L-Carnitine

Amino-acid derivative that shuttles long-chain fatty acids into the mitochondria for beta-oxidation. Used as an injectable for fat-loss and exercise recovery/performance, and a common base of "lipotropic"/MIC injection stacks. Oral carnitine is poorly bioavailable (the main reason for injectable interest), and the human fat-loss evidence is modest and population-dependent, so benefits should be treated as preliminary outside of documented deficiency.