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Enjoy sex like you used to
Reviewed by Felix Gussone, MD
Written by Lauren Panoff, MPH, RD
Published 06/02/2023
Updated 03/04/2025
Some people claim they use L-citrulline supplements for erectile dysfunction (ED) and see results. But has research confirmed L-citrulline’s benefits for ED? And if so, how long does it take for L-citrulline to work for ED?
While some research has shown that L-citrulline can offer health benefits, both the number of studies and the overall data are very limited.
And because there hasn’t been any large study on L-citrulline’s benefits for males dealing with ED, it isn’t clear how long it takes for L-citrulline to work for this issue.
To understand what this means for you and the viability of this alternative treatment option for ED, read on.
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To understand how L-citrulline might help ED, let’s get into a bit of the science behind how erections work.
When you feel sexually aroused, your nervous system sends a signal to the tissue inside your penis, known as the corpora cavernosa. The blood vessels that supply blood to your penis then dilate, increasing blood flow and creating an erection.
One molecule that’s involved in this process is nitric oxide. This molecule plays a key role in relaxing the smooth muscle tissue that controls blood flow to the erectile tissue inside your penis. During this process, an amino acid produced by the body, L-citrulline, becomes important. That’s because L-citrulline is transformed within the body into L-arginine, a different amino acid, which then becomes nitric oxide.
Put simply, L-citrulline converts into L-arginine, which then transforms into nitric oxide—an essential compound that enhances blood flow to the penis by relaxing blood vessels.
This is where L-citrulline supplementation comes in: Some people take L-citrulline supplements to produce L-arginine, which improves blood flow by creating nitric oxide, a gas that helps widen blood vessels and lower blood pressure.
Note that it’s also possible to get L-citrulline through foods, namely watermelon, but also legumes and meat.
Beyond ED, some people also use L-citrulline supplementation or L-citrulline malate (one of the forms of citrulline that’s a combination of L-citrulline with malic acid) for improved athletic performance and exercise performance or to improve muscle strength or reduce muscle soreness after a tough workout. It’s also been shown to help people with heart disease and improve arterial blood flow and reduce blood vessel stiffness, but more research is needed in this area.
As we mentioned above, L-citrulline converts to L-arginine, which increases nitric oxide production to widen blood vessels.
Healthy blood flow and proper vasodilation is an important part of how erections work, so in theory, L-citrulline could help reduce ED by increasing blood flow to your penis.
L-arginine supplementation (or even nitric oxide supplements like nitrates) is typically not the most efficient way to produce nitric oxide, which is why people may use L-citrulline supplements to increase arginine levels and produce a normal erection.
You may see L-arginine marketed as a natural remedy for erectile dysfunction, but there isn’t much evidence to support this claim, even for mild ED.
Because ED is an incredibly common health condition for men (between 30 and 50 million are affected in the U.S. alone), the number of treatments available is vast.
So people searching the internet for “L-citrulline benefits for males” probably hope to see a lot of studies explaining the potential benefits.
Unfortunately, the current research on L-citrulline for ED is also very limited.
One small study of 24 men with moderate or mild erectile dysfunction found that oral citrulline supplementation could improve erection hardness scores and overall sexual satisfaction.
Another even smaller study of 13 men similarly found that oral L-citrulline supplementation was effective in treating ED. This treatment, however, was a combination of citrulline supplementation with a polyphenol known as resveratrol and a PDE5 inhibitor — the first line of treatment for most men with ED.
Still, there haven’t been any large randomized clinical trials to assess the safety of L-citrulline for ED treatment.
There are proven treatments for ED, from prescription medications to addressing sexual performance anxiety and other root causes of psychological ED.
However, some men may prefer to try L-citrulline — and even alternatives like drinks for ED or eating foods to help with ED — when they don’t want to start taking the usual ED medications right away or they experience too many side effects.
Because there hasn’t been a large study to assess whether L-citrulline supplementation improves erection health, the answer to “How long does it take for L-citrulline to work for ED?” isn’t clear.
The duration of treatment for both studies we mentioned above was two months, with patients taking a placebo (an inactive drug) for one month, followed by another month of oral citrulline supplementation.
More research would be needed to fully understand not only how long L-citrulline takes to work for ED, but also whether oral citrulline supplementation is effective when it comes to getting harder erections.
The exact L-citrulline dosage for ED is also unclear, once again, due to the limited amount of research.
In the first study on oral L-citrulline supplementation we mentioned, patients received a dosage of 1.5 grams of citrulline each day for a month. Meanwhile, the second study saw patients receive 800 milligrams of L-citrulline along with 300 milligrams of transresveratrol each day.
If you search online, you’ll find sources recommending an L-citrulline dosage of 2,000 milligrams three times a day, or 1.76 grams of citrulline malate for erectile dysfunction. However, there isn’t sufficient research to support this dosage. Before adding any supplements to your routine it’s always a good idea to consult your healthcare provider.
Though research on the effectiveness of L-citrulline for ED is limited, this dietary supplement is believed to be safe. Citrulline has been used as an oral supplement for many years without reports of serious safety concerns. However, the FDA states that due to limited safety data, potential risks cannot be ruled out.
Generally speaking, any supplement or medication that causes vasodilation or otherwise affects blood pressure should not be taken without medical advice first, especially if the person is taking other medications to address high blood pressure or similar issues.
In other words, if you want to take oral L-citrulline supplements for ED, consult with a healthcare provider first.
Erectile dysfunction is the inability to attain and maintain an erection sufficient for sexual satisfaction, and it affects many men.
Fortunately, there are several treatment options out there that are proven to work. For instance, something as simple as lifestyle changes, like an improved diet or increases in exercise, is sometimes enough for men with mild erectile dysfunction.
You might even consider different types of therapy, as depression and anxiety can sometimes play a role in ED.
But when it comes to L-citrulline supplements as a possible treatment option for ED, here’s our take:
An amino acid produced by the body, L-citrulline, may help create more nitric oxide, which, in turn, helps promote healthy blood flow.
Increased blood flow is one part of the process of getting an erection. So many people may turn to L-citrulline supplements to increase blood flow and reduce ED.
The research on L-citrulline for ED is thin. And while this supplement doesn’t appear to have significant adverse effects, there are many other proven treatments for erectile dysfunction to consider.
One of the most common treatments is a class of oral medications known as PDE5 inhibitors. These are FDA-approved and work by relaxing the blood vessels and increasing blood flow to your penis to improve erectile function.
The most common PDE5 inhibitors are sildenafil (the active ingredient in Viagra®), tadalafil (Cialis®), vardenafil (Levitra), and avanafil (Stendra®). They’re available as either oral medications or chewable ED mints.
While a natural treatment like L-citrulline may sound more appealing, there is plenty of research to support the safety and effectiveness of prescription medications.
If concerns about possible medication side effects or drug interactions are why you’re weighing options like L-citrulline for ED, connect with a healthcare provider. They can help you find the right option, and from there, you can explore ED treatments available online from Hims.
Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references. See a mistake? Let us know at [email protected]!
This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.
Dr. Felix Gussone is a medical content specialist and Medical Advisor at Hims & Hers. Prior to joining Hims & Hers, Felix worked in digital health at Ro, focusing on patient education.
Raised in Germany, Dr. Gussone earned his M.D. from Ludwig-Maximilians-University before transitioning into health journalism and medical education content. He currently leads the medical information content team at an American biotech company.
Throughout his career, Dr. Gussone has used his medical expertise to drive the development of evidence-based health content and patient education materials. He has over 10 years of experience covering a wide range of topics, including health news, diet and weight loss, mental health, and sexual health, for prominent television programs and online publications.
Dr. Gussone has contributed to leading television programs such as CNN’s Anderson Cooper 360, NBC TODAY, and NBC Nightly News with Lester Holt, where he produced and wrote a wide range of health and wellness stories for television and digital outlets that engaged and informed diverse audiences across the United States and abroad. In addition to his work in cable and network health reporting, Felix served as Senior Health Editor at Elemental, Medium’s health and wellness publication, where he led editorial content development focused on science and personal well-being.
Dr. Gussone lives in Cambridge, Massachusetts and Brooklyn, and enjoys perfume making, scuba diving, roller blading, and traveling. You can find Dr. Gussone on LinkedIn for more information.