Medically reviewed by Shuvani Sanyal, M.D. — Written by Kimberly Holland — Updated on October 4, 2018

What is L-citrulline?

L-citrulline is an amino acid normally made by the body. The body converts L-citrulline to L-arginine, another type of amino acid.

L-arginine improves blood flow. It does so by creating nitric oxide (NO), a gas that helps dilate blood vessels. L-arginine has been shown to help people with heart disease or clogged arteries because of its vessel-widening abilities. Learn more about the benefits of L-arginine.

The same effect on blood vessels helps improve symptoms of erectile dysfunction (ED). The L-citrulline to NO path increases blood flow to a man’s genitals. In one study, this increase in blood flow appeared to decrease symptoms of mild ED and improve the ability to maintain an erection. There haven’t been any studies on the use of L-citrulline in moderate to severe cases of ED.

 

How can you get L-citrulline in your diet?

Watermelon is one of the best food sources of L-citrulline. Legumes, meat, and nuts also contain the amino acid. But most people use supplements to increase the amount of L-citrulline in their diets.

L-citrulline supplements are available over the counter. But few credible peer-reviewed studies have looked at the proper dosing for L-citrulline, so no official dosing recommendations exist.

However, one study from the British Journal of Nutrition found that doses between 2 and 15 grams (g) were safe and well-tolerated by the men in the study.

Supplements available in stores range from 500 milligrams (mg) to 1.5 g. Some supplements contain a mixture of L-citrulline and other ingredients. Read the supplement label to see exactly how much of the amino acid you’re getting with each dose.

Concerns and side effects

The research to support the use of L-citrulline as an ED treatment is limited. Treatment with traditional ED medications — such as the phosphodiesterase type 5 inhibitors Cialis, Levitra, and Viagra — has proven to be very effective.

Some men prefer not to use those medications because of possible risks or side effects. This may be true especially for men who experience only mild ED. In those cases, the use of L-citrulline may be preferable, at least for short periods of time. L-citrulline is believed to be safe, as studies haven’t yet found any known side effects. However, there has been no large randomized clinical trial to assess the safety of L-citrulline for ED treatment.

If you’re taking any other medications, it’s important you talk with your doctor about possible interactions. This is especially important in the context of other medications that also work to dilate your blood vessels. L-citrulline supplements may have additional synthetic ingredients similar to traditional ED medications. Simultaneous use of L-citrulline supplements with other vasodilatory drugs can cause dangerous drops in blood pressure.