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Is Vitamin B12 for Dogs and Cats A Good Idea?

written by Dr. Jo de Klerk - Mar 29, 2021
medically reviewed by Dr. Christine Bishara, MD - Aug 4, 2021

Photo Credit: by Corinne Benavides,
Photo Credit: by Corinne Benavides,

Vitamin B12 is an essential vitamin for the body. It plays an important role in the production of red blood cells, as well as the routine functioning of the nervous system.

Most pets get all the vitamin B12 they need from their food. Unlike humans, who sometimes need a vitamin B12 supplement for a ‘boost’, healthy animals do not need any extra vitamin B12.

However, some ailments can lead to deficiencies in vitamin B12, and in these instances, it is necessary for a veterinarian to prescribe a course of vitamin B12 treatment to improve the blood levels and prevent detrimental effects on the red blood cells and nervous system.

What is vitamin B12?

Vitamin B12 is also known as cobalamin. It is a water-soluble vitamin which is absorbed from the intestine and excreted by the kidneys.

There are four, almost identical chemical forms of vitamin B12, known as vitamers, which are cyanocobalamin, hydroxocobalamin, adenosylcobalamin and methylcobalamin. Cyanocobalamin is the most common form used in vitamin B12 supplements and treatments.

Vitamin B12 plays an essential role in the metabolism of cells in the body. It is also a cofactor in DNA synthesis. However, its most important role is to ensure the normal functioning of the nervous system. This is achieved through playing a part in the synthesis of myelin, which coats many types of nerve cells. Finally, vitamin B12 also aids in the production and maturation of red blood cells in the bone marrow.

Most pets gain all the vitamin B12 they need from their diet, as animal-sourced foods, such as meat, fish, eggs and dairy, are rich in it. Therefore, a healthy pet, eating a balanced diet, does not need vitamin B12 supplemented in their daily lives.

Why do pets need vitamin B12?

Pets may develop ailments which lead to vitamin B12 deficiency, and it’s important to recognise a deficiency early to prevent detrimental effects on the body.

Even though ailments are usually the cause, there is one exception; some dog breeds have a genetic predisposition for an inability to absorb appropriate levels of vitamin B12. These dogs are generally healthy but may need vitamin B12 treatment throughout their life. Border collies, beagles, Chinese Shar-Peis and schnauzers are most commonly affected.

Gastrointestinal ailments are also a common cause of vitamin B12 deficiency. It is absorbed in the small intestine, so any condition which affects the small intestine will reduce vitamin B12 absorption from the guts into the blood. A condition called small intestinal bacterial overgrowth (SIBO) presents a particular challenge, as not only is the small intestine compromised, but the bacteria bind the vitamin B12, making it especially difficult to absorb.

Conditions affecting the pancreas, such as exocrine pancreatic insufficiency, pancreatitis, and pancreatic cancer, can also lead to vitamin B12 deficiency. This is because the pancreas cannot produce as much ‘intrinsic factor’ (IF). Intrinsic factor is a substance which plays a role in the absorption of vitamin B12 into the bloodstream, and therefore a reduced amount of it will decrease the ability of vitamin B12 to be absorbed. Cats are particularly affected by pancreatic ailments, as the pancreas is the only source of intrinsic factor in felines.

Kidney conditions may potentially also lead to a deficiency in vitamin B12. Since vitamin B12 is normally excreted through the kidneys in the urine, excessive amounts of vitamin B12 can be lost with kidney disease. However, some studies have found contradicting results, and therefore it is unknown whether vitamin B12 deficiency is truly a common finding in pets with kidney disease.

How do I know if my pet is vitamin B12 deficient?

Symptoms of vitamin B12 deficiency are relatively non-specific so it may not be obvious that your pet has a vitamin B12 deficiency. Common symptoms include:

- Reduced energy

- Weakness

- Inappetence

- Weight loss

- Disorientation

- Muscle wastage

- Diarrhea

- Seizures

A deficiency can be diagnosed with a simple blood test. Most veterinarians do not have the ability to measure vitamin B12 levels on the machine in the veterinary practice, so the sample is usually couriered to a referral laboratory. Therefore, it may be several days before you receive a result.

Vitamin B12 injections for dogs and cats

Since vitamin B12 deficiencies are frequently caused by malabsorption from the intestine, oral vitamin B12 supplements are ineffective. Therefore, the best way of treating your pet with vitamin B12 deficiency is with injections under the skin or into the muscle.

Injections are usually given every week for four weeks, or until the blood vitamin B12 levels normalise. After this, injections can be given on an as-needed basis. The frequency is usually determined by gradually decreasing vitamin B12 injections to every two weeks, then monthly, and routinely re-testing the bloods to determine the longest possible interval.

Where to buy vitamin B12 for dogs and cats?

Injectable vitamin B12 can be purchased with a valid veterinary prescription from We are a certified and trusted pharmacy, which provides several options for your pet’s vitamin B12 needs. offers injectable vitamin B12 at very competitive prices. Generic vitamin B12 at a strength of 1000mcg/ml is available in 10ml and 30ml vials and manufactured by Sterimax. It is also available in 5 x 1ml ampoules and manufactured by Deva Pharma from Turkey.

Vitamin B12 should only be used in animals under the guidance of a veterinarian, and therefore it is important to follow the dosage amount and regimen as prescribed for your pet.


Dr Jo de Klerk is a veterinarian and a writer. She works with all species and enjoys writing articles for websites and journals. In her spare time she likes to horse ride and spend time with her young family.


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