Acetyl L Carnitine: Benefits and Side Effects Gene Food Is L Carnitine safe for athletes at doses up to 6000 mg day? Consensus Should I use L Carnitine on rest days or just before workouts? Acetyl L Carnitine is more thought of as a fat burner. It's actually powerful tool for athletes looking to improve endurance, energy, and mental performance. Here's how you can integrate it into your routine for