L-Carnitine is a nonessential organic nutrient, ubiquitous in all the cells of the organism, required for entry of longchain fatty acids into mitochondria, where they are burned for energy. Fat burning is a major source of muscular energy, so deficiencies in L-Carnitine are manifested as low energy levels and muscular weakness. L-Carnitine deficiencies can also appear as mental confusion or cloudiness, angina (heart pain) and weight gain.