- What other names is Vitamin B12 known by?
- What is Vitamin B12?
- How does Vitamin B12 work?
- Are there safety concerns?
- Are there any interactions with medications?
- Dosing considerations for Vitamin B12.
Vitamin B12 is taken by mouth to treat and prevent vitamin B12 deficiency, a condition in which vitamin B12 levels in the blood are too low.
Vitamin B12 is also taken by mouth for memory loss, Alzheimer's disease, to slow aging, and to boost mood, energy, concentration, mental function, and the immune system. It is also used for heart disease, clogged arteries and decreasing the risk of re-clogging arteries after surgery, high triglyceride levels, lowering high homocysteine levels (which may contribute to heart disease), male infertility, diabetes, diabetic nerve damage, nerve damage in the hands or feet, sleep disorders, depression, mental disorders, schizophrenia, weak bones (osteoporosis), swollen tendons, AIDS, inflammatory bowel disease, diarrhea, asthma, allergies, a skin disease called vitiligo, and skin infections.
Some people use vitamin B12 by mouth for amyotrophic lateral sclerosis (Lou Gehrig's disease), multiple sclerosis, preventing the eye disease age-related macular degeneration (AMD), a condition in which the body products too much thyroid hormone, Lyme disease and gum disease. It is also used by mouth for respiratory tract infections, maintaining fertility, ringing in the ears, bleeding, liver and kidney disease, canker sores, preventing fractures, preventing stroke, preventing blood clots, and for protection against the poisons and allergens in tobacco smoke. It is also taken by mouth to prevent cancer, including breast cancer, cervical cancer, colorectal cancer, and lung cancer.
Vitamin B12 is applied to the skin either alone or in combination with avocado oil for psoriasis and eczema. Also, a vitamin B12 nasal gel is applied for pernicious anemia and preventing and treating vitamin B12 deficiency.
Vitamin B12 is injected into the body for pernicious anemia, to prevent and treat vitamin B12 deficiency, and to prevent and treat a nervous system disorder called myelopathy, which can occur in people who are vitamin B12 deficient. It is also used for tremors, to treat Imerslund-Grasbeck disease, cyanide poisoning, nerve damage caused by shingles, diabetic nerve damage, tiredness or fatigue, chronic fatigue syndrome, hepatitis C, a condition in which the body products too much thyroid hormone, bleeding, cancer, psoriasis, and liver and kidney disease. It is also injected in the body to prevent arteries from re-clogging after surgery.
- Inherited Vitamin B12 deficiency (Imerslund-Grasbeck disease). Injecting vitamin B12 as a shot for 10 days followed by monthly injections for the remainder of life is effective for treating people with an inherited disease that results in poor absorption of vitamin B12.
- Vitamin B12 deficiency. Vitamin B12 can treat and prevent vitamin B12 deficiency. It can be taken by mouth, as a shot, or through the nose. The shot works best in people with severe vitamin B12 deficiency or associated nerve damage.
Likely Effective for...
- Cyanide poisoning. Administering hydroxocobalamin (Cyanokit), a natural form of vitamin B12, as a shot for a total dose of up to 10 grams is likely an effective treatment for cyanide poisoning. Treatment of cyanide poising with hydroxocobalamin (Cyanokit) has been approved by the U.S. Food and Drug Administration (FDA).
- High level of homocysteine in the blood (Hyperhomocysteinemia). Taking vitamin B12 by mouth, along with folic acid and sometimes pyridoxine (vitamin B6), can lower blood levels of homocysteine.
Possibly Effective for...
- An eye disease called age-related macular degeneration (AMD). Some research shows that taking vitamin B12 with other B vitamins, including folic acid and vitamin B6, might help prevent an eye disease called age-related macular degeneration. But the effects of vitamin B12 alone on AMD are not clear.
- Nerve damage from shingles. Some research shows that injecting vitamin B12 in the form of methylcobalamin under the skin six times weekly for 4 weeks reduces pain more than taking vitamin B12 by mouth or injecting lidocaine under the skin in people with nerve damage from shingles. Other research shows that it reduces pain and the need for painkillers. Adding thiamine to the treatment also seems to reduce itching.
Possibly Ineffective for...
- Cancer. Research suggests that taking vitamin B12 in the form of cyanocobalamin along with folate and vitamin B6, with or without eicosapentanoic acid (EPA) plus docosahexaenoic acid (DHA) does not reduce the risk of developing cancer in older adults with heart disease. Some research actually suggests that taking vitamin B12 and folic acid daily for 2 years might increase the risk of cancer in older people.
- Sleep disorders. Taking vitamin B12 by mouth does not seem to help people with sleep disorders.
- Mental function. Taking vitamin B12, alone or in combination with folic acid and vitamin B6, does not seem to improve memory, language, or the ability to organize and plan in elderly people.
- Fractures. Taking vitamin B12 and folic acid, with or without vitamin B6 daily for 2-3 years does not seem to reduce the risk of fractures in older people with osteoporosis.
- Stroke. Research suggests that people who consume more vitamin B12 in their diet or those who take vitamin B12 supplements do not have a reduced risk of stroke or stroke reoccurrence.
Insufficient Evidence to Rate Effectiveness for...
- Alzheimer's disease. Some early research suggests that higher vitamin B12 intake does not prevent Alzheimer's disease. However, other early research shows that taking vitamin B12 along with vitamin B6 and folic acid for 2 years might slow brain changes that are linked with mental decline and Alzheimer's disease.
- Preventing re-blockage of blood vessels after heart artery dilation (balloon angioplasty). Research is inconsistent about the benefits of taking folic acid plus vitamin B6 and vitamin B12 following angioplasty. Some research suggests that it might decrease the risk of re-blockage of the blood vessels after balloon angioplasty. However, it does not seem to benefit people who had a tube (coronary stent) placed in the arteries.
- Clogged arteries. Early research shows that taking vitamin B12, aged garlic extract, folic acid, vitamin B6, and L-arginine daily for 12 months slows the progression of clogged arteries and improves blood vessel function in people at risk for clogged arteries. The effect of vitamin B12 alone is not clear.
- Eczema (atopic dermatitis). Early research shows that applying a vitamin B12 cream (Regividerm) to the affected area twice daily helps treat eczema.
- Breast cancer. There is no evidence that dietary vitamin B12 alone reduces the risk of breast cancer. However, vitamin B12 may reduce the risk of breast cancer when taken with folate, vitamin B6, and methionine.
- Canker sores. Early research shows that taking vitamin B12 1000 mcg under the tongue (sublingually) might help reduce the number of canker sore outbreaks, the duration of outbreaks, and pain caused by the canker sores.
- Cervical cancer. Early research suggests that different forms of vitamin B12 taken together with a thiamine derivative (benfotiamine) and vitamin B6 might improve some symptoms of nerve pain associated with diabetes.
- Colon and rectal cancer. Some population research suggests that people who consume more vitamin B12 in their diet have a lower risk of developing colon or rectal cancer. But early research shows that taking vitamin B12 with folic acid and vitamin B6 daily for up to 7.3 years does not reduce the risk of developing colorectal cancer in women.
- Nerve damage caused by diabetes. Early research suggests that different forms of vitamin B12 taken together with a thiamine derivative (benfotiamine) and vitamin B6 might improve some symptoms of nerve damage associated with diabetes. Taking a specific medical food containing specific forms of vitamin B12, folic acid, and vitamin B6 also seems to have beneficial effects. Taking vitamin B12 alone by mouth or injected into the vein might help reduce pain but does not improve motor or sensory nerve function in people with nerve damage caused by diabetes.
- Diarrhea. Early research suggests that taking twice the recommended daily allowance of vitamin B12, with or without folic acid, does not reduce the risk of diarrhea in children.
- Fatigue. There is some evidence that receiving shots containing 5 mg of vitamin B12 in the form of hydroxocobalamin twice weekly might improve general well-being and happiness in people with fatigue.
- Hepatitis C. Early research shows that giving an injection of vitamin B12 in the form of cyanocobalamin every 4 weeks along with standard care can improve hepatitis C treatment.
- High triglyceride levels. Some evidence suggest that taking 7.5 mcg of vitamin B12 together with 5 grams of fish oil might be more effective then fish oil alone when used daily to reduce total cholesterol and triglyceride levels.
- Lower respiratory tract infections. Early research suggests that taking twice the recommended daily allowance of vitamin B12, with or without folic acid, does not reduce the risk for lower respiratory tract infections in children.
- Lung cancer. Early evidence suggests that there is no relationship between levels of vitamin B12 in the blood and the risk of lung cancer.
- Nerve damage in the hands and feet (peripheral neuropathy). Early research shows that taking a specific product containing vitamin B12 (Keltican) daily for 60 days reduces pain by 44% and reduces the need for painkillers by over 75% in people with nerve damage in parts of the body such as the hands and feed.
- Psoriasis. Early research shows that a specific cream containing vitamin B12 and avocado oil (Regividerm, Regeneratio Pharma AG) reduces symptoms of psoriasis as effectively as standard care and causes less irritation.
- Schizophrenia. Early research shows that taking vitamin B12 with folic acid daily for 16 weeks can improve symptoms of schizophrenia related to abnormal emotions and behavior. But the treatment only seems to benefit some patients.
- Shaky-leg syndrome. There are some reports that one form of vitamin B12 (cyanocobalamin) can help reduce tremors due to shaky-leg syndrome.
- Blood clots in the veins. Population research suggests that having low levels of vitamin B12 might be linked to an increased risk for blood clots in the veins. But research evaluating the use of vitamin B12 to prevent blood clots in the veins is unclear.
- Chronic fatigue syndrome (CFS).
- Heart disease.
- Immune system problems.
- Lyme disease.
- Memory problems.
- Multiple sclerosis.
- Other conditions.
Quick GuideHeart Disease: Symptoms, Signs, and Causes
Mild itching has been reported in one person who used a specific avocado oil plus vitamin B12 cream for psoriasis.
Special Precautions & Warnings:Pregnancy and breast-feeding: Vitamin B12 is LIKELY SAFE for pregnant or breast-feeding women when taken by mouth in the amounts recommended. The recommended amount for pregnant women is 2.6 mcg per day. Breast-feeding women should take no more than 2.8 mcg per day. Don't take larger amounts. The safety of larger amounts is unknown.
Post-surgical stent placement: Avoid using a combination of vitamin B12, folate, and vitamin B6 after receiving a coronary stent. This combination may increase the risk of blood vessel narrowing.
Allergy or sensitivity to cobalt or cobalamin: Do not use vitamin B12 if you have this condition.
Leber's disease, a hereditary eye disease: Do not take vitamin B12 if you have this disease. It can seriously harm the optic nerve, which might lead to blindness.
Abnormal red blood cells (megaloblastic anemia): Megaloblastic anemia is sometimes corrected by treatment with vitamin B12. However, this can have very serious side effects. Don't attempt vitamin B12 therapy without close supervision by your healthcare provider.
High numbers of red blood cells (polycythemia vera): The treatment of vitamin B12 deficiency can unmask the symptoms of polycythemia vera.
Interaction Rating: Major Do not take this combination.
Vitamin B12 is important for producing new blood cells. Chloramphenicol might decrease new blood cells. Taking chloramphenicol for a long time might decrease the effects of vitamin B12 on new blood cells. But most people only take chloramphenicol for a short time, so this interaction isn't a big problem.
- The typical general supplemental dose of vitamin B12 is 1-25 mcg per day: The recommended dietary allowances (RDAs) of vitamin B12 are: 1.8 mcg; older children and adults, 2.4 mcg; pregnant women, 2.6 mcg; and breast-feeding women, 2.8 mcg. Because 10% to 30% of older people do not absorb food-bound vitamin B12 efficiently, those over 50 years should meet the RDA by eating foods fortified with B12 or by taking a vitamin B12 supplement. Supplementation of 25-100 mcg per day has been used to maintain vitamin B12 levels in older people.
- For vitamin B12 deficiency: Vitamin B12 doses of 300-10,000 mcg daily have been used. However, some evidence suggests that the most effective oral dose is between 647-1032 mcg daily.
- For high blood levels of homocysteine: Vitamin B12 doses of 400-500 mcg in combination with 0.54-5 mg of folic acid and 16.5 mg of pyridoxine has been used.
- For preventing age-related macular degeneration (AMD): A combination of 1 mg of vitamin B12, 2.5 mg of folic acid, and 50 mg of pyridoxine daily has been used for 7.3 years.
- For atopic dermatitis (eczema): A specific vitamin B12 0.07% cream (Regividerm) applied twice daily has been used.
- For psoriasis: A specific cream (Regividerm, Regeneratio Pharma AG, Wuppertal, Germany) containing avocado oil plus vitamin B12 0.7 mg/gram applied for 12 weeks twice daily has been used.
- For vitamin B12 deficiency: The usual dose is 30 mcg as an injection into the muscle or under the skin daily for 5-10 days. For maintenance therapy, 100-200 mcg once monthly is commonly used. Both cyanocobalamin and hydroxocobalamin forms are used. The usual dose for pernicious anemia-associated vitamin B12 deficiency is 100 mcg given as an injection into the muscle or under the skin once daily for 6-7 days. Then the dose may be given every other day for 7 doses followed by every 3-4 days for around 3 weeks. Then, 100 mcg should be injected every month for life. Another dosing recommendation for injectable vitamin B12 includes 1000 mcg daily for 7-10 days followed by 1000 mcg weekly for 1 month followed by 1000 mcg monthly for life.
- For a hereditary condition that causes vitamin B12 malabsorption (Imerslund-Grasbeck disease): Vitamin B12 in the form of hydroxocobalamin has been injected into the muscle at a dose of 1 mg daily for 10 days followed by once monthly for the remainder of the person's life.
- For cyanide poisoning:Hydroxocobalamin (Cyanokit) has been given intravenously (by IV) for a total dose of up to 10 grams.
- For vitamin B12 deficiency: Doses of 500 mcg of vitamin B12 have been injected into one nostril weekly.
- For nerve damage from shingles: As an injection under the skin, 1000 mcg of vitamin B12, with or without 100 mg of thiamine, has been given six times weekly for 4 weeks.
- The recommended dietary allowances (RDAs) of vitamin B12 are: Infants 0-6 months, 0.4 mcg; infants 7-12 months, 0.5 mcg; children 1-3 years, 0.9 mcg; children 4-8 years, 1.2 mcg; children 9-13 years, and 1.8 mcg; older children.
- For vitamin B12 deficiency: Injecting 0.2 mcg/kg of vitamin B12 into the muscle or under the skin once daily for 2 days, followed by a 1000 mcg injection daily for 2-7 days and another 100 mcg injection weekly for 4 weeks thereafter has been used. Additional injections of 100 mcg monthly may be needed depending on level of symptom improvement and cause of vitamin B12 deficiency.
Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Healthy Heart Resources
Last Editorial Review: 3/29/2011