Acetyl L Carnitine vs L Carnitine: 4 Key Differences Momentous L Carnitine has become one of our top 5 sellers the last few years and when you review the research, you can see why. L carnitine is a supplement probably more well known if Muscle Specific Deletion of Carnitine Acetyltransferase Compromises Glucose Tolerance and Metabolic Flexibility ScienceDirect Carnitine supplementation improves metabolic flexibility and skeletal muscle acetylcarnitine formation in volunteers with impaired glucose tolerance: A randomised controlled trial eBioMedicine