If you're putting in the work but the scale isn't moving, your body might just need a little help tapping into its fat stores. That's where L Carnitine comes in. It's not a L carnitine is a naturally occurring amino acid structure that is made in the human brain, liver, and kidneys. L carnitine plays a critical role in energy production, as it converts fat into energy. The Role of L Carnitine in Kidney Disease and Related Metabolic Dysfunctions The Science of Carnitine: How It Works and Why It Matters