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B12 Deficiency in Dogs and The Role of the Gut

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B12 Deficiency in Dogs and The Role of the Gut
Sweet Yuki the dog

B12 and Dogs

Vitamin B12 (also known as cobalamin) is important for many aspects of your dog’s health. It’s crucial for healthy nervous system and brain function, as well as for the formation and growth of blood cells. It’s also involved in intestinal health, so your dog needs B12 to maintain healthy digestion.


Most dogs get plenty of this nutrient from their food. B12 is found in meat (especially organ meat), fish, poultry, eggs, and dairy products. In a healthy dog, the pancreas, intestines, liver, and kidneys are all needed to properly absorb and store this B12. But in a sick dog, one or more of these organs may not be able to do its part.

Yuki the dog has B12 Deficiency due to cancer

What are the symptoms of B12 deficiency?

Because B12 plays an important role in the body’s absorption of iron, insufficient levels of this vitamin can lead to anemia. Dogs with a B12 deficiency and/or anemia may have one or more of the following symptoms:

  • lack of energy
  • weakness
  • reduced interest in play
  • loss of appetite
  • diarrhea
  • weight loss
  • lack of muscle mass
  • confusion
  • seizures

What causes B12 deficiency in dogs?

The primary cause of B12 deficiency in dogs is a problem with absorption. Certain breeds of dog are genetically predisposed to have difficulty absorbing B12: these include Australian shepherds, border collies, beagles, giant schnauzers, and Chinese Shar-Peis.

In all dogs, the pancreas plays a vital role in the extraction of B12 from food. Therefore, diseases of the pancreas—such as exocrine pancreatic insufficiency (EPI) and pancreatic cancer (as in Yuki’s case)—often lead to B12 deficiency. As a border collie mix, Yuki may also have been a carrier for Intestinal Cobalamin (B12) Malabsorption, the genetic mutation originally found in border collies. At the time, Holly didn’t know that genetic testing for this mutation was available.

Vitamin B12 also affects the interactions among bacteria living in the gut microbiome, and an unbalanced gut microbiome may be at the root of a B12 absorption problem. A good way to learn more about the community of microbes that live in your dog’s gut is with a microbiome test kit, which provides a detailed breakdown of all the bacteria in your dog’s microbiome, as well as how they compare to the bacteria found in healthy dogs.  

Disorders of the small or large intestine, including inflammatory bowel disease (IBD), can interfere with your dog’s ability to absorb many nutrients, including B12. In fact, a low B12 level is often used as an indicator for gastrointestinal disorders. Veterinarians generally recommend that dogs with chronic GI issues have their B12 level tested.

Can B12 supplements help a sick dog?

Can B12 supplements help a sick pet?

If your dog’s B12 level tests too low, your veterinarian will probably recommend either oral supplements or subcutaneous injections of the vitamin. The treatment is inexpensive and effective. And because B12 is water-soluble, any excess amounts are flushed out with the urine, so it’s very safe.

Holly’s veterinarian showed her how to deliver the subcutaneous injections at home, and soon after Yuki started getting the extra B12, her energy levels increased.

Note that if your dog has been diagnosed with IBD or another chronic GI disorder, treatments for that underlying condition may not be effective until a healthy B12 level has been restored.

More information

For more technical information about vitamin B12 and pet health, see this article from the Veterinary Medicine & Biomedical Sciences department of Texas A&M University.


To learn more about the gut microbiome of dogs, see our article on “Fecal Transplants for Dogs with Chronic Digestive Issues.”


(Cats need B12 too: here’s more information about B12 deficiency in cats.)

And if your dog has digestive problems, try our microbiome test kit and gut restoration supplements.

Let us know if you have questions or comments. If you liked this article please consider sharing it.

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