What causes thiamin deficiency in cats?

The cause of thiamin (or thiamine) deficiency in cats is a lack of sufficient quantities of thiamin in a domestic cat’s diet. Why is there a lack of thiamin? That’s the real question.

Ventroflexion in a cat which can be caused by thiamin deficiency. Photo: Vetgirl.

Thiamin is labile

“Labile” means liable to change; easily altered. In other words, although thiamin is present in both animal and plant tissue (liver, whole grains and yeast being the richest sources) it changes and becomes inadequate for the purposes of a cat’s diet. The amount of preformed thiamin in manufactured pet foods is very low. Therefore it is added as a supplement.

Commercial cat food or not?

So if a cat guardian feeds their cat decent commercially prepared cat food their cat will get enough thiamin. The problem occurs when cat owners fail to do this. They feed their cat scraps of human food, perhaps, or poorly prepared homemade raw cat diet, or raw fish and shellfish because they think it is good for their cat and their cat likes it.

But raw fish contains high levels of thiaminase which is “an enzyme that metabolizes or breaks down thiamine into two molecular parts”. In other words, it breaks down the thiamin rendering it less than useful for cats. A domestic cat fed on raw fish suffers from thiamin deficiency and has the following symptoms: anorexia, lethargy, neurologists signs (the nerves fail to work properly) and muscle weakness which is shown first as ventroflexion of the neck. “Ventroflexion” is when the neck forces the head to be stuck in a downward position (the head droops).

Thiamin deficiency causing feline ventroflexion – head droop.

Examples of other causes of ventroflexion are hypokalemia, hyperthyroidism, and chronic renal disease.

Some other articles


Thiamin is vitamin B1. It is a water soluble vitamin. It is an essential co-enzyme in a number of metabolic processes. “Metabolic” refers to metabolism which is the chemical processes which keeps animals alive. A “coenzyme” is a non-protein compound that binds with an enzyme to catalyze a reaction (a chemical process).

Michael Broad

Hi, I'm a 71-year-old retired solicitor (attorney in the US). Before qualifying I worked in many jobs including professional photography. I have a girlfriend, Michelle. I love nature, cats and all animals. I am concerned about their welfare.

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