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: Benevolent L Carnitine Supplement High Potency 1500mg L Carnitine Tartrate Fast Absorbing, Convert Fat to Energy, Support Lean Muscle, Boost Workout Performance & Metabolism 120 Vegan Capsules : Health & Household L Carnitine Liquid Tropical Punch 1000 mg, 16 oz. NOW Foods Fruitful Yield L Carnitine Side Effects & Safety: A Complete Guide The Science of Good Health