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 Acetyl L Carnitine 500mg Health Thru Nutrition Acetyl L Carnitine Powder 3.53 oz (100 Grams) Vital Nutrients PureFormulas 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. BulkSupplements.com L Carnitine Tartrate Powder Carnitine Supplement, L Carnitine L Tartrate, L Carnitine 1000mg Unflavored & Gluten Free, 1000mg