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Vitamin B12 is an essential vitamin found in foods such as meat, fish, and dairy. It can also be made in a lab and is often taken with other B vitamins.
Vitamin B12 is required for the function and development of many parts of the body, including the brain, nerves, and blood cells. Methylcobalamin is the active form of vitamin B12. Cyanocobalamin, which must be processed by the body into the active form, is the most common type used in supplements.
People commonly use vitamin B12 for vitamin B12 deficiency, cyanide poisoning, and high levels of homocysteine in the blood. It is also used for canker sores, cataracts, Alzheimer disease, osteoporosis, fatigue, and many other conditions, but there is no good scientific evidence to support most of these other uses.
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- Imerslund-Grasbeck disease. Intramuscular vitamin B12 is effective for patients with this condition.
Login for details - Vitamin B12 deficiency. Administering vitamin B12 orally, intramuscularly, or intranasally is effective for preventing and treating vitamin B12 deficiency.
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- Cyanide poisoning. Intravenous hydroxocobalamin (Cyanokit) is likely effective as an antidote for patients with suspected or known cyanide toxicity due to inhalation, ingestion, or skin exposure.
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- Canker sores. Sublingual or topical vitamin B12 seems to reduce canker sore symptoms.
Login for details - Hyperhomocysteinemia. Oral vitamin B12 in combination with folic acid, and sometimes with vitamin B6, reduces homocysteine levels.
Login for details - Postherpetic neuralgia. Subcutaneous injections of vitamin B12 seem to reduce postherpetic neuralgia symptoms.
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- Age-related cognitive decline. Oral vitamin B12 does not seem to improve cognitive function in older adults when used alone or in combination with other B vitamins.
Login for details - Alzheimer disease. Oral vitamin B12, when used in combination with other B vitamins, does not seem to improve cognitive function in patients with Alzheimer disease.
Login for details - Cataracts. Oral vitamin B12 does not seem to reduce cataract development.
Login for details - Circadian rhythm sleep disorders. Oral vitamin B12 does not seem to improve sleep disorders.
Login for details - Cognitive impairment. Oral vitamin B12 does not seem to be beneficial for older adults with cognitive impairment.
Login for details - Fall prevention. Oral vitamin B12 does not seem to reduce the risk of falls.
Login for details - Osteoporosis. Oral vitamin B12 does not seem to reduce the risk of osteoporotic fractures.
Login for details - Physical performance. Oral vitamin B12 does not seem to improve physical performance in older adults.
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- Age-related macular degeneration (AMD). Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease). It is unclear if high-dose intramuscular vitamin B12 improves the prognosis of ALS.
Login for details - Angioplasty. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Anxiety. Login for details
- Asthma. Login for details
- Atherosclerosis. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Atopic dermatitis (eczema). It is unclear if topical vitamin B12 reduces the severity of eczema.
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- Cancer. It is unclear if oral vitamin B12 reduces overall cancer risk when used in combination with other B vitamins.
Login for details - Cardiovascular disease (CVD). Oral vitamin B12, taken along with other B vitamins, does not seem to improve secondary prevention of death or myocardial infarction in patients with CVD. However, it might slightly reduce the risk of stroke.
Login for details - Cervical cancer. It is unclear if oral vitamin B12 reduces cervical cancer risk.
Login for details - Chemotherapy-induced peripheral neuropathy. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Child development. It is unclear if oral vitamin B12 is beneficial for child development.
Login for details - Chronic obstructive pulmonary disease (COPD). It is unclear if oral vitamin B12 reduces the risk of COPD.
Login for details - Cognitive function. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Colorectal cancer. It is unclear if oral vitamin B12 reduces colorectal cancer risk.
Login for details - Coronavirus disease 2019 (COVID-19). It is unclear if oral vitamin B12 is beneficial for patients with COVID-19.
Login for details - Dementia. It is unclear if oral vitamin B12 reduces the risk of developing dementia.
Login for details - Depression. It is unclear if oral vitamin B12 is beneficial for reducing depression risk.
Login for details - Diabetes. It is unclear if oral vitamin B12 improves glycemic indices or prevents loss of skeletal muscle in patients with diabetes.
Login for details - Diabetic neuropathy. Small clinical studies suggest that oral vitamin B12 may modestly improve pain in patients with diabetic neuropathy.
Login for details - Diarrhea. It is unclear if oral vitamin B12 is beneficial for reducing diarrhea in children.
Login for details - Fatigue. It is unclear if intramuscular vitamin B12 is beneficial for improving well-being in those with fatigue or tiredness.
Login for details - Hearing loss. Oral vitamin B12 has only been evaluated in combination with adenosine triphosphate; its effect when used alone is unclear.
Login for details - Hepatitis C. It is unclear if intramuscular vitamin B12 is beneficial for sustaining viral response in patients with chronic hepatitis C infection.
Login for details - Hypertriglyceridemia. It is unclear if oral vitamin B12 is beneficial for reducing triglyceride levels.
Login for details - Infant development. It is unclear if taking oral vitamin B12 during pregnancy is beneficial for improving infant development. Giving oral vitamin B12 to infants does not seem to be beneficial.
Login for details - Inflammatory bowel disease (IBD). Login for details
- Lung cancer. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Male infertility. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Multiple sclerosis (MS). Login for details
- Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral vitamin B12 is beneficial for NAFLD.
Login for details - Pancreatic cancer. It is unclear if oral vitamin B12 is beneficial for reducing the risk of pancreatic cancer.
Login for details - Periodontitis. Login for details
- Peripheral neuropathy. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Psoriasis. Topical vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Respiratory tract infections. A small study suggests that oral vitamin B12 does not reduce the rate of respiratory tract infections in children.
Login for details - Schizophrenia. Oral vitamin B12 has only been evaluated in combination with other ingredients; its effect when used alone is unclear.
Login for details - Sickle cell disease. Oral vitamin B12 has only been evaluated in combination with other B vitamins; its effect when used alone is unclear.
Login for details - Stroke. It is unclear if oral vitamin B12, either alone or with other B vitamins, is beneficial for stroke prevention.
Login for details - Tinnitus. It is unclear if intramuscular vitamin B12 is beneficial in patients with tinnitus.
Login for details - Venous thromboembolism (VTE). It is unclear if oral vitamin B12 is beneficial for preventing VTE.
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When taken by mouth: Vitamin B12 is likely safe for most people. Vitamin B12 is considered safe even in large doses.
When applied to the skin: Vitamin B12 is likely safe for most people when used appropriately.
When sprayed into the nose: Vitamin B12 is likely safe for most people. Vitamin B12 is considered safe even in large doses.
Special Precautions & Warnings:
Pregnancy and breast-feeding: Vitamin B12 is likely safe when taken by mouth during pregnancy or breast-feeding in the amounts recommended. The recommended amount for pregnancy is 2.6 mcg per day. Those breast-feeding should take 2.8 mcg per day. 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.
It is not known if Vitamin B12 interacts with any medicines. Before taking Vitamin B12, talk with your healthcare professional if you take any medications.
Folic acid: Folic acid, particularly in large doses, can cover up vitamin B12 deficiency, and cause serious health effects. Be sure that your healthcare provider checks your vitamin B12 levels before you start taking folic acid.
Potassium: Potassium supplements can reduce absorption of vitamin B12 in some people and might contribute to vitamin B12 deficiency.
Vitamin C: Vitamin C supplements can destroy dietary vitamin B12. It isn't known whether this interaction is important, but to stay on the safe side, take vitamin C supplements at least 2 hours after meals.
Heavy drinking for at least two weeks can decrease vitamin B12 absorption from the stomach.
Vitamin B12 is an essential nutrient. Fish, shellfish, meat, eggs, and dairy products are good sources of vitamin B12. The amount that should be consumed on a daily basis is called the recommended dietary allowance (RDA). The RDA is 2.4 mcg daily for people 18 years and older. While pregnant, the RDA is 2.6 mcg daily. While breastfeeding, the RDA is 2.8 mcg daily. In children, the RDA depends on age.
People over 50 years of age are advised to eat foods fortified with vitamin B12 or to take a vitamin B12 supplement. 25-100 mcg daily has been taken by mouth to maintain vitamin B12 levels in older adults. Speak with a healthcare provider to find out what dose might be best for a specific condition.
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