Vitamin B12 is a water-soluble vitamin.
Adults need approximately 0.0015 mg a day.
If you eat meat, fish or dairy foods then you should be able to get enough vitamin B12 from your diet.
However, because vitamin B12 isn't found in vegetable foods (such as fruit, vegetables and grains), vegans might not get enough of this vitamin and become deficient.
What does it do?
Vitamin B12 has a number of important functions. For example it:
helps make red blood cells and keeps the nervous system healthy
helps release energy from the food we eat
is needed to process folic acid
What happens if I take too much?
There isn't enough evidence to know what the effects might be of taking high doses of vitamin B12 supplements each day.
What is FSA advice?
You should be able to get all the vitamin B12 you need by eating a varied and balanced diet. But if you decide to take vitamin B12 supplements it's a good idea not to take too much because this might be harmful.
Taking 2 mg or less of vitamin B12 supplements a day is unlikely to cause any harm.