WHAT IS L'CARNITINE? L'Carnitine is like a taxi for fat molecules, helping them get into cells to produce energy. It's found naturally in meat and dairy and can help with burning fat, Do You Know How Long It Takes L carnitine To Start Working? Plix L Carnitine Liquid Benefits Explained: A Guide The Science of Good Health L Carnitine Linus Pauling Institute Oregon State University 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.