Cats and dogs and vitamin B12 deficiency

Like humans, cats and dogs need vitamin B12 for protein synthesis, tissue maintenance and blood cell formation. 

Vitamin B12, a water-soluble vitamin, is mainly acquired by eating food of animal origin but smaller amounts can also be produced by intestinal micro-organisms. Most commercial pet foods, including vegan or vegetarian diets, are supplemented with vitamin B12.¹ 

Vitamin B12 is a collective term for the cobalamins, of which cyanocobalamin and hydroxocobalamin are the main compounds. Cobalamins are cobalt-containing vitamins. Cobalamin can occur in any of several forms depending on the molecules linked to the cobalt ion (e.g. cyanide, hydroxyl or methyl groups as in cyanocobalamin, hydroxocobalamin and methylcobalamin, respectively).

Why do cats and dogs develop vitamin B12 deficiency?

Vitamin B12 deficiency is most likely to develop in animals with reduced cobalamin absorption due to gastrointestinal disease and in dogs with pancreatic enzyme insufficiency (which is more common in certain breeds).^1,2,3 It can also be due to inherited cobalamin malabsorption and disorders of the gastrointestinal microbiome.^1,4 

Cobalamin deficiency leads to various clinical and metabolic consequences, including vomiting, diarrhoea, weight loss, failure to thrive, nerve disorders, immunodeficiency, and intestinal changes including poor absorption of nutrients and vitamins (including cobalamin itself). In the most severe cases, dogs with hereditary conditions that affect cobalamin absorption – if left untreated – will die due to metabolic problems and immunodeficiency.

Treatment of cobalamin deficiency

After diagnosing cobalamin deficiency, a supplement may be prescribed with the aim of restoring appetite and well-being, allowing weight gain, and promoting normalisation of blood cell abnormalities.¹ Any underlying cause of deficiency, such as gastrointestinal or pancreatic disease, will also need to be addressed. 

Traditionally, cobalamin supplementation has been given by subcutaneous or intramuscular injection (using cyanocobalamin or hydroxocobalamin). There is a limited range of available veterinary authorised injectable vitamin B12 products, so a human authorised injectable product may be prescribed under the cascade (VMD 2021). 

There is now evidence that supplementation with an oral product is as effective as an injection and it is a simpler, less invasive and pain-free alternative to weekly injections. 

Oral supplementation may also be a more convenient and cost-effective treatment option for pet owners because some products are available as food supplements so can be purchased by pet owners without a prescription (e.g. Cobalin, Cobalaplex, Chemeys Vitamin B12 capsules). Their effectiveness will depend on the adherence of pet owners to the dosage regimen. Cobalamin supplements are well tolerated regardless of the administration route.⁵