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Thiamine Deficiency in Cats: 9 Signs to Look For (Vet Answer)

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Image Credit: Natata, Shutterstock
Last Updated on November 16, 2023 by Dr. Iulia Mihai, DVM MSc (Vet)

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Written by

Dr. Iulia Mihai

Veterinarian, DVM MSc

The information is current and up-to-date in accordance with the latest veterinarian research.

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Thiamine deficiency, or vitamin B1 deficiency, is a clinical syndrome associated with vascular lesions and nerve damage caused by an insufficient concentration of this vitamin in a cat’s body. This deficit is due to insufficient intake of vitamin B1 (part of the B complex group) in relation to the body’s requirements.

It is predominant in cats that consume large amounts of raw fish because these contain a compound that destroys vitamin B1. Thiamine deficiency can also occur in cats that consume unsupplemented commercial food, cooked food, or certain raw meats. Additionally, gastrointestinal and liver diseases can lead to thiamine deficiency.

Vitamin B1 deficiency is quite rare in cats but can be life-threatening if the clinical signs are not recognized by their owners in time. For this reason, you should know the clinical signs of thiamine deficiencies if your cat has a poor diet or eats large amounts of raw fish.

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What Is Thiamine Deficiency in Cats?

Thiamine, or vitamin B1, is a water-soluble vitamin (i.e., it dissolves in water) that is part of the B complex. It’s essential for your cat’s body and has the following roles:1

  • It helps transform carbohydrates into glucose.
  • It helps break down fats and proteins.
  • It maintains muscle tone at the level of the walls of the digestive tract.
  • It maintains normal growth.
  • It supports the health of the skin, eyes, fur, and liver.
  • It plays an essential role in maintaining a healthy nervous system.

Cats cannot synthesize thiamine, so their diet must contain this vitamin.2 When the food that they consume is low in vitamin B1, thiamine deficiency occurs.

a cat that feels sick and seems to vomit
Image Credit: chie hidaka, Shutterstock

What Are the Causes of Thiamine Deficiency in Cats?

Thiamine deficiency in cats can be caused by several factors:
  • Gastrointestinal disorders — These can lead to the inability of the body to absorb vitamin B1.
  • Liver diseases — These can lead to the inability of the body to process vitamin B1.
  • Consumption of raw fish — Some fish contain a substance that destroys thiamine.
  • Imbalanced diet — Cats must consume thiamine in their food or will suffer from deficiency side effects.
  • Over-processed food — Sometimes, the heating process used to prepare food can destroy thiamine.
  • Chemicals that may interfere with thiamine absorption — Examples of these chemicals are sulfites.


The 9 Signs to Look For in Thiamine Deficiency

Cats suffering from thiamine deficiency will initially present:
  • Lack of appetite (anorexia)
  • Vomiting
When the deficiency is severe, the following clinical signs may also occur:
  • Bending the neck in a downward position (cervical ventroflexion)
  • Dilated, fixed pupils
  • Muscle weakness
  • Tremors
  • Ataxia (unsteady gait/wobbly walk)
  • Paralysis of the eye muscles
  • Seizures

Neurological signs generally have a rapid onset and precede vomiting. In some cases, tetraparesis with developed rigidity may also occur.

sick cat vomiting the food
Image Credit: Tom Wang, Shutterstock

Thiamine Deficiency Diagnosis

The diagnosis is usually based on clinical signs and history. Common tests include a biochemical blood profile, a complete blood count, and urine analysis. A set of chest and abdominal X-rays can also be recommended, as it is part of the investigation (especially when vets want to rule out other health conditions with similar signs). Also, the response that deficient cats have when supplementing their diet with thiamine can be another way to make a diagnosis.

Thiamine Deficiency Treatment

The treatment is not difficult and includes:
  • Administration of injectable thiamine in the initial phase (for several days), then switching to oral thiamine for a month
  • Feeding your cat a well-balanced and high-quality diet
  • Limiting or suspending your cat’s raw fish diet

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Thiamine deficiency can be life-threatening for cats if it is not diagnosed and treated in time. The causes of this deficiency are certain gastrointestinal or liver diseases or eating raw fish or commercial food with low thiamine content. Common clinical signs include lack of appetite, vomiting, and nervous signs, such as twitching, incoordination, dilated pupils, etc. If you suspect that your cat has a thiamine deficiency, contact the vet.

Featured Image Credit: Natata, Shutterstock

About the Author

Dr. Iulia Mihai, DVM MSc (Vet)
Dr. Iulia Mihai, DVM MSc (Vet)
Iulia Mihai is a veterinarian with over 13 years of experience in pet pathology, laboratory, and cancer. She studied at the University of Agronomical Sciences and Veterinary Medicine of Bucharest, Romania (EAEVE member), where she worked in the laboratory of the faculty clinic after graduation. She has a master’s degree in equine and pet pathology and studied epithelial cancer for her Ph.D. Iulia has a passion for internal medicine and parasitology and started volunteering at the faculty’s clinic in her third year of college. She has worked in a couple of veterinary clinics over the years as an internal medicine specialist. She enjoys writing and teaching people about cat nutrition, behavior, and disease prevention and treatment.

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