Natural Health Products

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Vitamin B12

General Information

Cyanocobalamin, or vitamin B12, is a water-soluble vitamin that cannot be stored in the body. Excess vitamin B12 is passed out of the body through the urine. Vitamin B12 is available as a supplement, and it can be found in animal food sources such as meat, fish, beef liver, clams, eggs, and diary products. Vitamin B12 is often used in combination with other B vitamins in a vitamin B complex formulation.

Common Name(s)
vitamin B12, cyanocobalamin
Scientific Name(s)
vitamin B12
How is this product usually used?

Vitamin B12 is usually taken by mouth. It is available in different forms, including chewable tablets and gummies, capsules, tablets, powders, strips, drops, and liquids. Vitamin B12 is also available in an injectable form to be given subcutaneously (into skin fat), intramuscularly (into muscles), or intravenously (into veins).

Table 1 lists the usual dose range and the recommended dietary allowance (RDA) for vitamin B12 for different age groups. People with vitamin B12 deficiency might need doses at or above the RDA.

Table 1. Usual daily dose range and RDA for vitamin B12 for different age groups

Age group

Vitamin B12 (µg/day)




Usual dose


1–3 years



4–8 years




9–13 years



14–18 years




≥19 years




14–50 years




14–50 years



Injectables are usually dosed at 250–1000 µg monthly.

Your health care provider may have recommended using this product in other ways. Contact a health care provider if you have questions.

What is this product used for?

Vitamin B12 is important in maintaining overall good health. It helps the body to form red blood cells and to metabolize carbohydrates, fats, and proteins. It is important for the proper function and development of the brain and nerves.

At doses at or above the RDA, vitamin B12 supplementation is highly effective for preventing and treating vitamin B12 deficiency and associated diseases such as pernicious anemia (a type of anemia due to vitamin B12 deficiency). Some people may have low vitamin B12 levels because of absorption problems or inadequate amounts in their diet (for example, vegetarians are at risk since vitamin B12 is available only from animal food sources). Vitamin B12 supplementation in these cases can help prevent vitamin B12 deficiency.

Vitamin B12 has also been studied to prevent heart diseases and to treat Alzheimer’s disease, memory loss, male infertility, diabetes, mental disorders, inflammatory bowel disease, asthma, fatigue, and high cholesterol. However, there is not enough reliable evidence for these uses; additional studies are required to confirm the benefits of vitamin B12 in these conditions.

Vitamin B12 has also been studied together with folic acid and vitamin B6 for prevention of recurrent strokes and breast cancer. However, research has shown that this combination of supplements did not lower the risk of stroke or breast cancer.

Your health care provider may have recommended this product for other conditions. Contact a health care provider if you have questions.

What else should I be aware of?

Vitamin B12 is generally well tolerated by most people if taken in recommended amounts. Side effects may include mild diarrhea, itching, blood clots, urine discoloration, and allergic reactions.

People with Leber’s disease (a genetic eye disease) or those who are allergic or sensitive to cobalt or cobalamin should consult their health care provider before taking vitamin B12 supplements.

People with anemia need to talk to their health care provider about what treatment is right for them before starting any type of vitamin supplementation. Taking vitamin B12 supplements before a proper diagnosis from the doctor may make it harder for your doctor to diagnose the type of anemia you have.

Vitamin B12 is safe for pregnant or breast-feeding women when taken by mouth in recommended amounts.

Vitamin B12 from food sources can interact with certain medications, including proton pump inhibitors (e.g., omeprazole, pantoprazole), H2 blockers (e.g., famotidine, ranitidine), and metformin. These can affect the absorption of dietary B12 into the body, though this does not appear to be a problem with supplements. Heavy drinking for more than 2 weeks can also decrease vitamin B12 absorption.

Avoid taking the combination of vitamin B12 and chloramphenicol (an antibiotic) since chloramphenicol can destroy the newly produced blood cells that vitamin B12 helped to make.

Vitamin C and potassium supplements can decrease the effects of vitamin B12. It is not known whether this interaction is clinically significant or not. You can avoid this by separating the vitamins and taking them at least 2 hours apart. Consult your health care provider for more information on drug interactions.

Before taking any new medications, including natural health products, speak to your physician, pharmacist, or other health care provider. Tell your health care provider about any natural health products you may be taking.

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