Does L carnitine cause fishy body odor? Surprising Truth and Solutions Tonum Too Much L Carnitine Smell Fishy TikTok When a 12 month old boy in Portugal developed an unexpected and persistent smell similar to rotting fish, his parents were unsettled. The child appeared healthy, showed no signs of infection, and behaved normally. Does Carnitine Cause Body Odor? Lume Deodorant 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.