L-carnitine is a compound of the essential amino acids L-lysine and L-methionine. It is required for syntheses that carry fatty acids and for channelling fatty acids for mitochondrial energy generation.

A portion of the requirement can be synthesized in the body if the required amino acids and cofactors are sufficiently available. The residual amount must be taken up through the daily diet. Only red meat can supply sufficient amounts, several fish and mushrooms contain small amounts.

People suffering from diseases like a heart or kidney insufficiency cannot cover their increased requirement for L-carnitine through synthesis and their diet. Taking L-carnitine improves the use of fats and the energy supply so that symptoms of an energy deficiency can be alleviated. This contributes to stabilizing these diseases.