Acetyl-L-Carnitine (ALCAR) is L-carnitine bound to an acetyl group. This form of carnitine is known as the neurological variant of L-carnitine because it can pass through the blood-brain barrier. As a result, it has more interactions with the central nervous system. These unique properties cannot be attributed to other forms of carnitine.

L-Carnitine Fumarate is bound to fumaric acid. L-Fumarate is a substance that occurs naturally in the body as a citric acid cycle intermediate; in this cycle energy (ATP) is produced. Just as vitamin D3, fumaric acid is produced in the skin when exposed to direct sunlight. Fumaric acid coupled to the L-carnitine part creates a synergistic whole. This form is widely used as an energy booster and to assist with weight loss.

L-Carnitine L-tartrate (LCLT) is L-carnitine bound to tartaric acid, and is absorbed faster than other L-carnitine variants. The rapid influx makes this form particularly suitable for time-critical situations, such as immediately before or after sporting activities and as such the supplement is mainly used by athletes. Also, L-carnitine L-tartrate interacts with hormones such as testosterone, moderating the availability of androgen receptors.