Carnitine: the claims and why it may not work L Carnitine Is L Carnitine safe for athletes at doses up to 6000 mg day? Consensus 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: Benefits, Uses, and Side Effects Lifespan Research Institute