Vitamin B12 in Cats Benefits and Deficiency Symptoms

Vitamin B12 or cobalamin (contains cobalt), like the rest of the B complex vitamins, is a water-soluble vitamin that occurs naturally in certain foods, added to others, available as a dietary supplement or may medically be prescribed.

Some of the forms of this vitamin include methylcobalamin (mecobalamin), hydroxocobalamin, adenosylcobalamin, sulphitocobalamin, and cyanocobalamin. Only the methylcobalamin and adenosylcobalamin are the naturally occurring forms.

Common natural sources of cobalamin include fish, meat, liver, kidney, eggs, poultry, milk and products of milk.

Note that cats cannot make their own vitamin B12. Consequently, they depend on natural food sources that contain it or foods where it has been added.  Also, it can be supplemented orally or through subcutaneous injections.

As a carnivore, you would expect this pet not to lack this vital vitamin since its diet is largely meat. However, there are some disease and conditions which may cause a deficiency, forcing you to supplement it.

While healthy, according to the National Research Council of the National Academies, your cat should have 1.4 µg of cobalamin daily for a cat that weighs 9 pounds and whose daily calorie requirement is 250 calories.

NRC recommends that cat feeds to have 22.5µg per/kg while AAFCO recommends an amount of 20 µg/kg of feed for all cat classes ( i.e., for maintenance, lactating, or growing kittens).[1]

Finally, being water-soluble, it is usually excreted from this pet’s body through urine. Consequently, any excess amount is excreted this way.

Vitamin B12 for cats
Vitamin B12 for cats sources

Cobalamin or vitamin B12 for cats benefits

Some of its function in your feline’s friend body include the following:

  • It acts as a cofactor (together with folate or folic acid) for several enzymes that are involved in amino acids, fats, and carbohydrates metabolism.
  • It helps in digestion and it ensures that your feline’s digestive system is healthy.
  • It ensures a healthy nervous and immune systems
  • As AnimalBiome notes, “it is essential for healthy cognitive function.”
  • It helps in the formation and maintenance of red blood cells and the formation of proteins from amino acids.
  • It boosts appetite. According to the Texas A&M University Veterinary Medicine and Biological Sciences, it has “a pharmacologic effect as an appetite stimulant. Anorectic feline patients with cobalamin deficiency often start to eat again once they are being supplemented and appetite wanes once again when cobalamin is no longer administered.”

Deficiency causes

The first reason why deficiency may arise is a malfunction of some organs. Your cat’s pancreas, intestine, stomach, and liver are involved in the absorption and assimilation of cobalamin. Therefore, if any of these vital organs is not working properly, expect the normal absorption to be disrupted.

Secondly, the duration during which vitamin B12 is retained in this pet’s body is limited. Usually, about 13 days if it healthy and if it has GI diseases or other conditions that affect its health, the vitamin gets depleted faster, i.e., it can only be retained for as little as five days.

Thirdly, low b12 in cats can be caused by some genetic factors (noted in some breeds) or disease and conditions that will hamper absorption of this very important nutrient which include:-

  • Inflammatory bowel disease (IBD) or Crohn’s disease – chronic inflammation and irritation of the GI tract
  • Pancreatitis and exocrine pancreatic insufficiency – inflammation of the pancreas and lack of digestive enzymes produced by the pancreas respectively.
  • Intestinal lymphoma (cancers)
  • Extreme stress
  • Diuresis or disease that makes your feline friend drink more water and consequently pass more urine such as hyperthyroidism. Being water-soluble, most of it will be excreted with urine.
  • Cholangiohepatitis

Also, deficiencies in proteins, vitamin B6, the absence of thyroid, iron and dietary tannic may affect the absorption of cobalamin. [1]

Vitamin  B12 deficiency in cats symptoms

Owing to the important roles it plays, cobalamin deficiency in cats every so often comes with some signs and symptoms which include the following.

  • Lethargy
  • Loss of appetite and consequently weight loss
  • Vomiting
  • Diarrhea
  • Constipation
  • Increased possibilities of small intestinal bacterial overgrowth (SIBO)

Besides these symptoms, a deficiency can lead to anemia, nerve damage as well as gastrointestinal problems. This is the reason why this vitamin is vital for diabetic cats with neuropathy.

Furthermore, notes that “occasionally cats with a B12 deficiency may also have difficulty in walking or jumping and may show a little weakness in their back ends.”


If your pet shows some of these symptoms, discuss the issue with your vet. He or she may begin by measuring vitamin B12 level in blood. This level can also in turn help in showing if this animal’s gut is healthy.

Secondly, a microbiome test kit may help show bacterial status in your cat’s gut and this can be compared with a healthy one. Bacterial health status may indicate the possibility of a deficiency of cobalamin.

Finally, the concentration of serum or urine methylmalonic acid can be used to indicate the level of this vitamin in these pets.

B12 dosage for cats – oral and B12 shots for cats

Vitamin B12 comes as oral tablets (or capsules), crystalline solution, and intranasal forms with different concentrations or amounts of cobalamin content.

The availability and low cost of the cyanocobalamin form make it the most chosen option for supplementation.

If your cat has low amounts of cobalamin than required (below 400 ng/L), your vet may recommend vitamin B12 injection for cats or opt for oral one such as Cobalequin Cobalamin Supplement Vitamin B12,  a tiny chicken-flavored tab ideal for cats or dogs weighing below 22 pounds. It is safe for long-term use, and you can give it as a tablet or crush and mix with their food.

Cobalequin Chew Tabs
Cobalequin Chew Tabs

Alternatively, try Rx B12  with cyanocobalamin (a man-made form of vitamin B12) that comes solution or liquid forms.

Oral dosages  

The recommended oral cobalamin for cats is 250 µg daily for at least 12 weeks followed by a check on its serum concentration a week after the last dose.

However, various manufacturers may recommend different dosages. For example, the  Rx B12 normal dosage for “smaller animals, is one milliliter daily and it will be equivalent to one injection a month. Medium-sized animals would be 2 milliliters daily and for large-sized animals, 3 milliliters daily” notes

Injection dosages

However, oral vitamin B12 for cats will be ineffective if the cause is chronic GI, liver disease or digestive disorders as it will not be absorbed even if you give them high dosages. In such a case, your vet will opt for injections.

For shots, normal dosages will be about 250µg of cobalamin daily for 7 days then one monthly dose, all on a need basis. This might slightly vary depending on the exact weight on your cat.

For instance, the  Anivit B12 solution for injection 250 µg/ml available in the UK is often used. This is an intra-muscular or subcutaneous injection and your vet will guide you on dosages.

Side effects and interactions

Over supplementation is not known to cause any side effects except if your cat is hypersensitive to cobalt or the brand you are using has xylitol which sugar alcohol toxic to dogs and cats.

Possible drug interactions that may affect its absorption include colchicine, potassium chloride, and neomycin, and p-aminosalicylic notes


Cobalamin is unlikely to treat any underlying diseases and conditions such as pancreatitis, intestinal lymphoma or IBD. If your pet has them, your vet will recommend other treatments.

Also, we intend to look at the issue of cobalamin shots for cats including their cost, B12 for cats with IBD, diabetes, and pancreatitis in different posts.


The first way to avert a deficiency is treating or managing various diseases and conditions that may be causing it such as gastrointestinal problems or liver disease.

Secondly, besides the use of injection and oral vitamin B12 for cats, you should increase the amount of meat especially organ meat such as the liver if the deficiency is not due to digestive disorders.

Moreover, consider going for commercial cat foods since most of those available in the market have the required amounts of this vital vitamin.

Finally, if your cat suffers from chronic kidney disease (CDK) or conditions that require regular administration of IV fluids. Adding cobalamin in these fluids may also a way to boost its levels. Your vet should help you with this matter.

See also

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