L Carnitine: The Energy Booster Your Body Loves Turn fat into fuel and power up your recovery with one of our favorite performance vitamins. Boosts metabolism & fat burning Lily Green Supplements: Acetyl L Carnitine 1000mg for Energy & Focus Nature's Bounty L Carnitine 500 Mg 30 Tablets Nahdi Acetyl L Carnitine 1000mg Brain, Energy, Metabolism Support Purecell Supplements L carnitine is a naturally occurring amino acid structure that is made in the human brain, liver, and kidneys. L carnitine plays a critical role in energy production, as it converts fat into energy.