Dimethylglycine (DMG) is a derivative of the amino acid glycine found in beans and liver. It can be formed from trimethylglycine upon the loss of one of its methyl groups. It is also a byproduct of the metabolism of choline. When DMG was first discovered, it was referred to as vitamin B16, but unlike true B vitamins, deficiency of DMG in the diet does not lead to any ill effects.

Trimethylglycine (TMG) is related to choline (trimethylaminoethanol), with the difference that the terminal carboxylic acid group of trimethylglycine has been reduced to a hydroxyl group in choline. The product of demethylation of TMG is dimethylglycine.