The Role of L Carnitine in Kidney Disease and Related Metabolic Dysfunctions 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: 5% Nutrition Rich Piana Liquid L Carnitine 3150 Premium 4 Source Blend + GBB, The Super Carnitine (Mandarin Orange) : Health & Household 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. 11 Urine Smells Explained In Everyday Life Some food and drink habits show up in a very ordinary place, and people are always a little surprised by how fast it happens. A L Carnitine: Benefits, side effects, and dosage