Vitamins

Vitamins are a group of organic compounds used in biochemical pathways. Many are components of coenzymes in particular metabolic reactions. Vitamins are generally not synthesized by the human body and hence must be acquired through the diet. 
Vitamer is the name given to the different forms of a particular vitamin and are numbered with a subscript style to differentiate them, e.g. vitamin K exists as both K1 and K2 vitamers.

In radiology, there are some imaging manifestations of disease due to abnormally high (hypervitaminosis) and low (hypovitaminosis) levels of particular vitamins.

Vitamins can be classified into fat-soluble and water-soluble molecules.

The B vitamins were historically grouped together as the vitamin B complex. However their chemical structures are unrelated. The B-complex vitamins are numbered and by scientific convention the number is always subscripted.

Fat-soluble vitamins

• vitamin A
• vitamin D
• vitamin E
• vitamin K

Water-soluble vitamins

• B vitamins
  • vitamin B1
  • vitamin B2
  • vitamin B3
  • vitamin B5
  • vitamin B6
  • vitamin B7
  • vitamin B9
  • vitamin B12
• vitamin C

NB Vitamins B4, B8, B10, B11, and B13 - B17 have been reclassified and no longer meet the biochemical definition of vitamins or are only vitamins in non-human species.