Early research into L carnitine was often cited as underwhelming, showing negligible changes in muscle carnitine content and fat loss outcomes. However, these findings may have been limited by a short study window L Carnitine is Underrated. New Meta Review Reminds Us Why. Frontiers Association between fatigue, peripheral serotonin, and L carnitine in hypothyroidism and in chronic fatigue syndrome Does L carnitine produce a clinically meaningful effect within four hours? L Carnitine Linus Pauling Institute Oregon State University