While as little as 1 gram of L-carnitine can be effective, your best bet is to take 2-3 grams per dose for maximum benefit, along with at least 30-40 grams of carbs and 20-40 grams of protein, preferably with a meal. This applies if you take straight-up L-carnitine, L-carnitine L-tartrate, or propionyl-L-carnitine.