Thiamine Deficiency in Cats: Signs, Causes, and Prevention

What causes it

Most cases come down to diet. These are the main causes vets see.

• Raw fish and shellfish. Some raw fish, especially freshwater fish, and some shellfish such as clams contain an enzyme called thiaminase. It destroys the thiamine in the meal. Cooking breaks the enzyme down, and so does the heat of canning, so the fish in canned cat food is not a thiaminase risk.
• Homemade diets. Home recipes often lack the right amounts of vitamins, including thiamine, unless a veterinary nutritionist has designed them.
• Meat preserved with sulfites. Sulfur dioxide and sulfite preservatives destroy thiamine. Cases have been reported in cats and dogs fed fresh pet meat treated this way.
• Faulty commercial food. Too much heat during drying or canning, or a mistake in the recipe, can leave a food short of thiamine. One outbreak in 17 cats was traced to a defective dry food. In a US study of 90 canned cat foods, about 13 percent had less thiamine than the recommended minimum.
• Long periods without food. Cats that have gone hungry for weeks can run low.

Thiamine in stored food also breaks down slowly. One study found that levels in dry cat food dropped over a year, whether the food was kept at room temperature or frozen.

Signs to watch for

Early signs are easy to miss. A cat may eat less, seem tired or vomit, and many other illnesses cause the same signs. In kittens, poor growth can be a clue. Signs that the brain is affected often follow, sometimes quite suddenly. Owners may notice some of the following.

• Wobbly or drunken walking and trouble keeping balance
• A head tilt, or leaning and falling to one side
• Flicking movements of the eyes
• The head and neck bent down, with the chin tucked toward the chest
• Dilated pupils, poor vision or bumping into things
• Dullness or confusion
• Head tremors that show up when the cat reaches for something, such as its food bowl
• Seizures, which may come in clusters

Other problems can look similar. Low blood potassium, an overactive thyroid, inner ear disease, infections and some poisons can cause a wobbly walk or a bent neck. Your vet can tell them apart with an exam and tests.

When it is an emergency

See a veterinarian the same day if your cat suddenly walks as if drunk, tilts its head, loses its sight, cannot stand or has a seizure. A seizure that lasts more than five minutes, or several seizures close together, needs emergency care at once. Once brain signs appear, the condition can get worse quickly, and without treatment it can cause lasting damage or death. Early treatment gives the best chance of a full recovery.

If you can, bring the food packaging or write down exactly what your cat has been eating. Include treats, raw foods and anything homemade. This helps the vet a great deal.

How vets diagnose it

The vet will ask in detail about the diet and examine the nervous system. Blood tests help rule out other problems, such as low potassium. An MRI scan of the brain can show changes typical of thiamine deficiency, although a normal scan does not rule it out. Tests that measure thiamine exist, but reliable ones for cats are not available in every country.

Because of this, vets often start treatment when the history and signs fit. A quick improvement after thiamine is given supports the diagnosis.

How it is treated

Treatment means giving thiamine, by injection, by mouth or both, for a period the vet decides. The cat also moves to a complete and balanced diet. Cats with seizures or severe signs may need a hospital stay, fluids and medicine to control the seizures.

Many cats start to improve within a few days. In one group of affected cats, most survivors recovered within two weeks and were normal or nearly normal two months later. A few took longer, sometimes several months. The sooner treatment starts, the better the outcome tends to be. Your vet will tell you how long to continue and when to come back for a check.

How to prevent it

Feed a commercial food labeled as complete and balanced for your cat's life stage as the main diet. Keep raw fish and raw shellfish off the menu. Cooked fish is free of the enzyme. It is not a balanced meal on its own, so it works best as an occasional treat.

If you want to feed a homemade diet, ask your veterinarian about a recipe from a veterinary nutritionist. Recipes found online are often incomplete. Many vets also advise against raw diets in general, since they can carry germs that infect cats and people.

Store food in a cool, dry place and use it before the best-before date. Keep an eye on pet food recall notices in your country. If your cat stops eating for more than a day, call your vet.

Other pets and people

Thiamine deficiency is not an infection. It cannot pass from a cat to other pets or to people. Other animals eating the same food can still be affected. If the diet is the likely cause, watch your other cats closely and ask your vet whether they should be checked too.

Rescued and newly adopted cats

Cats found on the street may have gone hungry for a long time. Starvation can leave a cat low in thiamine, and the problem can show up once regular meals start again. For this reason, a vet may add thiamine and other vitamins when refeeding a very thin cat.

At Paw Squadron, the first stops after every rescue are the vet and a bath. Each animal has a checkup, deworming and treatment against fleas and other parasites. Before adoption, every animal also gets vaccinations and a microchip.

At home, a steady complete diet keeps the risk low. Ask what your new cat has been eating and change foods slowly. If you have questions about settling in a new cat, our FAQ is a good place to start, and you can find more care guides in PawPedia.