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L-Citrulline

supporting nitric oxide production and vasodilation

amino-acid
Human trial evidenceTraditional useInteraction riskNeeds more research

NO precursor for circulation, exercise, and erectile function.

L-Citrulline is a non-essential amino acid that plays a role in the urea cycle, a process that removes ammonia from the body. It is also a precursor to L-arginine, another amino acid, which is then converted into nitric oxide. Nitric oxide is a vasodilator, meaning it helps to relax and widen blood vessels. This vasodilation effect is thought to be the basis for many of L-Citrulline's potential applications, particularly in areas related to cardiovascular health and exercise performance. While L-Citrulline is naturally found in some foods, such as watermelon, it is also available as a dietary supplement.

Quick answer

What it is: L-Citrulline is a non-essential amino acid that plays a role in the urea cycle, a process that removes ammonia from the body.

May support:Hypertension, High Blood Pressure, Erectile Dysfunction, Atherosclerosis

Evidence Summary

As no specific PubMed studies were provided, the current understanding of L-Citrulline's mechanisms and potential benefits is based on established biochemical pathways and general scientific consensus. Without direct evidence, claims regarding efficacy remain theoretical or based on indirect observations.

Last reviewed · Jun 2026

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Why It Works

Converts to arginine; sustained NO elevation.

How it works in more detail

Upon ingestion, L-Citrulline is absorbed and transported to the kidneys, where it is converted to L-arginine. This conversion bypasses hepatic metabolism, which can degrade L-arginine, making L-Citrulline a more effective way to increase plasma L-arginine levels. L-arginine is then used by endothelial nitric oxide synthase (eNOS) to produce nitric oxide (NO). NO acts as a signaling molecule, promoting the relaxation of vascular smooth muscle cells, leading to vasodilation and improved blood flow. This pathway is crucial for various physiological processes, including blood pressure regulation and oxygen delivery to tissues.

How to use

Always consult a qualified clinician.

Editorial guidance

Suggested dosage
3–8 g/day
Research dosage range
Research studies have explored a range of dosages, typically from 3 to 10 grams per day, depending on the specific outcome being investigated.
Typical onset
The effects of L-Citrulline on nitric oxide levels and blood flow may begin within 30-60 minutes after ingestion, with peak effects potentially observed within 1-2 hours.
Typical forms
capsule, powder
Quality markers
Look for products that are third-party tested for purity and potency. Ensure the label clearly states 'L-Citrulline' or 'Citrulline Malate' (if applicable) and the dosage per serving. Avoid products with excessive fillers or artificial ingredients.
Medication interactions
  • nitrates
  • blood pressure medications
  • erectile dysfunction medications
Avoid if
  • taking nitrates for heart conditions
  • taking erectile dysfunction medications

Community tips

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Suggested dosage

3–8 g/day

General guidance — discuss specifics with a clinician.

Active medicinal compounds

L-Citrulline

Traditional use

L-Citrulline itself does not have a history of traditional use as a standalone remedy. However, foods rich in L-Citrulline, such as watermelon, have been consumed for centuries and are recognized for their hydrating and nutritional properties.

Safety

Safety warnings

May lower BP.

Avoid if

  • taking nitrates for heart conditions
  • taking erectile dysfunction medications

Medication interactions

  • nitrates
  • blood pressure medications
  • erectile dysfunction medications

Reported side effects

  • mild gastrointestinal discomfort

General guidance — discuss specifics with a clinician.

Evidence ecosystem

Scientific literature, clinical guidance, government sources, ongoing research, traditional use, and lived experience — grouped by source type and quality.

Overall grade

As no specific PubMed studies were provided, the current understanding of L-Citrulline's mechanisms and potential benefits is based on established biochemical pathways and general scientific consensus. Without direct evidence, claims regarding efficacy remain theoretical or based on indirect observations.

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Observational Studies(1)

Cohort, case-control, and cross-sectional human studies.

Moderate Quality

  • Sexual Performance Anxiety.

    Pyke RE · Sexual medicine reviews · 2020

    Sexual performance anxiety (SPA) is one of the most prevalent sexual complaints; yet, no diagnosis is recognized for either gender. Thus, research into treatment has been minimal. Review the prevalence of SPA and its relation to sexual dysfunctions and anxiety disorders. Compare SPA to (non-sexual) performance anxiety and social anxiety (PA/SA). Apply pharmacologic principles to the known properties of drugs and phytotherapies to hypothesize treatments for SPA. Review SPA and PA/SA through PubMed searches for relevant literature from 2000 to 2018. Prevalence was estimated using population-representative surveys. For treatment results, controlled clinical trial results were prioritized over open-label trial results. SPA affects 9-25% of men and contributes to premature ejaculation and psychogenic erectile dysfunction (ED). SPA affects 6-16% of women and severely inhibits sexual desire. Cognitive behavior therapy and mindfulness meditation training have been proven effective for

    Observational StudyPubMedLow Quality

Animal Studies(1)

Preclinical animal research — not a substitute for human evidence.

Low Quality

  • Safety and efficacy of daily Revactin(®) in men with erectile dysfunction: a 3-month pilot study.

    Nguyen S, Rajfer J, Shaheen M · Translational andrology and urology · 2018

    The earliest sign of an ongoing change in a man's erectile function (EF) is the increase in his refractory period. This is due to the onset of an aging related apoptosis of the corporal smooth muscle cells (CSMC) as a result of oxidative stress (ROS) within the CSMC itself. In response, the CSMC begin to upregulate the inducible nitric oxide synthase (iNOS) enzyme presumably to achieve high levels of nitric oxide (NO) used to combat ROS. Treatment of aged rats for 2 months with the nutraceutical Revactin®, known to stimulate the iNOS-NO-cGMP pathway in CSMC, resulted in (I) an increase in CSMC content with a decrease in corporal fibrosis, (II) decrease in systemic ROS, and (III) improvement in EF. To determine whether Revactin® could be used in the clinical setting, a pilot safety study was conducted. Fifty-four middle aged men (mean age 57.8±10.7; range, 33-77 years) were recruited for this safety study. Patients were given Revactin® twice daily (total daily dose

    Animal StudyPubMedLow Quality

Limitations: The primary limitation is the absence of specific, peer-reviewed PubMed studies to support direct claims of efficacy or safety for L-Citrulline in this context. Any potential benefits are inferred from its known metabolic pathways rather than direct clinical trial data.

This page is educational. Statements use phrases like "may support" and "has been studied for"because no remedy here is approved to cure, treat, or reverse any condition. Discussion happens on the ailment pages — community statistics here are derived from those reports. Always consult a qualified clinician.

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