L-carnitine acts as a buffer of acetyl-CoA units in the mitochondria, as well as facilitating transport of fatty acids. In addition, L-carnitine levels are decreased in the diabetic heart. The purpose of this study was to investigate the effect of L-carnitine supplementation on cardiac function and metabolism in the diabetic rat heart. We show that daily injections of L-carnitine can alter cardiac metabolism in the in-vivo diabetic rat heart, and can improve functional recovery as well as fatty acid oxidation rates post ischemia. Such studies allow a better understanding of the interactions between metabolism and function in the diabetic heart and may provide new insight into novel therapeutics.