B12 vitamins, liver and anemia.

Find out why your FIP cat needs B12

In our FIP Advisory and Care group, we routinely advise our members to request B12 injections, and/or B12 supplementation. Here is a primer on B12 (a.k.a. cobalamin) that will explain why it is essential for your cat's health to maintain adequate levels of B12.
Please note: this article focuses on the benefits of adding B12 vitamins as supportive care to the main FIP treatment.

What is B12?

b12 for catsVitamin B12, also called cobalamin, is the generic name for a group of compounds having vitamin B12 activity. One distinctive feature of these compounds is a 4.5% cobalt content, hence the name ‟cobalamin" (cobalt + vitamin).

Where does it come from?

B12 is derived from foods of animal origin such as meat, liver, fish, and eggs. Most commercial cat foods cover the daily B12 needs of a healthy cat. A cat suffering from FIP, however, likely requires supplementation.

How does the body process B12?

Vitamin B12 is stored principally in the liver. Other storage sites include the kidney, heart, spleen, and brain.

Even though vitamin B12 is water soluble,  tissue half-life (how long it stays in the body) averages 13 days in healthy cats and is reduced to approximately 5 days in cats with gastrointestinal diseases or poor overall health. This means that if your cat has FIP, his B12 reserves can be depleted rather quickly.

The rate of absorption is slow; peak blood concentrations of the vitamin are not achieved for 6 to 8 hours after an oral dose. Also, it is one of the most difficult vitamins to absorb, and it requires normal function of the stomach, pancreas and small intestine. Cats with FIP often see their digestive functions altered by the progression of the virus. Therefore their ability to absorb the B12 is also compromised.

When you buy B12 as an oral supplement, we recommend you choose Methylcobalamin rather than Cyanocobalamin as the source. Methylcobalamin is a naturally occurring form of vitamin B12. Cyanocobalamin is a synthesized form of the vitamin and is the most widely used form of cobalamin in clinical practice because of its relative availability and stability. When your cat gets a B12 injection, it's the cyanocobalamin version.

What does B12 do?

B12 has several functions, all of them an integral part of a healthy immune system:

- B12 promotes red cell synthesis (the development and maintenance of red blood cells). Adequate levels of B12 are required to prevent anemia.
- B12 maintains nervous system integrity (nerve cells and normal myelination –the fatty sheaths that cover and protect nerve endings). It is essential for nerve and cognitive functions.
- B12 keeps the intestines healthy for the proper digestion and absorption of food, as well as the metabolism of carbohydrates and fats. That is a bit of a catch-22 because B12 is essential for the intestines to be able to function optimally, but they cannot absorb it (from the food) when they are damaged or diseased.

What are the signs of B12 deficiency?

Clinical signs of B12 deficiency include nausea, vomiting, loss of appetite, poor absorption of food (malabsorption syndrome), constipation, gas, weight loss, fatigue, lethargy, abdominal pain, and diarrhea. Some of the signs here are very familiar and are frequent side effects of FIP. They can be improved if your cat receives adequate amounts of B12.

In addition, B12 deficiency is associated with weakness in the limbs and impaired cognitive functions. Again, these are signs frequently observed when FIP affects the nervous system.

The big B12 catch-22.

1 – The cycle of depletion.
FIP is an inflammatory disease that impairs several functions of the body including the GI (gastrointestinal) tract. Liver, spleen, and pancreas are often affected. With an impaired immune system, the liver will become depleted from B12 reserves very rapidly. At the same time, B12 insufficiency in the liver leads to shrinking of the intestinal cells and malabsorption of nutrients (including B12 itself), leading to a cycle of worsening B12 deficiency. This is the catch-22 we discussed earlier in the article.

2 – The looming risk of anemia.
RBC production is impaired, and your cat becomes anemic. B12 deficiency inhibits and decreases the body's ability to produce blood and increases blood cell destruction. In short, while B12 levels plunge, your cat becomes anemic. Once your cat becomes anemic, his ability to fight the virus (or anything else) decreases considerably.

3 – Further weakening of immune resistance against FIP.
It is important to stress that insufficient levels of B12 raise susceptibility to infections and diseases, and are very harmful to the nervous system which in turn can cause neurological disorders and severe and sometimes irreversible nerve damage. In fact, cobalamin deficiency is a common cause of metabolic encephalopathy, one of a number of forms of encephalopathy associated with a primary disease (such as FIP) that causes interference with normal brain function and blood-brain barrier mechanisms. Clinical signs are indistinct and include lethargy, depression, ataxia, anorexia and intermittent vomiting, and in severe cases, can induce neurological disease and blindness in cats.
It is well documented that FIP cats are often anemic or borderline anemic, and some exhibits neurological signs of the disease. This is another aspect of the catch-22 backlash: without appropriate levels of B12, the effects of FIP may worsen, and because of FIP, your cat's ability to retain adequate reserves of B12 is diminished. It's a no-win situation unless you break this vicious circle and supplement the much-needed vitamins.

Treating hypocobalaminemia (B12 deficiency).

b12 injectionB12 injections.
Cobalamin is readily available over the counter in most countries. The recommended dose of cobalamin is 250 µg/cat by subcutaneous injection in cats up to 5 kg bodyweight. For FIP cats, we recommend a weekly injection until the anemia resolves and RBC values are stable. B12 can also be administered with subcutaneous fluid therapy. This method may be easier on your cat – B12 injections sting!

B12 oral supplements.
Methylcobalamin should be used because it helps the liver function much more efficiently. B12 supplements sold for humans are suitable for cats. A good starting dose would be 500mcg (0.5mg) per day, but you can give up to twice as much. It may sound high, but in reality, only a small percentage is absorbed. Consider a cat-specific multi-vitamins supplement that also contains iron (for anemia).

Don't underestimate natural sources of B12: feed your cat a little fresh meat, liver, fish - about a tablespoon a day if you can. A little goes a long way, and your cat might just like the treats. For comprehensive nutritional recommendations, please check out our "What to feed an FIP cat" article.

How can B12 improve my cat's overall well-being?

The improvement of your cat's health can be measured by blood tests, hematology and/or chemistry panels. However, you should notice changes in your cat's everyday behavior: increased energy, less lethargy, better appetite. It is important to remember that cats don't understand they are sick, or why they are sick. They have a vague sense of being unwell, and that is all they know. The addition of B12 to their treatment protocol may help lessen their discomfort and improve their quality of life.

Can B12 help cure FIP?

No. It does not. B12 is NOT a cure for FIP. But it supports essential functions of your cat's immune system. If you want to give your cat a chance to cope with the virus, you need all the help you can get. You cannot reasonably expect a positive outcome with the primary treatment if you do not do all in your power to maximize the chances of success.

In conclusion, FIP management is not just about administering a primary treatment, whether it is PI or FOI, etc. If your cat is to have a chance at survival, you, as your kitty's guardian, have to optimize the immune system and keep it running as efficiently as possible. Given the magnitude and the virulence of FIP, it is not an easy task. All us owners can do is fight as hard and as long as we can with every weapon in our arsenal. Everything counts in this battle, and B12 is an integral tool in the fight. You never know what seemingly small, but ultimately significant, course of action may make a big difference in the end. Give your cat a fair chance.


B12 vitamin is easy to procure. Injectables (as cyanocobalamin) can be done at your vet's office at home (if you know how to do it). B12 is routinely sold in pharmacies, but prescription is needed. First get an injection to give your cat an immediate boost.
Oral supplements can be bought online or your local health store. Look for Methylcobalamin capsules for B12 only or B-complex formulas.
You can get cat-specific supplements such as Pet-tinic (US), Hemovet or Tonivit (EU), Thorne's B-Complex vet, etc. This list is not exhaustive.
High calories nutritional paste contains mineral and supplements including B12 that are suitable for finicky cats with mild anemia.