L-Citrulline: Benefits, Citrulline Malate, Dosage And Safety

L-citrulline is an amino acid your kidneys convert into L-arginine, the raw material your blood vessels use to make nitric oxide. As a supplement, L-citrulline raises blood arginine more reliably than arginine itself does, which is why it shows up in pre-workouts and “blood flow” formulas. The evidence is real but modest: meta-analyses find small, inconsistent exercise benefits, a reduction in post-workout soreness and effort, and a modest drop in blood pressure in middle-aged and older adults. Typical doses are 3–6 g of L-citrulline or 6–8 g of citrulline malate.

Disclosure: nootropic.org/ may earn a commission from qualifying purchases made through links on this page, including as an Amazon Associate. This never affects which products we recommend. Learn more.

What Is L-Citrulline And How Does It Work?

L-citrulline is a non-essential amino acid. Your body makes it, and it is found in foods, most famously watermelon. It is not one of the amino acids used to build proteins. Its main job is as an intermediate in two cycles: the urea cycle in the liver and the arginine–nitric oxide cycle in blood vessels and other tissues.

The appeal as a supplement comes from a quirk of absorption. If you swallow L-arginine, a large share is broken down by the enzyme arginase in the gut and liver before it reaches circulation. L-citrulline is absorbed readily and then converted to arginine, largely in the kidneys. In a randomized crossover study of 20 healthy volunteers, one week of oral L-citrulline raised plasma arginine and the arginine-to-ADMA ratio (a marker of how much substrate is available to nitric oxide synthase), and increased urinary nitrate and cGMP, both downstream signals of nitric oxide activity.^[1] Notably, none of the treatments improved flow-mediated dilation, a direct test of artery function, in those healthy young people.

There is also a ceiling. In a dose-ranging study, single doses of 2, 5, 10 and 15 g were safe and well tolerated, but at the highest doses citrulline piled up in the blood while arginine rose less than expected, likely because the kidneys’ conversion capacity was saturated.^[2] More is not proportionally better.

A 2020 review in the Journal of Strength and Conditioning Research summed up the gap between theory and results: citrulline reliably raises blood citrulline, arginine and nitrate/nitrite, but evidence that it acutely improves blood vessel dilation or muscle blood flow is “scarce and inconsistent.”^[3]

L-Citrulline Vs Citrulline Malate (2:1)

Shoppers searching for “citrulline or citrulline malate” are really asking two questions: which form works, and how much citrulline is in each.

• L-citrulline is the pure amino acid. A 3 g scoop is 3 g of citrulline.
• Citrulline malate (also sold as L-citrulline DL-malate) binds citrulline to malic acid, an intermediate in the cell’s energy cycle. A “2:1” product is labeled as two parts citrulline to one part malate. If that ratio is by weight, 8 g of citrulline malate 2:1 delivers about 5.3 g of citrulline. A 1:1 product delivers only about half its weight as citrulline.

Most of the strength-training studies used citrulline malate, typically 8 g taken about an hour before exercise.^[6] Blood pressure and vascular studies more often used plain L-citrulline. Whether malate adds anything on its own has not been settled in head-to-head trials, so the practical rule is simple: compare products by citrulline content, not by total grams.

Form	Citrulline Per 8 g (Approx.)	Where It Was Studied	Notes
L-citrulline	8 g	Blood pressure, vascular function, pharmacokinetics	Most direct; easy to dose by weight
Citrulline malate 2:1	About 5.3 g	Resistance training, soreness	The form in most pre-workout trials
Citrulline malate 1:1	About 4 g	Few trials	Less citrulline per gram; check labels

L-Citrulline Benefits: What The Research Shows

Exercise Performance (Evidence: Limited)

This is the main reason people buy citrulline, and the evidence is weaker than marketing suggests. The largest analysis to date, a 2026 three-level meta-analysis of 30 randomized trials (644 participants), found citrulline malate was associated with a small improvement in overall exercise performance (Hedges’ g = 0.16). Prediction intervals were wide, the pooled effect on perceived exertion was not significant, and the certainty of evidence was rated low to very low. Acute (single-dose) protocols looked more stable than longer supplementation, but subgroup findings did not hold up in sensitivity analyses.^[4]

Narrower meta-analyses are less encouraging still:

• Strength: A meta-analysis of four trials in resistance-trained adults found no overall effect of citrulline malate on muscle strength (SMD 0.13, not significant) for upper or lower body.^[5]
• Endurance: A 2023 meta-analysis found no significant benefit of acute citrulline on time to exhaustion or time-trial performance in young, healthy adults, while noting the evidence base is small.^[7]

Individual trials can look impressive. In a frequently cited crossover study of 41 men, 8 g of citrulline malate taken before a bench-press session increased repetitions to fatigue, with the biggest gains in later sets, and cut muscle soreness at 24 and 48 hours by about 40%.^[8] Later studies have not consistently reproduced effects that large, which is why pooled estimates are small.

Muscle Soreness And Perceived Effort (Evidence: Moderate)

The more consistent signal is in how exercise feels. A meta-analysis of 13 studies (206 participants), in which the most common dose was 8 g of citrulline malate, found citrulline significantly reduced ratings of perceived exertion and muscle soreness 24 hours after exercise. It did not lower blood lactate, and effects on soreness at 48 and 72 hours were not significant.^[6] The 2026 analysis did not find a significant pooled effect on exertion, so treat this as a modest, plausible benefit rather than a sure thing.^[4]

Blood Pressure (Evidence: Moderate)

A 2025 meta-analysis of 15 randomized trials (415 participants) in middle-aged and older adults found L-citrulline supplementation and watermelon intake together lowered systolic blood pressure by about 4 mmHg on average, with a smaller drop in diastolic pressure. Combining citrulline with arginine appeared more effective than either citrulline or watermelon alone.^[9] A separate 2022 meta-analysis found that longer-term citrulline or watermelon intake may improve vascular function, while single doses did not change post-meal vascular measures.^[10]

A 4 mmHg reduction is in the range of some lifestyle changes, but trials were small and short. Citrulline is not a substitute for prescribed blood pressure treatment, and anyone with hypertension should talk with their doctor before adding it.

Erectile Function (Evidence: Preliminary)

Because erections depend on nitric oxide signaling, citrulline has been tested in mild erectile dysfunction. In a small single-blind study, 24 men with mild ED took a placebo for one month, then 1.5 g a day of L-citrulline for one month. Erection hardness improved to normal in 12 of 24 men on citrulline versus 2 of 24 on placebo, with no adverse events. The authors noted citrulline was less effective than PDE5 inhibitor drugs.^[11] The study was small, short and not fully blinded. ED can be an early sign of cardiovascular disease, so it warrants a medical evaluation rather than self-treatment.

Brain And Cognition (Evidence: None In Humans)

Citrulline is sometimes marketed for “cerebral blood flow” or focus. We could not find controlled human trials showing that citrulline supplements improve cognition or brain blood flow in healthy people. If brain performance is your goal, ingredients with actual human cognitive data, such as creatine, caffeine or L-theanine, are better places to start. See our best nootropics guide for a ranked overview.

L-Citrulline Dosage: Studied Doses

Purpose	Dose	Duration	Study
Resistance exercise performance, soreness	8 g citrulline malate, about 1 hour before training	Single dose	Pérez-Guisado 2010; most common dose in meta-analysis[6][8]
Raising plasma arginine	2–15 g L-citrulline (single doses)	Single dose	Moinard 2008[2]
Nitric oxide markers	Daily L-citrulline (several regimens)	1 week	Schwedhelm 2008[1]
Mild erectile dysfunction	1.5 g L-citrulline daily	1 month	Cormio 2011[11]
Blood pressure, older adults	Varied across trials	Weeks	Luo 2025 meta-analysis[9]

In practice:

• L-citrulline: 3–6 g a day, either before exercise or split through the day for vascular goals.
• Citrulline malate 2:1: 6–8 g about 60 minutes before training, matching most exercise studies.
• Upper range: Single doses up to 15 g were tolerated in a short study, but arginine conversion plateaus at high doses, so there is little reason to exceed about 10 g.^[2]

Forms And What To Look For

• Powder vs capsules or tablets: Citrulline doses are measured in grams. A 3 g dose is five 650 mg capsules, so many people use powder for 6–8 g doses. Capsules and tablets suit lower or split doses.
• Check the ratio: “Citrulline malate” without a ratio, or a 1:1 ratio, means less citrulline per scoop than 2:1.
• Beware proprietary blends: Many pre-workouts list citrulline inside a blend without a gram amount, often well below studied doses.
• Testing: Choose brands that publish third-party or batch testing (a certificate of analysis).
• Citrulline hydrochloride and “citrulline complex” products have little or no direct research; plain L-citrulline or 2:1 malate are the studied forms.

Side Effects And Safety

L-citrulline is one of the better-tolerated sports supplements. In the dose-ranging study, single doses up to 15 g were described as safe and well tolerated in healthy men, with no effect on insulin or growth hormone.^[2] In the bench-press trial, the only reported side effect was stomach discomfort in about 15% of participants taking 8 g of citrulline malate.^[8] No adverse events were reported in the small erectile function study.^[11]

Long-term safety data beyond a few months are limited. For more on what to watch for with any supplement, see our nootropic side effects guide.

Drug Interactions And Who Should Avoid It

Because citrulline can lower blood pressure in some people,^[9] the main concerns are additive effects with other drugs that do the same:

• Nitrates (such as nitroglycerin or isosorbide) used for chest pain: these act on the same nitric oxide pathway; combining them with nitric oxide boosters could cause excessive drops in blood pressure.
• PDE5 inhibitors (sildenafil, tadalafil and similar drugs): these also amplify nitric oxide signaling. Do not combine without your doctor’s input.
• Blood pressure medications: additive lowering is possible; monitor and discuss with your prescriber.

People with low blood pressure, kidney disease, inherited urea cycle disorders, and those who are pregnant or breastfeeding should check with a clinician first, as research in these groups is lacking.

How L-Citrulline Pairs With Other Supplements

• Creatine: The two are often stacked in pre-workouts. They work by different mechanisms, and creatine has far stronger performance evidence on its own.
• Agmatine: Sometimes paired with citrulline in “pump” products. Agmatine has no published human exercise trials, so citrulline is the better-supported of the two for exercise.
• Arginine: The blood pressure meta-analysis suggested citrulline plus arginine may beat either alone, though this is based on subgroup comparisons.^[9]
• Caffeine: Common in pre-workouts; adds alertness but may raise blood pressure acutely in some people. See our caffeine guide.

For brain-focused stacking ideas, see our nootropic stacks guide.

Where To Buy L-Citrulline Supplements

We point readers to Nootropics Depot for single-ingredient amino acids because the company publishes certificates of analysis and offers both capsules and a 2:1 malate powder. Read our Nootropics Depot review for background on their testing. On Amazon, buy only from listings marked “Sold by Nootropics Depot,” since third-party resellers are not authorized.

L-Citrulline FAQs

What Is L-Citrulline Malate?

It is L-citrulline bound to malic acid. A 2:1 product is about two parts citrulline to one part malate, so 8 g provides roughly 5 g of citrulline. It is the form used in most strength-training studies.^[6]

Is L-Citrulline Better Than L-Arginine?

For raising blood arginine, yes. Oral arginine is heavily broken down before reaching circulation, while oral citrulline raised plasma arginine and nitric oxide markers in a controlled study.^[1]

How Much Citrulline Malate Should I Take?

Most exercise studies used 8 g of citrulline malate about an hour before training.^[6] If you use plain L-citrulline, 3–6 g is the usual range.

Does L-Citrulline Lower Blood Pressure?

Modestly, in some people. Across 15 trials in middle-aged and older adults, systolic blood pressure dropped by about 4 mmHg on average.^[9] Do not use it in place of prescribed treatment.

Can I Take L-Citrulline With Viagra?

Not without your doctor’s approval. Both act on nitric oxide signaling and both can lower blood pressure. The same caution applies to nitrate heart medications.

Is Citrulline Malate Better Than Creatine?

No. Creatine has much stronger and more consistent evidence for strength and power. Citrulline’s pooled effect on performance is small.^[4] They can be taken together.

Does L-Citrulline Work As A Nootropic?

There is no good human evidence that it improves cognition. Browse our ingredient library for compounds with actual cognitive trials.

References

1. Schwedhelm et al. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. British Journal of Clinical Pharmacology. 2008;65(1):51-59. PubMed
2. Moinard et al. Dose-ranging effects of citrulline administration on plasma amino acids and hormonal patterns in healthy subjects: the Citrudose pharmacokinetic study. British Journal of Nutrition. 2008;99(4):855-862. PubMed
3. Gonzalez et al. Effects of citrulline supplementation on exercise performance in humans: a review of the current literature. Journal of Strength and Conditioning Research. 2020;34(5):1480-1495. PubMed
4. Wang et al. Effects of citrulline malate supplementation on exercise performance: a systematic review and three-level meta-analysis. Nutrients. 2026;18(12). PubMed
5. Aguiar et al. Effects of citrulline malate supplementation on muscle strength in resistance-trained adults: a systematic review and meta-analysis of randomized controlled trials. Journal of Dietary Supplements. 2022;19(6):772-790. PubMed
6. Rhim et al. Effect of citrulline on post-exercise rating of perceived exertion, muscle soreness, and blood lactate levels: a systematic review and meta-analysis. Journal of Sport and Health Science. 2020;9(6):553-561. PubMed
7. Harnden et al. Effects of citrulline on endurance performance in young healthy adults: a systematic review and meta-analysis. Journal of the International Society of Sports Nutrition. 2023;20(1):2209056. PubMed
8. Pérez-Guisado et al. Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness. Journal of Strength and Conditioning Research. 2010;24(5):1215-1222. PubMed
9. Luo et al. Does L-citrulline supplementation and watermelon intake reduce blood pressure in middle-aged and older adults? A systematic review and meta-analysis of randomized controlled trials. Clinical Nutrition ESPEN. 2025;69:653-664. PubMed
10. Smeets et al. Effects of L-citrulline supplementation and watermelon consumption on longer-term and postprandial vascular function and cardiometabolic risk markers: a meta-analysis of randomized controlled trials in adults. British Journal of Nutrition. 2022;128(9):1758-1770. PubMed
11. Cormio et al. Oral L-citrulline supplementation improves erection hardness in men with mild erectile dysfunction. Urology. 2011;77(1):119-122. PubMed