Citrulline

Also known as: L-Citrulline, Citrulline Malate, CM, L-CIT

Evidence under review. — Not yet rated

Amino acid that boosts nitric oxide, supports blood flow, and may improve physical performance in older adults.

What it does

Citrulline is a naturally occurring amino acid found in watermelon and produced in the body as part of the urea cycle. It raises nitric oxide levels, which relaxes and widens blood vessels —...
Evidence quality

Evidence base hasn't been formally rated yet. See research below.
Clinical dose

3000-8000 mg daily based on study doses
Found in

IM8 Daily Ultimate Essentials Pro, 1.M.R OG Pre-Workout Formula, Nutricost Nitric Oxide Booster Capsules and 17 more

What the Science Says

Citrulline is a naturally occurring amino acid found in watermelon and produced in the body as part of the urea cycle. It raises nitric oxide levels, which relaxes and widens blood vessels — improving circulation and reducing blood pressure in people with elevated readings. Clinical trials show it can improve lower-limb physical function in older adults when combined with exercise, and may benefit vascular health, particularly in those with high-normal blood pressure.

What It Doesn't Do

Won't meaningfully boost aerobic or anaerobic exercise performance in already-trained adults at typical doses. Not a proven muscle-builder on its own. No strong evidence it helps healthy people with normal blood pressure. Acute single-dose supplementation before a workout is unlikely to make a noticeable difference.

Evidence-Based Benefits

Improves blood vessel flexibility and flow in adults with high-normal blood pressure after 12 weeks.

Moderate Evidence

Effective at: 3000 mg/day

Supporting studies (click to view on PubMed):

PMID 42142423

Improves lower-body strength and sit-to-stand performance in older women when combined with exercise.

Weak Evidence

Effective at: 3000 mg/day

Supporting studies (click to view on PubMed):

PMID 42162613

Watermelon (a natural citrulline source) may reduce ambulatory blood pressure in adults with elevated readings.

Weak Evidence

Effective at: No established dose from provided studies

Supporting studies (click to view on PubMed):

PMID 41097150

Reduces pancreatic oxidative stress and inflammation markers in animal models of metabolic syndrome.

Weak Evidence

Effective at: 200–800 mg/kg in animal models (human equivalent not established)

Supporting studies (click to view on PubMed):

PMID 42170986

Absorption & Bioavailability

Good — citrulline is better absorbed orally than arginine and is efficiently converted to arginine in the kidneys, raising plasma arginine and nitric oxide levels more reliably than arginine supplementation itself.

Red Flags to Watch For

Most vascular benefits appear only in people with elevated or high-normal blood pressure — if your BP is normal, don't expect the same results.
Many products use citrulline malate (combined with malic acid) rather than pure L-citrulline; doses listed on labels may not reflect actual citrulline content.
Acute pre-workout dosing at common commercial amounts showed no significant performance benefit in trained men — chronic use may be needed.
High-dose citrulline in the context of urea cycle disorders can contribute to DNA damage in lab studies — not a concern at supplement doses in healthy people, but worth noting for those with metabolic conditions.

Supplement

Mostly Legit

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Frequently Asked Questions

What does Citrulline do?

Amino acid that boosts nitric oxide, supports blood flow, and may improve physical performance in older adults.

What is the effective dose of Citrulline?

3000-8000 mg daily based on study doses

Is Citrulline safe?

Most vascular benefits appear only in people with elevated or high-normal blood pressure — if your BP is normal, don't expect the same results.

What doesn't Citrulline do?

Won't meaningfully boost aerobic or anaerobic exercise performance in already-trained adults at typical doses.

Research Sources

PubMed
NIH DSLD

This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-06-01