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How Long Does It Take for L-Citrulline to Work for ED?

Kelly Brown MD, MBA

Reviewed by Kelly Brown MD, MBA

Written by Geoffrey C. Whittaker

Published 06/02/2023

Updated 04/05/2024

Some people claim they use L-citrulline supplements for erectile dysfunction (ED) and see results. But has research confirmed L-citrulline 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 ED benefits, the data and study volume is very, very limited. And because there hasn’t been any large study on L-citrulline benefits for males dealing with ED, it isn’t clear how long it takes for L-citrulline to work for ED.

To understand what this means for you and the viability of this alternative treatment option for ED, read on.

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, is converted to L-arginine, another type of amino acid. 

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. 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 or clogged arteries.

L-Citrulline vs L-Arginine

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 (around 30 million are affected in the U.S. alone), the number of treatments available is vast. So people googling “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 was an effective treatment in improving erection hardness scores and overall sexual satisfaction.

  • Another small 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 the usual ED medications don’t work or they experience too many side effects.

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Since 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.

Choose your chew

The exact L-citrulline dosage for ED is also unclear, once again due to the limited amount of studies.

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.

One source recommends an L-citrulline dosage of 2,000 milligrams three times a day, or 1.76 grams of citrulline malate for every 1 gram of citrulline you might take for circulatory health. However, there isn’t much research to support this dosage.

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.

In fact, a review of citrulline malate supplements found only a couple of mild L-citrulline side effects were experienced:

  • Nausea

  • Diarrhea

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 taking it takes 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.

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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. For instance, something as simple as lifestyle changes, like an improved diet or increases to exercise is sometimes even 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 to 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 an oral medication known as PDE5 inhibitors. These work by relaxing the arteries 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, prescription medications have plenty of research to support their effectiveness. 

If concerns about possible medication side effects or drug interactions is why you’re weighing options like L-citrulline for ED, talk to your healthcare provider. They can help you find the right option, and from there, you can explore ED treatments available online from Hims.

12 Sources

  1. Definition & Facts for Erectile Dysfunction - NIDDK. (n.d.). National Institute of Diabetes and Digestive and Kidney Diseases. Retrieved from https://www.niddk.nih.gov/health-information/urologic-diseases/erectile-dysfunction/definition-facts
  2. Allerton, T. D., Proctor, D. N., Stephens, J. M., Dugas, T. R., Spielmann, G., & Irving, B. A. (2018). L-Citrulline Supplementation: Impact on Cardiometabolic Health. Nutrients, 10(7). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073798/
  3. Gough, L. A., Sparks, S. A., McNaughton, L. R., Higgins, M. F., Newbury, J. W., Trexler, E., Faghy, M. A., & Bridge, C. A. (2020). A critical review of citrulline malate supplementation and exercise performance. European Journal of Applied Physiology, 121(12), 3283-3295. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8571142/
  4. Panchatsharam, P.K., Durland, J. & Zito, P.M. (2022, May 8). Physiology, Erection. StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK513278/
  5. Davies, K. P. (2015). Development and therapeutic applications of nitric oxide releasing materials to treat erectile dysfunction. Future Science OA, 1(1). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4806684/
  6. Dietary Supplements for Exercise and Athletic Performance - Health Professional Fact Sheet. (n.d.). NIH Office of Dietary Supplements. Retrieved from https://ods.od.nih.gov/factsheets/ExerciseAndAthleticPerformance-HealthProfessional/#citrulline
  7. Cormio, L., De Siati, M., Lorusso, F., Selvaggio, O., Mirabella, L., Sanguedolce, F., & Carrieri, G. (2011). Oral L-Citrulline Supplementation Improves Erection Hardness in Men With Mild Erectile Dysfunction. Urology, 77(1), 119-122. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S0090429510016614
  8. Shirai, M., Hiramatsu, I., Aoki, Y., Shimoyama, H., Mizuno, T., Nozaki, T., Fukuhara, S., Iwasa, A., Kageyama, S., & Tsujimura, A. (2018). Oral L-citrulline and Transresveratrol Supplementation Improves Erectile Function in Men With Phosphodiesterase 5 Inhibitors: A Randomized, Double-Blind, Placebo-Controlled Crossover Pilot Study. Sexual Medicine, 6(4), 291-296. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6302103/
  9. Neri, L., & Woznik, P. (n.d.). Citrulline — Health benefits, dosage, safety, side-effects, and more | Supplements. Examine. Retrieved from https://examine.com/supplements/citrulline/
  10. Johnson, S. (2017, November 20). L-Citrulline. FDA.report. Retrieved from https://fda.report/media/109619/FDA-Presentations-for-the-November-20-21--2017-Meeting-of-the-Pharmacy-Compounding-Advisory-Committee.pdf
  11. Gough, L.A., Sparks, S.A., McNaughton, L.R. et al. (2021). A critical review of citrulline malate supplementation and exercise performance. Eur J Appl Physiol, 121, 3283–3295. Retrieved from https://link.springer.com/article/10.1007/s00421-021-04774-6
  12. Dhaliwal, A. & Gupta, M. (2022, May 20). PDE5 Inhibitors. StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK549843/
Editorial Standards

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.

Kelly Brown MD, MBA
Kelly Brown MD, MBA

Dr. Kelly Brown is a board certified Urologist and fellowship trained in Andrology. She is an accomplished men’s health expert with a robust background in healthcare innovation, clinical medicine, and academic research. Dr. Brown was previously Medical Director of a male fertility startup where she lead strategy and design of their digital health platform, an innovative education and telehealth model for delivering expert male fertility care.

She completed her undergraduate studies at University of North Carolina at Chapel Hill (go Heels!) with a Bachelor of Science in Radiologic Science and a Minor in Chemistry. She took a position at University of California Los Angeles as a radiologic technologist in the department of Interventional Cardiology, further solidifying her passion for medicine. She also pursued the unique opportunity to lead departmental design and operational development at the Ronald Reagan UCLA Medical Center, sparking her passion for the business of healthcare.

Dr. Brown then went on to obtain her doctorate in medicine from the prestigious Northwestern University - Feinberg School of Medicine and Masters in Business Administration from Northwestern University - Kellogg School of Management, with a concentration in Healthcare Management. During her surgical residency in Urology at University of California San Francisco, she utilized her research year to focus on innovations in telemedicine and then served as chief resident with significant contributions to clinical quality improvement. Dr. Brown then completed her Andrology Fellowship at Medical College of Wisconsin, furthering her expertise in male fertility, microsurgery, and sexual function.

Her dedication to caring for patients with compassion, understanding, as well as a unique ability to make guys instantly comfortable discussing anything from sex to sperm makes her a renowned clinician. In addition, her passion for innovation in healthcare combined with her business acumen makes her a formidable leader in the field of men’s health.

Dr. Brown is an avid adventurer; summiting Mount Kilimanjaro in Tanzania (twice!) and hiking the incredible Torres del Paine Trek in Patagonia, Chile. She deeply appreciates new challenges and diverse cultures on her travels. She lives in Denver with her husband, two children, and beloved Bernese Mountain Dog. You can find Dr. Brown on LinkedIn for more information.

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