Frontiers Newborn Screening and Genetic Analysis Identify Six Novel Genetic Variants for Primary Carnitine Deficiency in Ningbo Area, China Full article: Effects of high dose L carnitine supplementation on diaphragmatic function in patients with respiratory failure: A randomized clinical trial What are the symptoms of carnitine (L carnitine) deficiency? 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.