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.

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.

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.

Not every man experiencing ED will want to use conventional prescription medications. Other nondrug treatments exist. If you’re looking for natural remedies to improve your ED symptoms, these might be good places to start. But as with all natural remedies, consult your doctor before taking anything. Learn about other natural treatments for erectile dysfunction.

Penile pumps

Penile pumps are a noninvasive way to treat ED. They’re used just before sexual intercourse to increase blood flow to the penis. If used incorrectly, they can cause bruising and pain.

Penile implants

Implants can be surgically inserted into the penis and then inflated prior to sexual intercourse.


Panax ginseng has been shown in multiple peer-reviewed studies to be a safe, effective treatment for ED.


Dehydroepiandrosterone (DHEA) is a hormone naturally produced by the body’s adrenal glands. Although there are no recent studies, one older study showed that men with ED often have low DHEA levels. Supplementing those levels might also help improve muscle strength in older adults. However, more up-to-date research is needed.


This form of complementary medicine involves sticking needles into upper layers of skin and tissue. This practice has been used for centuries to ease pain, alleviate chronic problems, and treat various conditions.

One study in the International Journal of Impotence Research found that about a quarter of the men in the study who received acupuncture had improved erections and were able to perform sexually.

If you have ED and want to find a way to improve your symptoms, talk with your doctor.

If you’re concerned about taking traditional ED medications, such as sildenafil (Viagra) or tadalafil (Cialis), because of potential side effects, talk to your doctor about other options.

Supplements such as L-citrulline and natural remedies show some promise in the treatment of ED. Your doctor can help you find a treatment plan that is safe and less likely to cause side effects.

Sometimes men are hesitant to talk about these sensitive issues, but the sooner you ask for help, the sooner you can find answers and the treatment you need.

Something important to note is that there are no alternative supplements shown to definitively manage the symptoms of erectile dysfunction. Also, one-third to one-half of supplements marketed as natural products actually contain synthetic chemicals. The most common is PDE-5 inhibitors or analogs of PDE-5 inhibitors, which are used in Viagra.

There is also concern that people who are taking nitrates for heart conditions may experience dangerous drops in their blood pressure when taking these supplements. So, it’s very important to always speak with your doctor before starting to take a supplement. Read more about doctors who treat erectile dysfunction here.