Some supplements that can lower blood sugar may lower it too much if you take them with medication. Other supplements may raise blood sugar. See link below PDF) Comparison of pharmacokinetics of L carnitine, Acetyl L carnitine and Propionyl Lcarnitine after single oral administration of L carnitine in healthy volunteers Our cardiologist explains which vitamins and supplements to avoid with high blood pressure. The Role of L Carnitine in Kidney Disease and Related Metabolic Dysfunctions