L Carnitine for Weight Loss: How It Works, Dosage & Best Supplement Zeelab Pharmacy Best Time to Take L Carnitine: A Complete Guide The Science of Good Health How Long Should You Take L Carnitine for Weight Loss Results? Supplements don't replace the workbut they can support it L Carnitine helps your body turn fat into usable energy, so you can push harder and recover better. Consistency first. Supplements second. Results Should I use L Carnitine on rest days or just before workouts?