Vitamin B12
Cobalamin
Vitamins. Modern nutrition.
Also called Cyanocobalamin, Methylcobalamin, Hydroxocobalamin, Vitamin B-12
Pinyin: wéishēngsù B12
Spanish: Cobalamina
A B vitamin the body needs for healthy nerves and red blood cells. It comes almost only from animal foods and fortified products.
Did you know? Vitamin B12 is the only vitamin built around a metal atom. Its center holds cobalt, which is why it is called cobalamin.
What it may help, and how strong the proof is
- Anemia & blood building. B12 deficiency causes pernicious anemia and other anemias with large red blood cells. B12 shots or pills correct this in people who are low. Extra B12 does not raise blood levels in people who already have enough.Strong proof
- Nerve health. Low B12 can cause numbness, tingling, balance problems and memory trouble. Treatment helps the nerves, but long-standing damage may not fully heal.Good proof
- Energy & tiredness. B12 is sold for energy. In people who are not low in B12, extra B12 has not been shown to add energy.Not supported
Parts of the body
Traditional use
Traditional diets with meat, fish, eggs and dairy supplied enough B12. In the 1920s, doctors found that eating large amounts of liver helped people with pernicious anemia, long before B12 was identified.
How it is classified
How people take it
Adults need 2.4 mcg a day (RDA). Pregnant women need 2.6 mcg a day, and breastfeeding women need 2.8 mcg a day. No upper limit has been set, because the body absorbs only a small share of very large oral doses and no harm from high doses is known. Pill doses of 25 to 1,000 mcg are common.
Food, tablet and capsule.
Where to get it
Good sources are clams (very rich), beef and chicken liver, trout, salmon, tuna, beef, eggs, milk, cheese and yogurt. Fortified breakfast cereals and nutritional yeast also supply B12. Pills come as cyanocobalamin (the most common form), methylcobalamin, or sublingual tablets that dissolve under the tongue.
Be careful
B12 is very safe, even at high doses. Shots rarely cause itching or allergic reactions. People who are vegan, older, or taking acid-lowering drugs or metformin should have their B12 level checked.
Avoid if: allergy to B12 (rare).
Mixing with other things
- Works well together
B6, B12 and folate all help keep blood levels of homocysteine in check.
- Works well together
Often sold together in hair and nail blends. There is no proof that they work better as a pair.
- Works well together
Iron, B12 and folate are all needed to make healthy red blood cells.
- Use cautionDiabetes medicine (metformin, insulin, glipizide, Ozempic)
Metformin lowers B12 absorption over time, so long-term users should have B12 levels checked.
- Worth knowingAlcohol (beer, wine, spirits)
Heavy drinking can lower B12 absorption and storage.
- Worth knowing
High folate can hide B12 deficiency symptoms, so both should be checked when needed.
Adds up with others that may lower blood sugar: , , , , , , , , , , , , , and 39 more.
The honest take
B12 is essential, and deficiency is common in older adults, vegans, and people on acid-lowering drugs or metformin. Shots and pills both work for true deficiency. Extra B12 for energy, mood or hair is mostly hype when levels are normal.