Updated: Jul 10, 2020
L-carnitine is an amino acid that is produced in the body. L-carnitine helps the body turn fat into energy. The body can convert L-carnitine to other amino acids called acetyl-L-carnitine and propionyl-L-carnitine. But, no one knows whether the benefits of these other carnitines are the same. Until more is known, don't switch one form of carnitine for another.
L-carnitine is taken by mouth to increase L-carnitine levels in people whose natural level of L-carnitine is too low. Some people also use L-carnitine for conditions of the heart and blood vessels.
How does it work?
L-carnitine helps the body produce energy. It is important for heart and brain function, muscle movement, and many other body processes.
Involuntary weight loss in people who are very ill (cachexia or wasting syndrome). Early research shows that taking L-carnitine can increase body mass index (BMI) and improve lean body mass in people with cancer and wasting syndrome. Also, taking L-carnitine in combination with antioxidants and certain prescription drugs used to increase appetite seems to improve lean body mass better than taking the prescription drugs alone.
Obesity. Some research shows that taking L-carnitine can improve weight loss in adults. L-carnitine seems to work best when taken along with weight-loss drugs such as orlistat or sibutramine and when used by people with diabetes.
Athletic performance. Intense exercise has been linked to a decrease in L-carnitine blood levels and some studies show that L-carnitine improves athletic performance and endurance.
When taken by mouth: L-carnitine is LIKELY SAFE when taken for up to 12 months. It can cause side effects such as nausea, vomiting, stomach upset, heartburn, diarrhea, and seizures. It can also cause the urine, breath, and sweat to have a "fishy" odor. Avoid using D-carnitine and DL-carnitine. These forms of carnitine might block the effects of L-carnitine and cause symptoms that resemble L-carnitine deficiency.
For L-carnitine deficiency: 990 mg two to three times daily in tablets or as an oral solution.