Vitamin A Toxicity in Cats

High levels of Vitamin A alter bone metabolism and stimulate extra bone to be deposited, which can lead to severe joint stiffness.

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Feeding too much liver can cause a cat’s bones to fuse, a result of too much Vitamin A. By: eviltomthai

In these days of health supplements, it may sound bizarre to think of vitamins as being toxic, but in cats Vitamin A toxicity is a very real disease.

Let me share a case with a moving story behind it.

Dora, a petite tortoiseshell cat, could hardly move. Her bones had fused together from the vertebrae to her elbows, shoulders and hip joints — as though Dora’s skeleton was carved from a single block of wood.

The reason? Vitamin A toxicity.

Unfortunately, Dora’s caretaker fed the cat almost exclusively liver, mistakenly believing it was good for her.

This is where the heartbreak comes in: He had found Dora, a stray, waiting on the doorstep upon returning home from a hospital visit to his fiancée’s deathbed.

He recognized something of his fiancée in the cat’s eyes, and resolved only to give her the best of everything — with unfortunate consequences.

Symptoms of Vitamin A Toxicity in a Cat

Symptoms include:

  • Stiff joints
  • A peculiar way of sitting, with the front legs held out at a strange angle, described as a “kangaroo” stance

This stiffness often starts in the neck and makes it difficult for the cat to groom, and the coat gets starry and dull. Joint soreness can also make it uncomfortable for a cat to squat long enough to have a bowel movement, and some cats suffer from constipation as a result.

Many cats lose their appetites, which complicates things when trying to better balance their diet.

Causes

Liver and cod liver oil are especially high in Vitamin A, and cats who eat these daily are at risk.

High blood levels of Vitamin A alter bone metabolism and stimulate extra bone to be deposited.

If this continues for long enough, bony bridges form across joints and effectively fuse them together.

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Joint stiffness is a prominent symptom of Vitamin A toxicity. By: jonolist

Diagnosis

In Dora’s case, radiographs of her skeleton and a history of eating almost nothing but liver was sufficient to make the diagnosis.

In less clear-cut cases, blood tests can check on Vitamin A levels in the blood to give a definitive answer.

Treatment

Dora’s bones were already fused together when she was brought in for treatment.

She was treated with pain relief medications, and her diet was slowly changed into something more suitable (she was a liver addict by this stage).

In mature cats with a fully developed skeleton, simply changing to a balanced diet and reducing Vitamin A intake is all that is needed in the early stages.

If this is done before bone changes occur, the outlook is excellent.

Young cats who are still growing are a greater problem. Their actively growing bones are easily damaged by excess Vitamin A and can be left with a permanent problem, even after the diet is changed.

Prevention

Key to this is feeding cats a balanced diet.

If your cat likes liver, give it as a treat once or twice a week.

Vitamin A toxicity in cats can be avoided by following this simple rule for life: Moderation is fine; excess is bad.

Personally, I’m not a fan of cod liver oil, but if you feel compelled to give it to your pet, give it every other day rather than daily.

References

  • Polizopoulou, Kazakos & Patsikas. “Hypervitaminosis A in the cat.” J Feline Med Surg, 7: 363–368.
  • Coates. “Measuring Vitamin A in blood plasma and serum.” Can Vet J, 39(5): 261.

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This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed Nov. 2, 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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