L Carnitine Dosage for Erectile Dysfunction The Right Way to Take L Carnitine to Boost Your Training 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 The adverse effects of long term l carnitine supplementation on liver and kidney function in rats L Liu, D M Zhang, M X Wang, C Y Fan, F Zhou, S J Wang, L D Kong, 2015