How Much L Carnitine Per Day: Expert Guide The Science of Good Health Frontiers Association between fatigue, peripheral serotonin, and L carnitine in hypothyroidism and in chronic fatigue syndrome L Carnitine doesn't magically burn fat, it helps your body use fat as energy. Combine it with training and consistency, and you'll feel the difference @Marybosch shows us how L Carnitine will boost your 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.