The necessary amount of vitamin is usually expressed in terms of RDA, which is the Recommended Daily Allowance of a vitamin. These are the values used for nutritional labelling of food products.

However, individual needs may vary. For example, higher levels of vitamins are recommended for people who have certain diseases. Medicine can also suppress the working of a vitamin. Certain groups need higher amounts of particular vitamins. For example children (vitamin D), pregnant women (folic acid), older people (vitamin D), smokers (vitamin C), people who consume a lot of alcohol (thiamine) or vegetarians and vegans (vitamin B12) need higher amounts of certain vitamins.

As RDA values may vary between countries and are often updated, no data are given here. Please refer to your national nutrition institute for the data valid in your country.