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What does Vitamin B12 do for dogs? Dog with ball in mouth running in the grass

What Does Vitamin B12 Do for Dogs?

Behind every spirited game of fetch with your pup, there's a symphony of nutrients working diligently to help support their bodily functions. One standout player? Vitamin B12.

As veterinary professionals, it's our role — and, dare I say, my passion — to dive into the nitty-gritty of these essential nutrients. So get ready to take your curiosity for a walk! Today, we’re journeying into the world of B12 to discover the role this vitamin plays in your dog's well-being.

What is vitamin B12?

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays a pivotal role in the functioning of the brain and nervous system, as well as the formation of red blood cells.

This critical micronutrient is not produced by the body and must be obtained through diet. It's naturally found in animal-based foods — for dogs, B12-rich sources include meats like beef and poultry, and especially organ meat.

But some pets, especially those with gastrointestinal disease, may not be able to absorb B12 effectively. This can lead to a deficiency and associated clinical signs.

Why B12 matters to dogs

At a cellular level, vitamin B12 performs many important functions (see here for even more nerdy details). Your dog’s body relies on B12 for:

  • Nerve function: B12 helps form myelin, which coats and protects the nerves. Think of B12 as the “insulation” for your dog's nerve “wires”. Without proper insulation, signals can get lost or misdirected, leading to neurological problems.
  • Cell growth and replication: B12 is involved in these critical processes, helping every cell in your pup's body replicate accurately.
  • Metabolism: B12 is vital for the metabolism of fats, protein, and carbohydrates. It helps to convert these nutrients into energy, ensuring dogs remain lively and active. (So, those 2PM zoomies? Thank B12!)
  • Red blood cell formation: B12 plays a crucial role in hematopoiesis, AKA the formation of red blood cells. These cells transport oxygen and nutrients throughout the body, ensuring every part of your pup — from their nose to their tail — is functioning optimally.
  • Promotes gastrointestinal health: B12 is integral to gut health, ensuring efficient digestion and nutrient absorption.
  • Boosts appetite: Adequate levels of B12 can promote a healthy appetite in dogs. This is partly due to its role in energy metabolism and gastrointestinal health. When the body efficiently processes nutrients, and the GI tract functions optimally, this well-oiled machine naturally promotes a consistent and healthy appetite.
Dog and human doing a shake or paw agreeing together that B12 is essential

What can cause B12 deficiency in dogs?

Vitamin B12 deficiency in dogs can often be traced back to issues concerning the gastrointestinal (GI) tract.

For instance, Exocrine Pancreatic Insufficiency (EPI), a condition where the pancreas doesn't produce sufficient digestive enzymes, can hinder the absorption of crucial nutrients, including B12. Similarly, Inflammatory Bowel Disease (IBD) can lead to reduced capability to absorb nutrients.

Other culprits include intestinal parasites or bacterial overgrowth. In fact, any dog with chronic intestinal issues is at risk for B12 deficiency and should be evaluated for it.

Certain dog breeds, notably the Giant Schnauzer, Border Collie, and Beagle, carry a genetic predisposition for cobalamin malabsorption. This hereditary condition impedes the ileum (the final section of the small intestine) from effectively binding and transporting cobalamin into the bloodstream.

This means that despite consuming a balanced diet, affected dogs might still face a B12 deficiency. Symptoms, which typically emerge before six months of age, include failure to thrive, decreased appetite, lethargy, anemia, and GI issues like diarrhea.

Diagnosis of cobalamin malabsorption usually involves bloodwork to measure serum cobalamin levels and may include genetic tests, especially for informed breeding decisions. Managing this condition requires lifelong B12 supplementation (usually via injection) and regular veterinary monitoring. But with appropriate treatment, the prognosis is excellent.

“How do I know if my dog needs B12?” Signs of deficiency

B12 deficiency can manifest in several ways that affect your dog’s overall well-being:

  • Fatigue and lethargy: Reduced energy conversion means less pep in their step.
  • Loss of appetite and weight loss: A reduced appetite can be a telltale sign, potentially leading to weight loss.
  • Anemia: This condition results in pale gums and a decrease in red blood cell count. The less efficient oxygen transport can also cause fatigue and weakness.
  • Neurological symptoms: From tremors to uncoordinated movements or mental dullness, these can be distressing not just for our pets, but for us as their caregivers.
  • Gastrointestinal symptoms: Dogs might also experience diarrhea, nausea, or vomiting.
  • Dull, brittle fur coat: Changes to skin and fur coat can be a subtle sign that something’s amiss.

If you’re concerned that your dog may be deficient in B12, or if your dog is suffering from chronic gastrointestinal symptoms, it’s best to see your veterinarian for a physical exam. They may recommend a simple blood test to check your dog’s cobalamin levels, or a full workup to rule out other potential causes.

How do I add B12 to my dog’s diet?

Healthy dogs who are eating a complete and balanced diet approved by WSAVA and AAFCO should not need additional B12.

It’s also important to note that dogs with severe deficiencies or malabsorption issues may respond better to injectable B12 than an oral supplement. Injections are usually administered subcutaneously (under the skin), once a month, in your vet’s office.

Any supplementation should be discussed with your veterinarian. They’ll be able to determine the correct dosage and method of supplementation for your dog and let you know when your pup’s B12 levels should be rechecked.

Dietary Adjustments

Looking to ensure your dog gets adequate B12 from their diet? What is the best source of B12 for dogs? Here are some dog-friendly foods containing B12:

  • Meat and poultry: Ensure your dog's diet includes good sources of animal protein like beef, chicken, turkey, and lamb. Organ meats, especially liver and kidney, are particularly high in B12. Feeding raw meat is not recommended due to risk of parasites and bacterial contamination.
  • Fish: Sardines, salmon, and other fish are excellent sources of B12. (They’re also great sources of omega-3 fatty acids.)
  • Dairy and eggs: A small amount of scrambled eggs, cottage cheese, or yogurt can be given as an occasional treat, but too much dairy may cause gastrointestinal upset.
  • Fortified dog food: Some commercially available pet foods, especially those for senior dogs or those with specific health conditions, are fortified with extra vitamins, including B12.

If you do choose to add home-cooked food to your dog’s diet, be sure you’re using it as an occasional treat that doesn’t exceed 10% of their daily calories. This will help your dog’s diet remains complete and balanced.

Market with Meat, poultry, fish, and eggs

B12 Supplements

When indicated by your veterinarian, you may give your dog B12 supplements in either capsule, tablet, liquid, or injection form:

  • Oral supplements: Cyanocobalamin is often chosen for supplementation as it is widely available and inexpensive. Be sure to choose tablets or capsules that are formulated for dogs, as human supplements might contain levels or additional ingredients not suitable for canine consumption.
  • Liquid supplements: B12 is also available in liquid form, which can be added to your dog's food.
  • Injections: For dogs with severe deficiencies or malabsorption issues, veterinarians often recommend B12 injections, which are given under the skin for more direct delivery.


  • Digestive enzyme supplements: If your dog’s B12 deficiency is due to a digestive issue like EPI (see above section, “What can cause B12 deficiency in dogs?”), then adding a digestive enzyme supplement can help them break down food better and may improve the absorption of B12 and other nutrients.
  • Probiotics: Supporting gut health can indirectly benefit B12 absorption. Probiotics help maintain a healthy gut flora balance, ensuring optimal nutrient absorption.
Dog laying on the bed looking happy getting pets from human

Side effects of B12 supplementation

Vitamin B12 is a water-soluble vitamin, which means excess amounts are excreted through the urine. This makes B12 supplementation extremely safe, with a low risk of toxicity.

However, as with any supplement or treatment, there's potential for side effects, especially when B12 is given in very high doses.

Though extremely rare, some dogs might show an allergic reaction to a B12 supplement, especially if it contains additional ingredients. Symptoms could include itching, hives, difficulty breathing, or swelling of the face/lips/tongue. If you encounter these symptoms, take your dog to the emergency vet right away.

Questions? Leave a comment below! ⬇️

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