Could My Cat Have Thiamine Deficiency?

If your cat has suddenly stopped eating, started wobbling, or is holding their head in a strange downward curl, thiamine deficiency (a shortage of vitamin B1) could be the reason. It sounds obscure, but it’s more common than you’d think, and it can escalate from subtle to serious in just a few days. Caught early, most cats respond remarkably well to treatment.

Here’s what you need to know.

What thiamine does for your cat

Thiamine (vitamin B1) is a nutrient your cat’s body can’t make on its own. It has to come from food. And it’s not optional: thiamine is what the brain and nervous system use to convert carbohydrates into energy. Without it, nerve cells essentially start to starve.

Cats are especially vulnerable because they have higher thiamine requirements than most animals. Their bodies also don’t store much of it, so a deficient diet can cause problems faster than you might expect, sometimes within just a few weeks.

Signs of thiamine deficiency in cats

The neurological signs tend to show up in a specific progression. Early on, it can look minor. By the later stages, it’s a medical emergency.

• Loss of appetite: Often the first thing owners notice, easy to miss or explain away.
• Ventroflexion of the neck: This is the hallmark sign, where the head and neck curve downward in a distinctive hunched posture. It’s caused by muscle weakness from nerve dysfunction.
• Wobbling or loss of coordination: Your cat may stumble, fall sideways, or struggle to walk straight.
• Dilated pupils: The pupils appear unusually large, even in normal lighting.
• Star-gazing: The head is thrown back and upward, a sign the nervous system is in serious distress.
• Seizures: In advanced cases, thiamine deficiency and seizures go hand in hand. This is a neurological emergency.

If you’re seeing any combination of these signs, especially ventroflexion or seizures, don’t wait. Call your vet immediately.

The diet trap: foods that cause thiamine deficiency

Most cases of thiamine deficiency in cats trace back to something in the diet. Here’s where it goes wrong:

Raw fish and all-fish diets

Raw fish contains an enzyme called thiaminase, which breaks down thiamine before the body can use it. Cats fed a diet heavy in raw fish, or an all-fish diet, are at real risk. Cooking deactivates thiaminase, but many raw feeders don’t realize fish is the exception to the rule.

Homemade diets

Homemade cat food is well-intentioned, but getting the nutrient balance right is genuinely hard. Thiamine is heat-sensitive, so even cooked homemade meals can fall short if they’re not carefully formulated. If you’re making your cat’s food at home, a board-certified veterinary nutritionist can help you get it right.

Commercial cat food recalls

It’s happened more than once: commercial cat foods recalled because of inadequate thiamine levels. Thiamine degrades during processing, and if manufacturers don’t add enough back in, cats eating that food can develop deficiency over time. It’s worth checking the FDA’s pet food recall database periodically, especially if your cat’s food isn’t a major brand.

Diagnosis and treatment

Your vet will start with a physical exam and a thorough history of what your cat has been eating. Because thiamine deficiency mimics other neurological conditions, they may run blood work and urine tests to rule out other causes. In some cases, advanced imaging (like an MRI, a detailed scan of the brain) may be recommended.

Treatment is thiamine supplementation, given by injection for faster absorption in moderate-to-severe cases, or orally for milder ones. The response can be striking: many cats start improving within 24 hours of receiving thiamine. Cats with seizures or severe neurological signs may need hospitalization for supportive care, IV fluids, and close monitoring while they stabilize.

The earlier treatment starts, the better the outcome. Cats caught in the early stages often make a full recovery. Those who reach the seizure stage may still recover well, but the road is longer.

How to prevent thiamine deficiency in cats

Prevention is straightforward once you know what to watch for:

• Feed a complete and balanced commercial cat food from a reputable manufacturer that meets AAFCO nutritional standards
• If you feed raw, avoid making fish the dietary staple. If fish is included, cook it first to deactivate thiaminase.
• If you make homemade cat food, work with a veterinary nutritionist to formulate it properly
• Check the FDA pet food recall list a few times a year and sign up for recall alerts
• Mention your cat’s diet at annual vet visits so your vet can flag any nutritional red flags early

Does pet insurance cover thiamine deficiency?

A severe case can mean emergency vet visits, hospitalization, imaging, and injectable treatments. The costs add up quickly.

Thiamine deficiency is covered under Lemonade Pet illness coverage, as long as it’s not pre-existing and develops after the 14-day illness waiting period has passed. If your cat is already showing neurological signs, coverage won’t apply to that illness. The time to enroll is before something goes wrong, not after.

Before we go

Thiamine deficiency is genuinely scary to watch unfold, but also genuinely treatable when you act quickly. If your cat’s neck is curling down, their walk is off, or they’ve stopped eating without a clear reason, don’t second-guess it. Get to a vet. And if you’re feeding a raw-fish-heavy or homemade diet, this is a good moment to talk through the nutritional details with your vet before a problem starts.

Frequently Asked Questions

A few quick words, because we <3 our lawyers: This post is general in nature, and any statement in it doesn’t alter the terms, conditions, exclusions, or limitations of the policies issued, which differ according to your state of residence. You’re encouraged to discuss your specific circumstances with your own professional advisors. The purpose of this post is merely to provide you with info and insights you can use to make such discussions more productive! Naturally, all comments by, or references to, third parties represent their own views, and Lemonade assumes no responsibility for them. Coverage may not be available in all states. Please note that statements about coverages, policy management, claims processes, Giveback, and customer support apply to policies underwritten by Lemonade Insurance Company or Metromile Insurance Company, a Lemonade company, sold by Lemonade Insurance Agency, LLC.  The statements do not apply to policies underwritten by other carriers.