L-citrulline is a naturally occurring amino acid involved in multiple bodily processes, particularly in circulation, energy production, and metabolic support. While it doesn't build proteins like other amino acids, it plays a key role in producing arginine, nitric oxide, and urea—all important for vascular function and cellular energy.

Available in both food and supplement form, L-citrulline may offer benefits for exercise performance, blood pressure, and blood sugar regulation.

What Are the Potential Benefits of L-Citrulline?

1. Exercise Performance and Recovery

L-citrulline may enhance physical performance by improving blood flow to muscles through nitric oxide production. This can help reduce muscle fatigue, boost endurance, and shorten recovery time after workouts.

  • Most studies use a single pre-workout dose of 3–9 grams, with some extending supplementation over seven days.

  • While early results are promising, research is mixed and more rigorous trials are needed.

2. Blood Pressure Support

Because nitric oxide relaxes blood vessels, L-citrulline has the potential to reduce blood pressure, especially in individuals with prehypertension or mild hypertension.

  • Some clinical trials report a modest reduction in systolic and diastolic blood pressure, but results have been inconsistent.

  • Further research is required to confirm how effective it truly is as a long-term treatment.

3. Blood Sugar and Metabolic Health

L-citrulline may improve insulin sensitivity and blood vessel health in people with high blood sugar or type 2 diabetes.

  • Small studies suggest it may lower blood glucose, reduce inflammation, and even improve cholesterol profiles.

  • Other research has not found significant benefits in insulin function, so results remain inconclusive.

How Much L-Citrulline Should You Take?

There is currently no official Recommended Daily Allowance (RDA) for L-citrulline. However, studies have used the following doses safely:

  • 3–6 grams per day for general cardiovascular or exercise benefits

  • 6–12 grams as a single pre-exercise dose

  • Up to 15 grams in one-time studies without major side effects

Note: L-citrulline hasn’t been studied in children or in people who are pregnant or breastfeeding. It’s best to consult a healthcare provider before use in these groups.

Best Dietary Sources of L-Citrulline

Watermelon (Citrullus lanatus)

This fruit is the richest natural source, containing 365 mg of L-citrulline per cup.

Other Possible Sources:

  • Cantaloupe

  • Cucumbers

  • Pumpkin

  • Squash

However, these foods contain significantly less citrulline than watermelon and have not been as well studied.

L-Citrulline Supplements: What to Know

L-citrulline is available as a capsule or powder supplement and comes in two main forms:

1. Pure L-Citrulline

  • Contains only the amino acid

  • Typically used for cardiovascular or metabolic health

2. Citrulline Malate

  • Combined with malic acid, which may help improve energy production and absorption

  • Popular in pre-workout formulas

  • Provides 566 mg of actual L-citrulline per 1,000 mg of citrulline malate

When choosing a supplement, look for third-party testing by organizations like:

  • NSF International

  • USP (United States Pharmacopeia)

  • ConsumerLab

These certifications help ensure purity, safety, and accurate labeling.

Are There Any Side Effects or Risks?

L-citrulline is generally well tolerated. In clinical studies, doses up to 6 grams per day for two months have been safely used. The most common side effects are:

  • Mild stomach discomfort

  • Occasional heartburn

Drug Interactions to Watch For

L-citrulline may interact with certain medications, especially those affecting blood pressure or circulation:

  • Antihypertensive medications: Could cause low blood pressure when combined

  • PDE-5 inhibitors (Viagra, Cialis): May intensify vasodilation, leading to lightheadedness or low BP

  • Always consult your provider if you're on cardiovascular medication or drugs that affect blood flow

A Quick Summary

L-citrulline is a non-essential amino acid that supports circulation, muscle performance, and metabolic health. It may improve exercise recovery, help manage blood pressure, and benefit those with blood sugar imbalances.

While more research is needed to confirm all potential benefits, it’s generally safe for healthy adults in moderate doses. If you're considering supplementation, especially for exercise or vascular health, talk with your healthcare provider to see if it's right for you.