Carnitine: Genetic Variants Affecting Mitochondrial Energy and Health Frontiers Association between fatigue, peripheral serotonin, and L carnitine in hypothyroidism and in chronic fatigue syndrome Understanding the Role of Carnitine in TPN and IDPN Therapy Signs & Symptoms of L Carnitine Deficiency L Carnitine L Tartrate: 8 Key Benefits Dr. Lam If you are like a lot of people, you may have never heard of carnitine but this important nutrient is critical for our body's ability to optimally burn fat required for energy.