Acetyl-L Carnitine 500 mg 50 vcaps by NOW Laboratories contains a specialized form of l-carnitine. L-carnitine is a critical amino acid for human growth and development. While the body can produce l-carnitine on its own. a variety of medical issues and nutrient deficiencies can impact levels of this essential amino acid. An l-carnitine deficiency is associated with sexual dysfunction. muscle loss. apathy. poor memory and a variety of other negative health effects.