L Carnitine, 500 mg, 60 Vegetarian Capsules 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. Exploring the Efficacy of Carnitine as a Dietary Supplement L Carnitine: Benefits, side effects, and dosage Veterinary Strength Healthy Heart for Dogs & Cats Trimethylaminuria (Fish Odor Syndrome or TMAU)