L-citrulline benefits: what the research does and doesn't show

The evidence doesn't support L-citrulline as a treatment for erectile dysfunction, high blood pressure, or as a guaranteed exercise boost. What's actually been tested is narrower: a small improvement in high-intensity exercise performance across a dozen pooled trials, blood-pressure reductions specific to people who already have elevated blood pressure, and one small trial on mild erectile difficulty.

What the evidence doesn't support

It doesn't support L-citrulline as a treatment, cure or prevention for erectile dysfunction, hypertension or cardiovascular disease — no trial below tested it as a treatment for a diagnosed condition, and the one erectile-dysfunction trial's own authors describe citrulline as less effective than standard prescription treatment. It doesn't support a meaningful blood-pressure effect in people whose blood pressure is already normal — every positive blood-pressure result below came from adults already classified with prehypertension or hypertension. And it doesn't support a guaranteed strength or power benefit from a single dose: the pooled estimate across the meta-analysis below is a small effect, and the confidence interval for every individual study included still crossed the line of no effect at all.

What the trials found

A 2019 systematic review and meta-analysis pooled 12 studies (198 participants total) testing a single dose of citrulline — at least 3 g, given at least 30 minutes before high-intensity strength or power exercise such as bench-press repetitions or sprinting — against a placebo. The pooled result favored citrulline by a small margin (standardized mean difference 0.20, 95% CI 0.01-0.39, p=0.036): a real but modest effect, and one where every individual study's own confidence interval still crossed zero. The authors note the effect could matter to competitive athletes decided by small margins, but call for more research into which form, dose, sex and exercise type moderates the result.

A 2025 randomized, double-blind, placebo-controlled trial gave 33 resistance-trained men either 8 g/day of plain L-citrulline, 12 g/day of citrulline DL-malate, or a placebo, alongside a 6-week resistance-training program. Upper-body muscular endurance (repetitions to failure on bench press and incline press) improved significantly more in both citrulline groups than placebo; lower-body endurance showed only a non-significant trend. A blood marker of nitric-oxide production rose in both citrulline groups but not placebo. There was no meaningful difference between the plain L-citrulline group and the citrulline-malate group on any outcome. One of the study's authors owns the gym where the training sessions were run — a disclosed, non-financial conflict worth knowing about.

A 2010 randomized, double-blind, crossover trial gave 41 men a single 8 g dose of citrulline malate or a placebo before a bench-press training session. Repetitions completed increased significantly from the third set onward with citrulline malate, reaching 53% more repetitions than placebo by the final set, and muscle soreness 24 and 48 hours later was about 40% lower. The only side effect reported was stomach discomfort, in roughly 15% of participants.

A 2012 randomized, crossover trial gave 14 adults (11 women, 3 men) with prehypertension or stage-1 hypertension 6 g/day of L-citrulline/L-arginine from a watermelon extract, or a placebo, for 6 weeks each. Ankle and brachial blood pressure, and a measure of arterial stiffness (carotid augmentation index), were all significantly lower after the watermelon-extract period than after placebo. The trial didn't test whether the same effect shows up in people with normal blood pressure to begin with.

A 2017 review by the same research group summarizes the broader pattern across their own and other trials: L-citrulline reliably raises plasma arginine, but the downstream effect on nitric-oxide production and blood-vessel dilation is inconsistent, especially after a single acute dose. The blood-pressure-lowering effect is consistently seen in adults who already have prehypertension or hypertension, not in people with normal blood pressure, and chronic (multi-week) supplementation, not a single dose, is what's linked to improved exercise-related outcomes like skeletal-muscle oxygenation.

A 2011 single-blind, sequential trial gave 24 men with mild erectile dysfunction (an erection-hardness score of 3 out of 4) a placebo for one month and 1.5 g/day of L-citrulline for another month. The erection-hardness score improved from 3 to 4 (normal function) in 50% of the men on citrulline, compared with 8.3% on placebo (p<0.01), and monthly intercourse frequency rose from about 1.4 to 2.3. No adverse events were reported. The trial's own authors describe citrulline as less effective than PDE-5 inhibitor medication, at least in the short term, and call it a possible option specifically for men reluctant to take that medication — not a replacement for it. It's a small, single-blind trial in men with mild symptoms only, and we didn't find an independent replication.

Questions people ask

Is L-citrulline good for you?

The honest answer depends on what you're asking it to do. The use with the most consistent trial base is exercise performance, where the effect is real but small. The blood-pressure and erectile-dysfunction findings above come from far fewer, smaller trials.

What is L-citrulline good for?

Across the trials above: a small improvement in high-intensity exercise performance and muscular endurance, a blood-pressure reduction specific to people with already-elevated blood pressure, and improved erection hardness in men with mild erectile dysfunction in one small trial. None of that makes citrulline a treatment for a diagnosed condition.

Does L-citrulline increase blood flow?

It reliably raises plasma arginine, the building block for nitric oxide, but a 2017 review of this exact research found the downstream effect on blood flow itself is inconsistent, particularly after a single dose rather than weeks of use.

Is L-citrulline good for ED?

One small, single-blind trial found improved erection hardness in men with mild erectile dysfunction on 1.5 g/day for a month — its own authors describe it as less effective than prescription PDE-5 inhibitor medication. It hasn't been tested in men with moderate or severe erectile dysfunction, and we didn't find an independent replication of this specific trial.

Is L-citrulline good for blood pressure?

In the trials above, yes, specifically for adults already diagnosed with prehypertension or hypertension — not for people with normal blood pressure, where the effect hasn't been shown.

Is L-citrulline good for the heart?

No trial above measured a heart-disease outcome like heart attack or stroke. The blood-pressure and arterial-stiffness findings are measurements of cardiovascular risk factors, not evidence about disease outcomes themselves.

Is L-citrulline good for kidneys?

No trial above tested citrulline as a treatment for kidney disease. See who should not take L-citrulline for what the research does say about kidney function and citrulline dosing.

When to talk to a doctor

L-citrulline is not a treatment for erectile dysfunction, high blood pressure or any other diagnosed condition, and nothing above should stand in for a doctor's evaluation of any of those. If you have diagnosed hypertension, cardiovascular disease or erectile dysfunction, or take medication for any of them, talk to a doctor before adding L-citrulline or any new supplement.

Related reading: what is L-citrulline?, how much L-citrulline should you take a day?, and L-citrulline side effects.