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Vitamin B-12 (Cyanocobalamin) (By mouth)

Supplies your body with vitamin B12. You might need a vitamin B12 supplement if your body has trouble using the vitamin B12 in the food you eat. You also might need vitamin B12 if you are a vegetarian, if you have had part of your stomach removed, or for other reasons. Prevents pernicious anemia, a blood problem caused by a lack of vitamin B12. Cyanocobalamin is another name for vitamin B12.

What works?

Learn more about the effects of these drugs. The most reliable research is summed up for you in our featured article.

Brand names include
B-12-SL, Good Neighbor Pharmacy Vitamin B12, Leader Natural Vitamin B12, Mason Natural B-12, Nature's Blend B12, Optimum Vitamin B-12, PharmAssure Vitamin B-12, Rite Aid Vitamin B-12, Sundown Naturals B12, Twelve Resin-K, Vitamist B12-500
Drug classes About this
Nutritive Agent, Vitamin B Combination

What works? Research summarized

Evidence reviews

Systematic review with dose-response meta-analyses between vitamin B-12 intake and European Micronutrient Recommendations Aligned's prioritized biomarkers of vitamin B-12 including randomized controlled trials and observational studies in adults and elderly persons.

BACKGROUND: Many randomized controlled trials (RCTs) and observational studies have provided information on the association between vitamin B-12 intake and biomarkers. The use of these data to estimate dose-response relations provides a useful means to summarize the body of evidence.

Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency

Vitamin B12 deficiency can cause anaemia and neurological complications. Vitamin B12 is rarely prescribed in the oral form in most countries. Two randomised controlled studies were included in this review. The trials recruited a total of 108 participants and followed up 93 of these from 90 days to four months. The evidence derived from these limited studies suggests that high oral doses of B12 (1000 mcg and 2000 mcg) could be as effective as intramuscular administration in achieving haematological and neurological responses.

No evidence that folic acid with or without vitamin B12 improves cognitive function of unselected elderly people with or without dementia. Long‐term supplementation may benefit cognitive function of healthy older people with high homocysteine levels

In the economically developed world, folate deficiency is one of the commonest vitamin deficiencies. Several reports suggest a higher prevalence of various psychiatric disorders in elderly people with folate deficiency. There is interest in whether dietary supplements of folic acid (an artificial chemical analogue of naturally occurring folates) can improve cognitive function of people at risk of cognitive decline associated with ageing or dementia, whether by affecting homocysteine metabolism or through other mechanisms. Eight trials met the criteria for inclusion. It was not possible to pool the data because the trials studied different populations, tested folic acid in different doses, and used different outcome measures. There were two trials of folic acid in conjunction with B12. The analysis showed significant benefit of folic acid over placebo in some measures of cognition in a long‐term trial recruiting elderly people with high homocysteine levels from a general population. In one pilot trial, 1 mg/day of folic acid was associated with significant improvement in behavioural response to cholinesterase inhibitors in people with Alzheimer's disease.

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Summaries for consumers

Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency

Vitamin B12 deficiency can cause anaemia and neurological complications. Vitamin B12 is rarely prescribed in the oral form in most countries. Two randomised controlled studies were included in this review. The trials recruited a total of 108 participants and followed up 93 of these from 90 days to four months. The evidence derived from these limited studies suggests that high oral doses of B12 (1000 mcg and 2000 mcg) could be as effective as intramuscular administration in achieving haematological and neurological responses.

No evidence that folic acid with or without vitamin B12 improves cognitive function of unselected elderly people with or without dementia. Long‐term supplementation may benefit cognitive function of healthy older people with high homocysteine levels

In the economically developed world, folate deficiency is one of the commonest vitamin deficiencies. Several reports suggest a higher prevalence of various psychiatric disorders in elderly people with folate deficiency. There is interest in whether dietary supplements of folic acid (an artificial chemical analogue of naturally occurring folates) can improve cognitive function of people at risk of cognitive decline associated with ageing or dementia, whether by affecting homocysteine metabolism or through other mechanisms. Eight trials met the criteria for inclusion. It was not possible to pool the data because the trials studied different populations, tested folic acid in different doses, and used different outcome measures. There were two trials of folic acid in conjunction with B12. The analysis showed significant benefit of folic acid over placebo in some measures of cognition in a long‐term trial recruiting elderly people with high homocysteine levels from a general population. In one pilot trial, 1 mg/day of folic acid was associated with significant improvement in behavioural response to cholinesterase inhibitors in people with Alzheimer's disease.

Interventions for lowering plasma homocysteine levels in dialysis patients

People with advanced kidney disease frequently develop heart disease, which is the most common cause of deaths in these people. An increased level of the amino acid (homocysteine) in the blood is a risk factor for heart disease in people with advanced kidney disease. Therapies that reduce homocysteine levels (e.g. folic acid, vitamins B6 and B12) are often used, but the benefits and harms of their use are unclear. We aimed to assess the benefits and harms of homocysteine‐lowering therapies in people with advanced kidney disease who were on dialysis.

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