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L-Citrulline

Also known as Citrulline, Citrulline malate, L-Citrulline DL-malate

Amino acid named after watermelon (Citrullus) that the kidneys turn into arginine, so it raises blood arginine and nitric-oxide markers. Sold in two forms that are not interchangeable: pure L-citrulline, and citrulline malate, which is citrulline bound to malic acid, so a gram of it contains less citrulline. Most gym trials used citrulline malate: a meta-analysis of 8 studies found about 6% more repetitions before failure, while cycling and endurance trials were mostly negative. Blood-pressure findings are mixed: a 2018 meta-analysis found no effect, while small trials of pure L-citrulline in older, hypertensive or diabetic adults report lower aortic pressure and better artery function.

What trials found, in numbers

Summaries of published trial results for this compound, grouped by condition. In these tables every number is exactly as the researchers published it. The headline figures above show a simple average where several studies measured the same thing in the same unit, and say so; nothing else is calculated or converted.

How to read this table

Benefit: What the trial saw happen: whether the measured outcome moved in the helpful direction in that one study (the tag on each row: “Benefit seen”, “No clear benefit”, “Possible harm” or “Unclear”). It is a study result — not advice, and not a promise it will work for you.
Evidence: How strong the research behind that result is. A meta-analysis pools many studies (strongest); a systematic review collates them; an RCT tests against a control (placebo); observational studies only watch — they can suggest, not prove.
Effect size: How large the measured change was, exactly as the researchers published it. “No number reported” means the abstract gave no effect size — we never invent one.

In short: benefit is what was observed; evidence is how much you should trust the observation. A “Benefit seen” tag on a weak study counts for far less than the same tag on a meta-analysis.

Endurance (15 outcomes)

Outcome measured	What trials found	Effect size	People studied	Duration	Type of evidence	Study
Acute vasodilation and muscle blood flow (scarce, inconsistent evidence)	L-citrulline or citrulline malate showed an unclear effect on Acute vasodilation and muscle blood flow (scarce, inconsistent evidence) with no comparator reported.Unclear	no number reported	—	—	Systematic review · 2020	PMID 31977835
Exercise performance and recovery	L-citrulline or citrulline malate showed an unclear effect on Exercise performance and recovery with no comparator reported.Unclear	no number reported	—	—	Systematic review · 2020	PMID 31977835
Plasma citrulline, arginine and nitrate/nitrite concentrations	L-citrulline or citrulline malate improved Plasma citrulline, arginine and nitrate/nitrite concentrations with no comparator reported.Benefit seen	no number reported	—	—	Systematic review · 2020	PMID 31977835
Oxygen uptake (VO2), citrulline-alone group, before vs after 28 days	Citrulline (3000 mg twice daily) showed an unclear effect on Oxygen uptake (VO2), citrulline-alone group, before vs after 28 days from baseline (before-after within one group) (p = 0.04) (28 consecutive days). (p = 0.04)Unclear	no number reported	—	28 consecutive days	RCT · 2024	PMID 39417670
fatigue index (FI)	Citrulline-malate did not significantly improve fatigue index (FI) (p>0.05) compared with placebo; the difference versus placebo was not statistically established in 28. (p>0.05)No clear benefit	no number reported	28	—	RCT · 2021	PMID 31994989
mean watts	Citrulline-malate did not significantly improve mean watts (p>0.05) compared with placebo; the difference versus placebo was not statistically established in 28. (p>0.05)No clear benefit	no number reported	28	—	RCT · 2021	PMID 31994989
peak watts	Citrulline-malate did not significantly improve peak watts (p>0.05) compared with placebo; the difference versus placebo was not statistically established in 28. (p>0.05)No clear benefit	no number reported	28	—	RCT · 2021	PMID 31994989
time-to-exhaustion [TTE]	Citrulline-malate did not significantly improve time-to-exhaustion [TTE] (p>0.05) compared with placebo; the difference versus placebo was not statistically established in 28. (p>0.05)No clear benefit	no number reported	28	—	RCT · 2021	PMID 31994989
Total Work Completed (TWC)	Citrulline-malate did not significantly improve Total Work Completed (TWC) (p>0.05) compared with placebo; the difference versus placebo was not statistically established in 28. (p>0.05)No clear benefit	no number reported	28	—	RCT · 2021	PMID 31994989
Exercise heart rate (higher with citrulline malate)	Citrulline malate (12 g) showed an unclear effect on Exercise heart rate (higher with citrulline malate) compared with placebo in 10.Unclear	no number reported	10	—	RCT · 2016	PMID 26808848
Plasma citrulline concentration increase	Citrulline malate (12 g) improved Plasma citrulline concentration increase (8.8-fold; p ≤ 0.05) compared with placebo in 10. (p ≤ 0.05)Benefit seen	8.8-fold	10	—	RCT · 2016	PMID 26808848
Plasma glutamine concentration increase	Citrulline malate (12 g) improved Plasma glutamine concentration increase (1.3-fold; p ≤ 0.05) compared with placebo in 10. (p ≤ 0.05)Benefit seen	1.3-fold	10	—	RCT · 2016	PMID 26808848
Plasma ornithine concentration increase	Citrulline malate (12 g) improved Plasma ornithine concentration increase (3.9-fold; p ≤ 0.05) compared with placebo in 10. (p ≤ 0.05)Benefit seen	3.9-fold	10	—	RCT · 2016	PMID 26808848
Power fatigue index	Citrulline malate (12 g) did not significantly improve Power fatigue index (36 ± 16% CM vs. 28 ± 18% PL; p > 0.05) compared with placebo in 10. (p > 0.05)No clear benefit	36 ± 16% CM vs. 28 ± 18% PL	10	—	RCT · 2016	PMID 26808848
Time-to-exhaustion (TTE)	Citrulline malate (12 g) did not significantly improve Time-to-exhaustion (TTE) (120 ± 61 seconds CM vs. 113 ± 50 seconds PL; p > 0.05) compared with placebo in 10. (p > 0.05)No clear benefit	120 ± 61 seconds CM vs. 113 ± 50 seconds PL	10	—	RCT · 2016	PMID 26808848

Heart Health (22 outcomes)

Outcome measured	What trials found	Effect size	People studied	Duration	Type of evidence	Study
aortic diastolic blood pressure change	L-citrulline supplementation did not significantly improve aortic diastolic blood pressure change (0.26 mmHg; 95% CI - 2.27, 2.80 mmHg) with no comparator reported; the difference versus the comparator was not statistically established. (95% CI - 2.27, 2.80 mmHg)No clear benefit	0.26 mmHg	—	—	Meta-analysis · 2018	PMID 30284051
aortic systolic blood pressure change	L-citrulline supplementation did not significantly improve aortic systolic blood pressure change (0.22 mmHg; 95% CI - 4.81, 4.38 mmHg) with no comparator reported; the difference versus the comparator was not statistically established. (95% CI - 4.81, 4.38 mmHg)No clear benefit	0.22 mmHg	—	—	Meta-analysis · 2018	PMID 30284051
brachial diastolic blood pressure change	L-citrulline supplementation did not significantly improve brachial diastolic blood pressure change (- 1.56 mmHg; 95% CI - 4.32, 1.20 mmHg) with no comparator reported; the difference versus the comparator was not statistically established. (95% CI - 4.32, 1.20 mmHg)No clear benefit	- 1.56 mmHg	—	—	Meta-analysis · 2018	PMID 30284051
brachial systolic blood pressure change	L-citrulline supplementation did not significantly improve brachial systolic blood pressure change (0.28 mmHg; 95% CI - 2.87, 2.31 mmHg) with no comparator reported; the difference versus the comparator was not statistically established. (95% CI - 2.87, 2.31 mmHg)No clear benefit	0.28 mmHg	—	—	Meta-analysis · 2018

Strength (36 outcomes)

Outcome measured	What trials found	Effect size	People studied	Duration	Type of evidence	Study
Total number of repetitions performed before reaching voluntary muscular failure	Citrulline malate improved Total number of repetitions performed before reaching voluntary muscular failure (3 ± 5; 6.4 ± 7.9%; p = .022; 0.196) compared with placebo in 137. (p = .022)Benefit seen	3 ± 5	137	—	Meta-analysis · 2021	PMID 34010809
muscle mass	Citrulline supplementation (CIT) improved muscle mass compared with placebo in 250 participants.Benefit seen	no number reported	250 participants	—	Systematic review · 2020	PMID 31714265
muscle strength	Citrulline supplementation (CIT) improved muscle strength compared with placebo in 250 participants.Benefit seen	no number reported	250 participants	—	Systematic review · 2020	PMID 31714265
physical performance	Citrulline supplementation (CIT) improved physical performance compared with placebo in 250 participants.Benefit seen	no number reported	250 participants	—	Systematic review · 2020	PMID 31714265
upper muscle strength	Citrulline supplementation (CIT) combined with exercise improved upper muscle strength across mixed comparators in 250 participants.Benefit seen	no number reported	250 participants	—	Systematic review · 2020	PMID 31714265

Important: This page reflects observational, aggregate-only community reporting and independent published research. It is not medical advice, and it does not claim any compound treats, cures, or is effective for any condition. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or treatment.

Understand what people are taking.

L-Citrulline

What the research actually shows

The headline results, condition by condition

Strength

Why people look into L-Citrulline — and what they report

Where to get L-Citrulline (UK)

Endurance

Heart Health

Where the evidence is concentrated

Suggested uses (unproven)

Where the evidence is negative

What trials found, in numbers