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Moderate evidencePhysical performance

L-Citrulline

Citrulline bypasses the gut-and-liver breakdown that cripples oral arginine, making it the more effective nitric oxide precursor. Meta-analyses show a small but real increase in resistance-training repetitions and reduced post-exercise soreness — modest, but among the better-supported pre-workout ingredients.

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What the science says

  • Increasing resistance-training volume Moderate evidence

    Vårvik's 2021 systematic review and meta-analysis found acute citrulline malate increased total repetitions performed during resistance training versus placebo, though the pooled effect was small (roughly one to two extra reps across multiple sets). Effects were more consistent for upper-body, multiple-set-to-failure protocols.

  • Reducing post-exercise muscle soreness Moderate evidence

    Rhim's 2020 meta-analysis found citrulline supplementation significantly reduced muscle soreness at 24 and 48 hours post-exercise, and reduced rating of perceived exertion, while having no significant effect on blood lactate. The soreness effect is consistent across trials but modest in size.

  • Lowering blood pressure and improving vascular function Moderate evidence

    Citrulline raises plasma arginine and nitric oxide availability more effectively than equivalent doses of arginine, and randomised trials report small reductions in blood pressure and improvements in endothelial function, particularly in older or hypertensive adults. Note that one widely cited citrulline blood-pressure meta-analysis was retracted, so treat the pooled numbers with caution.

  • Endurance performance Limited evidence

    Endurance trials are mixed, with many null results for time-trial and time-to-exhaustion outcomes. Any benefit appears smaller and less reliable than the resistance-training effect.

Dosage & safety

Studied dose6-8 g of citrulline malate (roughly 3.5-4.5 g pure L-citrulline) taken 60 minutes pre-exercise is the standard acute performance protocol. Cardiovascular trials use 3-6 g/day of pure L-citrulline for 2-8 weeks. Note that citrulline malate is typically a 2:1 blend, so a "6 g" label supplies about 4 g of actual citrulline — and some published effects may partly reflect the malate.
SafetyVery well tolerated; unlike arginine, doses up to 15 g rarely cause GI distress. Blood-pressure-lowering effect can be additive with antihypertensives, nitrates and PDE5 inhibitors such as sildenafil — do not combine without medical advice. Insufficient data in pregnancy and breastfeeding. Not prohibited by WADA. Caution in people with kidney disease given increased nitrogen handling.

How to take it

Timing60 minutes before exercise for the performance protocol; for blood pressure, timing does not matter.
With food?With or without food; unlike arginine it does not need a meal to be tolerated.
Worth knowingCitrulline malate is usually a 2:1 blend, so a 6 g scoop is only about 4 g of actual citrulline — check which one the label is counting.

Interactions

With medications

  • nitrates and PDE5 inhibitors such as sildenafil

    Additive nitric oxide-mediated vasodilation, with a real risk of hypotension. do not combine without medical advice

  • antihypertensives

    Citrulline lowers blood pressure modestly, adding to your medication's effect. monitor blood pressure and tell your prescriber

With other supplements

  • beetroot or dietary nitrate

    Both raise nitric oxide by different routes, so blood pressure effects add. fine for most people, but do not stack them if you already run low

  • L-arginine

    Redundant — citrulline is the more effective way to raise plasma arginine. take one, not both

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does citrulline malate improve workout performance?

Yes, a little — the evidence is moderate. A 2021 meta-analysis found citrulline malate increased resistance-training repetitions, by roughly one to two extra reps across multiple sets.

How much citrulline should I take before a workout?

The standard protocol is 6–8 g of citrulline malate, about 3.5–4.5 g of pure L-citrulline, 60 minutes before exercise. Check the label, since a 6 g scoop of 2:1 citrulline malate is only about 4 g of citrulline.

Does L-citrulline reduce muscle soreness?

The evidence is moderate: a 2020 meta-analysis found L-citrulline reduced muscle soreness at 24 and 48 hours after exercise. The effect is consistent but modest.

Is L-citrulline safe with blood pressure medication or sildenafil?

L-citrulline lowers blood pressure modestly, which adds to antihypertensives, nitrates and PDE5 inhibitors like sildenafil. Do not combine it with nitrates or sildenafil without medical advice.

Scientific references

Where to buy

Nutricost, L-Citrulline Malate 2:1, Unflavored, 21.4 oz (600 g)

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