When to Take L Carnitine for Optimal Training Benefits Transparent Labs L Carnitine as Pre Workout Supplement: Guide The Science of Good Health L Carnitine L Tartrate 1000 mg for Energy & Fat Metabolism Support Carbamide Forte L Carnitine 2175mg per serving 200 Capsules Oxyenergys L Carnitine. My go to pre post workout supplement. Pre workout I usually take it before my workout session for energy production. Post workout Ill take it the day after my workout