Page 1 Reviews The Vitamin Shoppe, Acetyl L Carnitine , 500 mg , 240 Capsules iHerb 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 What Is L Carnitine? How Does It Work? How to Choose the Best L Carnitine Supplement: A Smart Shopper's Guide Life Extension