L-arginine
Summary
L-arginine is an amino acid and the raw material for nitric oxide. Pooled trials report lower blood pressure, about 6 mm Hg systolic, and a meta-analysis in mild to moderate erectile dysfunction found more improvement than placebo. After a heart attack, a trial was stopped early when six people on arginine died versus none on placebo.
Key facts
- A conditionally essential amino acid from dietary protein; the substrate for nitric oxide synthase[1]
- 22 RCTs: systolic about 6.4 mm Hg and diastolic about 2.6 mm Hg lower than placebo[1]
- 10 RCTs (540 men with mild to moderate ED): improvement more likely than with placebo at 1.5–5 g/day[2]
- The VINTAGE MI trial closed enrollment after 6 deaths on arginine versus none on placebo[3]
- 2 graded human outcomes on this page
- October 11, 2026
How it works
EstablishedArginine is converted to nitric oxide, which relaxes blood-vessel walls; this underlies proposed effects on blood pressure and erections.[1][2]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Sexual function | Grade C | Improved | Meta-analysis of 10 trials · n = 540 · 2019 | 1 row |
| Heart safety | Grade C | Worsened | RCT · n = 153 · 2006 | 1 row |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Erectile function in mild to moderate ED | Improved | Grade C | Meta-analysis · n = 540 · 2019 Men with mild to moderate erectile dysfunction in 10 RCTs Form: Arginine alone or with other ingredients · Dose: 1,500–5,000 mg/day · Duration: Varied across trials Improvement was more likely than with placebo or no treatment (odds ratio 3.37); side effects were more common (8.3% vs 2.3%) but none severe. Several trials combined arginine with other substances. | 30770070 (opens PubMed)Source [2] |
| Vascular stiffness, heart function and deaths after heart attack | Worsened | Grade C | RCT · n = 153 · 2006 Adults after a first ST-elevation heart attack, on standard therapy Form: L-arginine · Dose: Goal of 3 g three times daily (9 g/day) · Duration: 6 months Vascular stiffness and ejection fraction did not change; 6 people (8.6%) on arginine died versus none on placebo, and enrollment was closed for safety. | 16391217 (opens PubMed)Source [3] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| L-arginine (free form or HCl) | Varies | No head-to-head human absorption data in the sources cited here. | Side effects in 8.3% versus 2.3% on placebo in ED trials, none severe.[2] | Blood pressure, erectile function and post-heart-attack trials |
Studied doses
Doses studied in human trials ranged from 1,500 mg to 9,000 mg of L-arginine per day; blood-pressure benefits were not significant above 9 g/day or beyond 24 days in subgroup analyses.[2][3][1]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- People who have had a heart attack
- In the VINTAGE MI trial, arginine added to standard care did not help and was associated with more deaths.[3]
- Low blood pressure or blood-pressure medicines
- Arginine lowers blood pressure in pooled trials, so effects could add to low baseline pressure or medicines.[1]
- Erectile dysfunction without a check-up
- ED can signal heart disease; trials only included mild to moderate cases.[2]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
Frequently asked questions
Does L-arginine lower blood pressure?
Pooled trials report about 6.4 mm Hg lower systolic pressure, but benefits were not significant in trials longer than 24 days or above 9 g/day.[1]
Does L-arginine help erectile dysfunction?
In 10 trials of men with mild to moderate ED, improvement was more likely than with placebo, though some products combined arginine with other ingredients.[2]
Is L-arginine safe after a heart attack?
A trial in heart-attack survivors was stopped early after 6 deaths on arginine versus none on placebo.[3]
How does arginine compare with citrulline?
Citrulline is converted to arginine in the body; see the citrulline page for its own trial evidence.
Sources
- [1]Effect of l-Arginine Supplementation on Blood Pressure in Adults: A Systematic Review and Dose-Response Meta-analysis of Randomized Clinical Trials. Adv Nutr, 2022. meta-analysis
- [2]The Potential Role of Arginine Supplements on Erectile Dysfunction: A Systemic Review and Meta-Analysis. J Sex Med, 2019. meta-analysis
- [3]L-arginine therapy in acute myocardial infarction: the Vascular Interaction With Age in Myocardial Infarction (VINTAGE MI) randomized clinical trial. JAMA, 2006. RCT
What changed
- New monograph: definition, key facts, evidence table, studied doses, safety and FAQ written from the cited abstracts and fact sheets.