Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum Trimethylaminuria: Definition, symptoms, and more 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. Your urine's smell can reveal a lot about your health. A strong ammonia like odor could indicate kidney stress, while a fruity scent may suggest ketones. Sweet smelling urine might point to diabetes risk, Does Carnitine Cause Body Odor? Lume Deodorant