L-carnitine / acetyl-L-carnitine

Also known as carnitine, ALCAR, acetyl l carnitine, l-carnitine tartrate.

Last reviewed October 9, 2026 · Jump to references

What is L-carnitine / acetyl-L-carnitine?

In plain words

L-carnitine is a substance the body makes from amino acids, the building blocks of protein; acetyl-L-carnitine is a closely related form. The body uses carnitine to help turn fat into energy, while the acetyl form also helps handle small chemical units used in energy production. Researchers study these compounds for carnitine deficiency, fatigue, nerve problems, and memory. Evidence for benefits beyond treating deficiency is mixed and depends on the condition studied.

Technical definition

L-carnitine is an amino-acid-derived quaternary ammonium compound synthesized from lysine and methionine; acetyl-L-carnitine (ALCAR) is its acetylated derivative. L-carnitine is transported into cells by OCTN2 and participates in the carnitine shuttle, enabling long-chain fatty acids to enter mitochondria for oxidation, while ALCAR participates in acetyl-group metabolism and can cross the blood–brain barrier. In the United States, both are marketed as dietary supplements, while prescription levocarnitine is approved for specific carnitine-deficiency conditions; supplement products are not FDA-approved treatments.

Educational information only. This page does not provide medical advice or determine whether a supplement is appropriate for you. Review supplements with a qualified healthcare professional, especially if you take medication, are pregnant, have surgery scheduled, or have a chronic medical condition.

Evidence by use

Each use is rated on its own. There is no single overall effectiveness score.