Frontiers Association between fatigue, peripheral serotonin, and L carnitine in hypothyroidism and in chronic fatigue syndrome Comparison of short term and long term effects of peroral L carnitine intake: clinical implications of elevated TMAO levels in cardiovascular complications Carnitine Deficiency: What Is It, Causes, Symptoms, and More Osmosis The effects of L carnitine supplementation on lipid profiles in adults: A systematic review and dose response meta analysis ScienceDirect 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.