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. How to Inject L Carnitine for Weight Loss Safely 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: Nutricost Acetyl L Carnitine (ALCAR) 500mg, 180 Capsules, 180 Servings Non GMO and Gluten Free, 1 Capsule per Serving : Everything Else