Does L-citrulline help with blood pressure? What the research does and doesn't show

The evidence doesn't support L-citrulline as a treatment for high blood pressure, and it hasn't been shown to lower blood pressure in people whose readings are already normal. What a 2025 meta-analysis of 15 trials and several individual studies below found is a modest reduction specifically in middle-aged and older adults with elevated blood pressure to begin with — a risk-factor measurement, not a disease outcome.

What the evidence doesn't support

No trial below tested L-citrulline as a treatment, cure or prevention for hypertension or cardiovascular disease — every trial measured blood pressure as a number, over weeks, not a diagnosed condition managed over years. None of the trials found a meaningful blood-pressure effect in people with normal blood pressure to start; every positive result came from adults already classified with prehypertension, hypertension, or an existing diagnosis. And the size of the average effect found — a few millimeters of mercury — is smaller than what prescription blood-pressure medication typically achieves, a comparison the trials themselves don't make but is worth having in mind.

What the trials found

A 2025 systematic review and meta-analysis pooled 15 randomized controlled trials (24 datasets, 415 participants) testing L-citrulline supplementation or watermelon intake against placebo in middle-aged and elderly adults. Averaged across trials, citrulline/watermelon lowered systolic blood pressure by about 4 mmHg (95% CI -6.54 to -1.50, p=0.002) and diastolic blood pressure by about 2.5 mmHg (95% CI -4.27 to -0.81, p=0.004). A subgroup of trials that combined citrulline with L-arginine showed a larger average reduction (systolic -10.44 mmHg, diastolic -4.86 mmHg) than citrulline or watermelon alone — the authors call the combined approach more effective, but that subgroup is a smaller slice of the pooled trials.

A 2024 randomized, placebo-controlled trial gave 22 hypertensive postmenopausal women 10 g/day of L-citrulline or placebo for 4 weeks. Versus placebo, citrulline significantly improved a measure of blood-vessel function (flow-mediated dilation), reduced resting aortic systolic blood pressure, and improved blood flow and muscle oxygenation during handgrip exercise. It's a small trial in a specific population — postmenopausal women with diagnosed hypertension — not a general finding.

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 were all significantly lower after the watermelon-extract period than after placebo. The trial didn't test people with normal blood pressure.

A 2017 review by a research group active in this area describes the overall pattern: a single dose of citrulline reliably raises blood arginine but has an inconsistent effect on blood flow itself, especially acutely. The blood-pressure-lowering effect shows up specifically in adults who already have prehypertension or hypertension across the trials the review covers — not in people with normal blood pressure — and depends on several weeks of use, not a single dose.

What hasn't been shown

No trial above measured a hard cardiovascular outcome like heart attack or stroke — every finding is a blood-pressure or arterial-stiffness number, which is a risk factor, not a disease event. No trial tested L-citrulline in people with normal blood pressure and found an effect; the research specifically doesn't support using it to lower blood pressure that's already in a normal range. And no trial tested L-citrulline against, or alongside, a prescription blood-pressure medication — a combination worth flagging to a doctor given the shared mechanism, covered in L-citrulline and medications: what to check.

Questions people ask

Does L-citrulline lower blood pressure?

In adults who already have elevated blood pressure, a 2025 meta-analysis of 15 trials found an average reduction of about 4 mmHg systolic and 2.5 mmHg diastolic. It hasn't been shown to lower blood pressure that's already normal.

Does L-citrulline raise blood pressure?

None of the trials reviewed here found a blood-pressure increase from L-citrulline; the direction of every finding was a decrease or no significant change.

How much L-citrulline is needed to affect blood pressure?

The trials with a positive finding used 6-10 g/day for 4-6 weeks, in adults with existing prehypertension or hypertension. The pooled meta-analysis covered a range of doses and durations across its 15 trials rather than one fixed protocol.

Is citrulline malate or plain L-citrulline better for blood pressure?

The blood-pressure trials above used plain L-citrulline or watermelon-extract citrulline/arginine, not citrulline malate specifically. We didn't find a trial comparing the two forms for this outcome.

Is L-citrulline better than L-arginine for blood pressure?

The 2025 meta-analysis found a larger average reduction in the subgroup of trials that combined citrulline with L-arginine than in trials using citrulline or watermelon alone — the two together, not one replacing the other, is what showed the bigger effect in the pooled data.

When to talk to a doctor

L-citrulline is not a treatment for high blood pressure, and nothing above should stand in for a doctor's monitoring and treatment of it. If you have diagnosed hypertension or take blood-pressure medication, talk to a doctor before adding L-citrulline — the effect sizes above are real but modest, and the interaction with blood-pressure medication hasn't been tested.

Related reading: L-citrulline benefits: what the research does and doesn't show and L-citrulline and medications: what to check.