L Carnitine: Benefits, Side Effects, FAQ, Sources, and Dosage Over 90% of your body's energy comes from mitochondria. When they break down, everything else does too. Think: Fatigue that sleep doesn't fix Brain fog and memory issues Slow l Carnitine and heart disease ScienceDirect The adverse effects of long term l carnitine supplementation on liver and kidney function in rats L Liu, D M Zhang, M X Wang, C Y Fan, F Zhou, S J Wang, L D Kong, 2015 L Carnitine is Underrated. New Meta Review Reminds Us Why. Comparison of short term and long term effects of peroral L carnitine intake: clinical implications of elevated TMAO levels in cardiovascular complications