L-Carnitine for Weight Loss

Can It Help You Lose Weight?

Overweight girl looking at underweight reflection
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L-carnitine is a nutrient widely available in supplement form and often marketed as a weight loss aid. Made naturally in the body, L-carnitine is essential for transporting fat into cells to produce energy.

While many supplement manufacturers claim that L-carnitine can speed up metabolism, there is little scientific support for L-carnitine's ability to promote weight loss.

Health Benefits of L-Carnitine for Weight Loss

To date, few clinical trials have tested l-carnitine's effectiveness as a weight loss aid. The available research includes a 2000 study from the International Journal of Sport Nutrition and Exercise Metabolism, in which 36 moderately overweight premenopausal women were given either L-carnitine or a placebo twice daily for eight weeks. Analyzing study results, researchers found no difference in total body mass or fat mass between those who took L-carnitine and those given the placebo.

A number of animal studies have also shown that L-carnitine may not support weight loss. A 2002 study from the Annals of Nutrition and Metabolism, for instance, found that rats treated with l-carnitine did not experience a greater reduction in body fat levels compared to a control group.

What's more, a 2005 study published in the International Journal for Vitamin and Nutrition Research found that rats fed an L-carnitine-enhanced diet tended to gain more weight than other animals in the study (despite no difference in their intake of calories).


In some cases, L-carnitine supplements may produce certain side effects (including nausea, abdominal cramps, diarrhea, and a "fishy" body odor). In addition, L-carnitine may interact with antibiotics used in the long-term prevention of urinary tract infections (such as pivampicillin).

Using L-Carnitine

Supplements haven't been tested for safety and due to the fact that dietary supplements are largely unregulated, the content of some products may differ from what is specified on the product label. Also keep in mind that the safety of supplements in pregnant women, nursing mothers, children, and those with medical conditions or who are taking medications has not been established. You can get tips on using supplements here, but if you're considering the use of L-carnitine, talk with your primary care provider first. Self-treating a condition and avoiding or delaying standard care may have serious consequences.

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Article Sources
  • Brandsch C, Eder K. "Effect of L-carnitine on Weight Loss and Body Composition of Rats Fed a Hypocaloric Diet.​" Ann Nutr Metab. 2002;46(5):205-10.
  • Melton SA, Keenan MJ, Stanciu CE, Hegsted M, Zablah-Pimentel EM, O'Neil CE, Gaynor P, Schaffhauser A, Owen K, Prisby RD, LaMotte LL, Fernandez JM. "L-carnitine Supplementation Does Not Promote Weight Loss in Ovariectomized Rats Despite Endurance Exercise.​" Int J Vitam Nutr Res. 2005 Mar;75(2):156-60.
  • Office of Dietary Supplements. "Dietary Supplement Fact Sheet: Carnitine". 
  • Villani RG, Gannon J, Self M, Rich PA. "L-Carnitine Supplementation Combined With Aerobic Training Does Not Promote Weight Loss in Moderately Obese Women." Int J Sport Nutr Exerc Metab. 2000 Jun;10(2):199-207.