Supplement
L-Arginine
The nitric oxide precursor that its own precursor beats, with small real effects and one serious landmark warning.
L-arginine is the amino acid from which the body makes nitric oxide, the vessel-relaxing signal. We grade L-Arginine C+ on evidence and C+ for worth-it at about $10-20 per month.
Evidence
Worth it
Typical cost: $10-20/month
What it does
L-arginine is the amino acid from which the body makes nitric oxide, the vessel-relaxing signal. It is sold for blood flow: athletic pumps, blood pressure, and erectile function. It is also the middle of a pathway this library grades at three points: citrulline before it, and the nitrate pathway (beetroot) beside it.
What the research says
Lowers blood pressure modestly in pooled small trials
Evidence: emerging. Dong 2011 meta-analysis (11 trials, 387 participants): oral arginine reduced systolic pressure by about 5.4 and diastolic by about 2.7 mmHg versus control, mostly in short trials with mixed populations. A real pooled effect of the size this library grades as modest wherever it appears.
Improves erection quality in men with erectile dysfunction, in meta-analysis
Evidence: emerging. Rhim 2019 pooled 10 trials (540 men, 1.5 to 5 g/day): arginine, alone or with partners like pine bark extract, improved sexual function scores and erection hardness versus placebo, with the cleanest signal in mild-to-moderate cases. Small trials, short durations, some combination products muddying attribution.
The exercise 'pump' does not convert to performance in trained people
Evidence: moderate. Arginine raises nitric oxide markers; meta-analyses of performance outcomes in healthy athletes find no consistent benefit for strength, endurance, or body composition. The physiology is visible in blood work and absent on the stopwatch, the mirror image of its precursor problem: oral arginine is heavily broken down in the gut and liver, which is why citrulline raises arginine levels more efficiently (see the L-citrulline record, graded C+).
Arginine is a precursor in search of a delivery system. Its downstream product (nitric oxide) matters, its oral bioavailability is poor, its best pooled effects are modest (blood pressure, erectile function), its athletic reputation fails its own meta-analyses, and it carries one of the supplement literature's clearest context-specific harms (post-heart-attack, in the safety notes). C+ for real-but-small benefits in two niches, delivered by a compound its own precursor out-performs.
The week's longevity and biohacking news.
This grade for L-Arginine rests on the record above. When a new result changes that record, the grade changes with it, and the Thursday email is where the change lands first: the week's longevity and biohacking news, in plain English, linked back to the reasoning on this page.
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Every grade follows a published rubric, and sponsors never change one. When the evidence moves a grade, Thursday is where you hear it first, before you renew a stack that stopped earning its cost.
Is it worth it?
Evidence (C+) sits below the leaderboard floor, so the worth-it grade is capped at C+ however inexpensive it is; the derived value lands at the cap. About $15 a month at common doses. Derived from the October 2026 worth-it model.
Typical cost
$10-20/month
Common form, not a brand recommendation
Dosage context established
Blood pressure trials used roughly 4 to 24 g/day in divided doses (a wide, unsatisfying range); erectile trials 1.5 to 5 g/day. GI tolerance caps practical intake: single doses above about 9 to 10 g commonly cause diarrhea. Citrulline at 3 to 6 g raises plasma arginine more than equivalent arginine doses, the pharmacokinetic fact that organizes this whole category.
Worth-it leaderboard
L-Arginine sits outside the worth-it top 20.
L-Arginine sits outside the current top 20 on the gated leaderboard. The leaders below clear an evidence floor of B- before price counts at all, so cheap alone never earns a rank.
See the full worth-it leaderboard →
When the evidence moves a grade, this ranking moves with it. Thursday is where you hear it first.
Safety notes
The landmark caution: VINTAGE MI (JAMA 2006) randomized older patients after a heart attack to arginine 3 g three times daily or placebo and was stopped early after 6 deaths in the arginine group versus none on placebo, with no benefit; arginine should not be used after a recent heart attack. Otherwise the tolerance issues are gastrointestinal (nausea, cramping, diarrhea at higher single doses). Caution applies with blood-pressure medication and nitrates (additive lowering), and herpes folklore aside, arginine-rich supplementation is sometimes avoided by people managing frequent herpes outbreaks on a long-standing, weakly evidenced rationale this record notes without endorsing.
Longevity Lab Report
L-Arginine news. Graded when it happens.
The grade on this page stays free. The email carries the news on l-arginine: expert moves, dose changes, and what is working, in plain English every Thursday.
Changelog
Last updated 2026-10-23
- 2026-10-23|Graded from the blood pressure and erectile-function meta-analyses, the performance-outcome meta-analyses, and the VINTAGE MI safety trial in the safety notes. Cross-referenced with the graded L-citrulline record, which covers the precursor comparison this ingredient's marketing usually omits.
- 2026-10-23|Listed under heart, matching this record's graded blood pressure findings. Fitness is not listed: the performance meta-analyses are null, and tags follow graded findings.