L carnitine is an amino acid that is produced in your body that helps the body turn fat into energy. Carnitine is found in nearly all cells of the body and researchers have The glycemic, cholesterol, and weight effects of L carnitine in diabetes: A systematic review and meta analysis of randomized controlled trials ScienceDirect When to Take L Carnitine for Weight Loss & Maximize Results L carnitine is a naturally occurring amino acid structure that is made in the human brain, liver, and kidneys. L carnitine plays a critical role in energy production, as it converts fat into energy.