L-citrulline is a substance called a non-essential amino acid. Your kidneys change L-citrulline into another amino acid called L-arginine and a chemical called nitric oxide.

These compounds are important to your heart and blood vessel health. They may also boost your immune system.

Why do people take L-citrulline?

L-citrulline boosts nitric oxide production in the body. Nitric oxide helps your arteries relax and work better, which improves blood flow throughout your body. This may be helpful for treating or preventing some diseases.

Ther is some evidence to suggest the supplement could possibly help lower blood pressure in people with prehypertension. This is an early warning sign for high blood pressure. It means you have a slightly raised blood pressure reading of 120/80 to 139/89. Prehypertension raises your risk for high blood pressure and heart disease.

L-citrulline supplements may ease symptoms of mild-to-moderate erectile dysfunction (ED). Scientists say L-citrulline does not work as well as ED drugs such as Viagra. However, it appears to be a safe option.

Animal studies suggest L-citrulline might also help people with blood vessel problems such as slow wound healing due to diabetes.

Other animal research says L-citrulline might improve muscle protein levels and prevent malnourishment in the elderly.

The animal research also suggests L-citrulline may help treat intestinal problems, including:

Certain genetic disorders and health conditions such as liver disease may be helped by L-citrulline supplements.

Early human studies done also hint that L-citrulline may be helpful for Parkinson's disease and certain dementias.

Some people also take L-citrulline to build muscles and improve athletic performance. But research shows it does not help well-trained athletes perform or exercise better.

The supplement usually comes in powder form. The suggested dosage for L-citrulline depends on what disease you are trying to treat or prevent, but is sometimes used up to 9 grams daily, divided throughout the day. However, optimal doses of L-citrulline have not been set for any condition. Quality and active ingredients in supplements may vary widely. This makes it hard to set a standard dose.


Can you get L-citrulline naturally from foods?

Yes, watermelon contains L-citrulline.

What are the risks of taking L-citrulline?

There are no reported side effects of L-citrulline.

However, the supplement may affect the way certain drugs work in your body. Do not take this supplement if you are taking:

Combining L-citrulline with those drugs may cause a dangerous drop in blood pressure.

You should also be careful when taking L-citrulline if you take any type of blood pressure medicine.

Do not use L-citrulline if you are pregnant or breastfeeding.

Always tell your doctor about any supplements you are taking. That way, your doctor can check on any potential side effects or interactions with any medications.

The U.S. Food and Drug Administration (FDA) does regulate dietary supplements; however, it treats them like foods rather than medications.

WebMD Medical Reference Reviewed by Melinda Ratini, DO, MS on September 24, 2019



News releases, National Standard Database: "L-Citrulline May Lower Blood Pressure," "Watermelon and Viagra."

Venes, D., editor, Taber's Cyclopedic Medical Dictionary, 19th edition. F.A. Davis Company, 2001.

Cormio, L. Urology, January 2011.

Smith, H. The Journal of Thoracic and Cardiovascular Surgery, July 2006.

Sureda, A. Medicine and Sport Science, 2013.

National Medicines Comprehensive Medicines web site. "L-Citrulline Monograph."

DiPetrio, N. Atherosclerosis, Nov. 8, 2012.

Osowska, S. American Journal of Physiology, Endocrinology, and Metabolism, 2006.

Curis, E. Amino Acids, 2005.

Carpenter, T.O.  New England Journal of Medicine, 1985.

Jesse, S. CNS Neuroscience and Therapeutics, June 2009.

Tremblay, G.C. New England Journal of Medicine, 1975.

Mandel H. Journal of Inherited Metabolic Disease, 2005.

Diego M. C., Zhao-Jun Liu, Omaida C. V. Oxygen: Implications of Wound Healing, 2012

© 2019 WebMD, LLC. All rights reserved.