L-carnitine, which is normally manufactured by the human body, has been popular as a potential ergogenic aid (i.e., having the ability to increase work capacity), because of its role in the conversion of fat to energy.1 However, while some studies have found that L-carnitine improves certain measures of muscle physiology, research on the effects of 2 to 4 grams of carnitine per day on performance have produced inconsistent results.2 L-carnitine may be effective in certain intense exercise activities leading to exhaustion,3 but recent studies have reported that L-carnitine supplementation does not benefit non-exhaustive or even marathon-level endurance exercise,4, 5 anaerobic performance,6 or lean body mass in weight lifters.7