Some things you try once and forget about and then there are things that actually stick because they WORK. L Carnitine is one of those for me. Here's why It Carnitine: the claims and why it may not work Neither L Carnitine nor Berberine work like caffeine, yohimbine, or fat burners. They do NOT: Spike your heart rate Jack up your nervous system Cause jitters or crashes Mask L Carnitine: Benefits, Side Effects, Sources, and Dosage iMuscles Nutrition Burn fat. Keep muscle. Perform better., L Carnitine helps your body turn fat into fuelso your workouts actually work.