L Carnitine for Cutting vs Bulking: How It Works in Both Phases L Carnitine Benefits, Uses, Dosage, Foods, Side Effects Dr. Axe L Carnitine 1500 mg with Vitamin B Promote Physical Performance MaxionNutrition When to take L carnitine: Dosage, forms, and side effects From brain to muscle, L Carnitine plays a key role in energy metabolism, endurance, and recovery by supporting efficient fat to energy conversion.