Free Form Amino Acid. Dietary Supplement. Twinlab L-Carnitine capsules are easier to swallow and assimilate. . Twinlab L-Carnitine Capsules contain no synthetic D-Carnitine or DL-Carnitine. D-Carnitine and DL-Carnitine are less effective than L-Carnitine. D-Carnitine and DL-Carnitine are not recommended because of their adverse physical side effects. Well tolerated by most highly allergic individuals. No tablet binders coatings or colorings.