Supplement analysis backed by scientific evidence · PT · ES · DE · FR

← All supplements
Moderate evidenceHeart & metabolic

L-Arginine

Arginine is the direct substrate for nitric oxide, but oral arginine is heavily degraded in the gut and liver before it reaches circulation, which is why citrulline usually outperforms it. It does modestly lower blood pressure; the pump-and-performance claims are much weaker.

View on iHerb Ships to 180+ countries · welcome discount for new customers

What the science says

  • Lowering blood pressure Moderate evidence

    A 2022 dose-response systematic review and meta-analysis of randomised trials found L-arginine supplementation significantly reduced both systolic and diastolic blood pressure, with reductions on the order of a few mmHg and larger effects in hypertensive participants. This is the best-supported arginine claim, though the magnitude is modest and typically requires 4-6 g/day or more.

  • Improving aerobic performance and VO2max Limited evidence

    A 2021 systematic review and meta-analysis found no significant overall effect of L-arginine supplementation on maximal oxygen uptake. Acute ergogenic trials are inconsistent, and the first-pass metabolism problem means oral arginine raises plasma arginine far less efficiently than citrulline does.

  • Erectile function Moderate evidence

    Small randomised trials of arginine, usually at 3-6 g/day and often combined with pycnogenol or other agents, report improvements in erectile function scores in men with mild-to-moderate ED. Trials are small, frequently use combination products, and effects are well below those of PDE5 inhibitors.

  • "Muscle pump" and hypertrophy Limited evidence

    Despite being the original pre-workout "NO booster," arginine has little controlled evidence for increased blood flow at practical oral doses, and no good evidence for added hypertrophy. Growth-hormone spikes reported after intravenous arginine do not occur meaningfully with oral dosing and would not drive muscle growth anyway.

Dosage & safety

Studied doseBlood pressure trials typically use 4-24 g/day in divided doses, with most benefit at 4-6 g/day or above. Erectile function studies use 1.5-6 g/day. Single doses above ~9 g commonly cause GI symptoms; L-citrulline at 3-6 g/day raises plasma arginine more effectively than arginine itself.
SafetyDiarrhoea, nausea and bloating are common above 9-10 g/day. Arginine can lower blood pressure additively with antihypertensives, nitrates and PDE5 inhibitors — combine only with medical advice. Do NOT use after a recent myocardial infarction: the VINTAGE MI trial found higher mortality in post-infarction patients given arginine. May reactivate herpes simplex in susceptible people. Caution in asthma (inhaled/oral arginine can worsen airway inflammation), and in kidney or liver impairment. Not a banned substance.

How to take it

TimingDivided across the day rather than as one large dose.
With food?On an empty stomach for absorption, but move it to a meal if you get diarrhoea.
Worth knowingSingle doses above about 9 g reliably cause GI symptoms; 3-6 g of citrulline gets your plasma arginine higher with none of that.

Interactions

With medications

  • nitrates for angina (isosorbide, nitroglycerin)

    Both increase nitric oxide signalling, and the combined vasodilation can drop blood pressure sharply. do not combine

  • PDE5 inhibitors such as sildenafil and tadalafil

    Additive vasodilation with a risk of symptomatic hypotension. do not combine without medical advice

  • antihypertensives

    Arginine lowers blood pressure on its own, so the effects add. monitor your blood pressure when starting and tell your prescriber

With other supplements

  • L-citrulline

    Citrulline converts to arginine, so stacking them is a redundant and larger nitric oxide load. pick one — citrulline raises plasma arginine more efficiently

  • L-lysine

    Lysine competes with arginine for the same intestinal and renal transporters, reducing the arginine you absorb. separate by at least 2 hours

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

Frequently asked questions

Does L-arginine lower blood pressure?

Yes, modestly — the evidence is moderate. A 2022 meta-analysis found L-arginine lowered systolic and diastolic blood pressure by a few mmHg, with most benefit at 4–6 g/day or more.

Does arginine improve workout performance or muscle pump?

No — the evidence is limited. A 2021 meta-analysis found no effect of L-arginine on VO2max, and there is little controlled evidence for a pump or added muscle growth at practical oral doses.

Is L-arginine or L-citrulline better?

L-citrulline at 3–6 g/day raises plasma arginine more effectively than L-arginine itself, because oral arginine is heavily broken down in the gut and liver. Single arginine doses above about 9 g also commonly cause GI symptoms.

Is L-arginine safe with sildenafil or nitrates?

No. Do not combine L-arginine with nitrates for angina, and do not take it with PDE5 inhibitors such as sildenafil without medical advice, because the vasodilation adds up. Do not use arginine after a recent heart attack either.

Scientific references

Where to buy

Vitacost, L-Arginine & L-Ornithine, 100 Capsules

View on iHerb

Ships to 180+ countries · welcome discount for new customers

Referral link — this site may earn a commission on purchases.

Related in Heart & metabolic