuropathy in their back legs where they walk flat-footed (known more correctly as a “plantigrad stance”). They lack energy, and their breath may smell sickly sweet. Left untreated, these pets gradually deteriorate to the point where they may start to vomit and eventually collapse.

Female dogs who haven’t been spayed are at an increased risk of developing diabetes. By: webmonster


Intact dogs and overweight cats are at increased risk of diabetes.

Age also plays a part, with diabetes being relatively rare in animals under the age of 7 years old. Some drugs, such as corticosteroids and the hormone tablet megestrol acetate, are also known to push an animal leaning toward diabetes into clinical disease.

Certain health conditions, such as hyperthyroidism in the cat and Cushing’s disease in the dog, can also nudge pets toward diabetes.


This is commonly made with a combination of blood and urine tests.

A high blood glucose level certainly points toward diabetes, but a single high result could just be the result of stress. Therefore the veterinarian will want to prove this is a true finding by running a glucose curve, which monitors blood glucose levels throughout the day.

Dipsticks tested on urine passed at home (i.e., not under stressful circumstances) also help diagnose diabetes.

A fructosamine blood test — an overview of blood sugar levels for the past 2 weeks — is yet another useful tool for confirming diabetes.

Watch how testing your dog’s blood sugar levels can be easy and relatively painless:


Treatment consists of eliminating any predisposing factors so that females then can be spayed. After that, if the pet remains diabetic, then once- or twice-daily insulin injections are highly successful ways of bringing a pet back to normal.

In addition, just as in people, diet plays an important role in making blood glucose levels more stable. Special diets that release energy slowly over the day are available, or indeed there is a high-protein diet for cats that is particularly appropriate for their metabolism.


Obesity is a risk factor for diabetes. It is thought that fat fills the beta cells that should produce insulin and in effect “suffocates” them, preventing insulin production. Thus keeping your pet at a healthy weight goes a long way in protecting her against diabetes.

Likewise, the hormones associated with estrus in the dog can make the body tissues resistant to the effects of insulin — spaying prevents this from happening.


  • “Insulin sensitivity in normal and diabetic cats.” Foldhahn & Martin. J Fel Med Surg, 1(2): 107.
  • “Current understanding of feline diabetes.” Rand. J Fel Med Surgery, 1(2): 143.


This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Oct. 11, 2018.

Dr. Pippa Elliott, BVMS, MRCVS

View posts by Dr. Pippa Elliott, BVMS, MRCVS
Dr. Pippa Elliott, BVMS, MRCVS, is a veterinarian with nearly 30 years of experience in companion animal practice. Dr. Elliott earned her Bachelor of Veterinary Medicine and Surgery from the University of Glasgow. She was also designated a Member of the Royal College of Veterinary Surgeons. Married with 2 grown-up kids, Dr. Elliott has a naughty puggle called Poggle, 3 cats and a bearded dragon.

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