L carnitine supplements can cause a fishy odor in the breath, sweat, and urine. This is likely due to the formation of trimethylamine (TMA). TMA is also responsible for the pungent smell of 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 Did You Know? Some people report a fishy smell after supplementing with L carnitine. This happens because certain gut bacteria convert carnitine to trimethylamine, a malodorous compound found in rotting fish. The effect of l carnitine supplementation on mortality and clinical outcomes in ventilator dependent critically ill patients with obesity and COVID 19: Protocol for a randomized double blind placebo controlled trial ScienceDirect Treatments of trimethylaminuria: where we are and where we might be heading ScienceDirect L Carnitine Pills for Weight Loss: Evidence, Safety and UK Guidance Bolt Pharmacy