Q & A Library

L-carnitine is an amino acid, and it can be a wonderful supplement, if you need it. Amino acids are the building blocks of protein molecules. They're relatively simple natural substances that are the first breakdown products of protein in digestion. If you eat adequate protein (and most people in this country get more than enough), you will have all the amino acids you need and probably more. There is no need to take pricey mixtures of amino acids as often recommended by fitness instructors, bodybuilders and athletes to build muscle mass.

Single amino acids are another matter. To achieve a beneficial effect, take one on an empty stomach in order to build up high levels in the blood and brain. A number of individual amino acids, including L-carnitine, are available in health food stores. L-carnitine is heavily promoted for use as a supplement to increase muscle strength and energy, to burn fat (for weight loss), for multiple sclerosis, Parkinson's disease, diabetes, chronic fatigue and a host of other problems.

It is true that L-carnitine aids in muscle metabolism and is protective of heart muscle. However, I don't recommend taking it except when combined with other treatments for the following serious heart conditions:

• Cardiomyopathy, a disease of heart muscle that often occurs in young people, sometimes following a viral infection. Try 1,000 mg twice a day. 
• Angina, or angina pectoris, a distressing symptom of coronary insufficiency that often predicts heart attacks. L-carnitine can help by improving heart muscle metabolism. Again, the recommended dose is 1,000 mg twice a day. 
• Cardiac arrhythmia, a term for irregular heart beat that can range from harmless to life-threatening, is another disorder for which L-carnitine may be useful. Take 500-1,000 mg twice a day.
• Congestive heart failure occurs when the heart doesn't pump as well as it should, usually because it has been weakened by clogged arteries, high blood pressure, a defect in its muscular walls or some other medical problem. The dosage is 500-1,000 mg twice a day. 
• Atrial fibrillation, a disorder in which the two upper chambers of the heart quiver instead of beating in an organized and efficient fashion. I recommend 300-600 mg of L-carnitine three times a day to help increase the efficiency of the heart's pumping activity. 

Andrew Weil, M.D.