4 min read

Thiamine (Vitamin B1) for Cats


By Aurus Sy

Published: 04/11/2023, edited: 04/13/2023

Reviewed by a licensed veterinary professional: Dr. Linda Simon, MVB MRCVS

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Thiamine, also known as vitamin B1, is a water-soluble and essential vitamin, which means that the body needs it to work properly. Thiamine in cats is crucial for maintaining optimal health, and felines in particular have a high dietary requirement for this vitamin. 

How much thiamine is required for cats, and where can your furry friend get it? Are cats more prone to thiamine deficiency or thiamine overdose? Read on to learn all about thiamine for cats.


Thiamine plays many important roles in the body, including maintenance of normal growth, maintenance of normal nervous system function, transmission of nerve impulses, carbohydrate metabolism and acetylcholine synthesis. 

Acetylcholine is a neurotransmitter or chemical messenger that is involved in different brain and body functions such as muscle control, memory, and attention. Carbohydrate metabolism is a process that ensures a constant supply of energy to living cells. This energy-producing process is key for the proper functioning of the heart and nervous system. 

Like humans, cats cannot produce thiamine; it is only synthesized in plants, fungi, and bacteria. In addition, the body does not store significant amounts of this vitamin; therefore, cats must get it through their diet consistently. This is especially important as cats need more thiamine than other animals—three times more than dogs, in fact!

So how much thiamine does a cat need? For commercial adult cat food, the Association of American Feed Control Officials (AAFCO) recommends a minimum of 5.6 mg/kg on a dry matter basis. Note that this refers to per kg of dry food, not per kg of body weight.

several protein rich foods such as raw meat, eggs, milk and nuts - Thiamine for Cats

Food sources

Thiamine can be found in various plant- and animal-based food sources, including:

  • Whole grains
  • Vegetables
  • Nuts
  • Legumes
  • Brewer’s yeast
  • Meat (beef, pork, fish)
  • Organs (liver, heart, kidneys)
  • Milk
  • Eggs

It’s important to note that the mere presence of thiamine in a food does not indicate its activity or bioavailability as it is highly susceptible to degradation or destruction during processing. High temperatures, neutral or alkaline pH, chlorinated water, and oxidation can all lead to the loss of thiamine, hence most manufacturers add thiamine to commercial pet foods to compensate for these losses. 

grey cat sniffing a pill in a veterinary worker's hand

Signs of thiamine deficiency in cats

It is not clear how prevalent thiamine deficiency in cats is; however, it can be life-threatening if not recognized. What causes thiamine deficiency in cats? Several factors can increase a cat’s risk for developing a deficiency, including inability to absorb or process thiamine due to gastrointestinal or liver disease, certain medications like diuretics that increase urinary loss, or diets with inadequate concentrations of thiamine.

As mentioned above, thiamine is easily lost through standard food manufacturing processes, and despite manufacturers’ efforts to compensate for these losses, thiamine-deficient commercial pet foods can still make it to consumers. In the past 10 years or so, there have been numerous recalls of commercial cat foods for suspected or confirmed thiamine deficiency in North America. In addition to processing, storage conditions and duration can result in thiamine loss. One study found that thiamine in dry cat food decreased 34% after 18 months of storage. Some pet foods also use sulfur dioxide or sulfite preservatives which inactivate thiamine. 

Aside from nutritionally incomplete commercial cat foods, unconventional and alternative diets can cause thiamine deficiency as well. These include homemade diets, vegetarian diets, and raw food diets. Certain species of fish and shellfish contain the enzyme thiaminase which destroys thiamine, thus an all-raw fish diet can lead to thiamine deficiency.  

What are the signs of thiamine deficiency in cats? A cat with thiamine deficiency will initially show gastrointestinal signs such as anorexia and vomiting before exhibiting the neurological signs most commonly associated with the condition. Symptoms of thiamine deficiency in cats include:

Treatment of thiamine deficiency

Thiamine deficiency can be fatal if not reversed. Treatment involves thiamine supplementation and a change in diet. If the deficiency is due to an unbalanced diet and a cat is not yet showing advanced clinical signs, then switching to a complete and balanced diet may be all that is needed to treat the condition.

Otherwise, a cat will also need thiamine supplementation administered orally, subcutaneously, or intramuscularly. The usual dose is 1 to 2 mg per lb (or 10 to 20 mg for an average cat) every 24 hours for 2 to 4 weeks or until signs abate. A full and rapid recovery is possible when thiamine deficiency is recognized and treated during the early stages. For more information, check out our guide to thiamine deficiency in cats.

Signs of thiamine overdose in cats

Due to lack of data, there is currently no known safe upper limit for thiamine for cats. However, because it is water-soluble, any excess amounts will be excreted in the urine and so there is very little risk of overdose. Moreover, excessive intake of thiamine has not been found to cause any adverse effects.

cat about to take a pill - Vitamin B1 for Cats

Thiamine supplements for cats

Thiamine is available in tablet, powder, and injectable forms and is also included in many B-complex vitamin preparations. Oral thiamine and thiamine injections for cats are often used to treat thiamine deficiency. However, supplementation of thiamine for cats eating a complete and balanced diet is likely not necessary unless they’re on medications that increase thiamine excretion or have a condition that impairs their ability to absorb the vitamin. 

Keep in mind that thiamine may interact with other drugs such as amprolium and neuromuscular blockers, so always talk to your vet before adding thiamine to your cat’s diet. 

It’s clear that thiamine plays a crucial role in feline health. While thiamine overdose is unheard of, thiamine deficiency can happen for a number of reasons, including being fed an unbalanced diet. 

The symptoms of thiamine deficiency can be expensive to treat. To avoid high vet care expenses, secure pet health insurance today. 

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