Adding L Carnitine and Selenium to Methimazole in Graves' Disease: A Prospective Randomized Trial on Thyroid Markers and Quality of Life L Carnitine Tablets for Energy Support Nature's Bounty If you are like a lot of people, you may have never heard of carnitine but this important nutrient is critical for our body's ability to optimally burn fat required for energy. Amazon.com: Horbach L Carnitine Supplement 500mg 60 Capsules as L Carnitine L Tartrate Non GMO and Gluten Free : Health & Household L Carnitine Fumarate, 180 Veggie Caps (500 mg per Veggie Cap)