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 Amazon.com: NOW Foods Supplements, L Carnitine 1,000 mg, Purest Form, Amino Acid, Fitness Support*, 100 Tablets : Health & Household Potential Adverse Effects of L Carnitine Marnys 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. LCarnitine Liquid 3000 mg Fast Absorbing Energy Support Muscleology Muscleology Sports Nutrition