L-Arginine
Also known as: arginine, l-arginine (free form)
A 2019 meta-analysis of 10 randomized trials (n=540) found oral L-arginine (1.5–5 g/day) improved erectile dysfunction versus placebo. A 2022 meta-analysis of trials in hypertensive disorder and intrauterine growth restriction pregnancies reported benefits to birth weight, reduced risk of preeclampsia and small-for-gestational-age neonates, and increased plasma NO in IUGR; subgroup analyses noted dose and route differences and that intravenous but not oral administration drove some IUGR findings. A 2020 randomized crossover trial in severe asthma showed no reduction in exacerbations with oral L-arginine. Adverse effects in the ED trials were reported at 8.3% versus 2.3% with placebo and were not severe.
Last reviewed: 2026-10-14 · 4 indexed studies
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Overview
L-Arginine is a semi-essential amino acid and the substrate for nitric oxide synthesis. Clinical trials and meta-analyses have tested oral L-arginine for conditions including erectile dysfunction and pregnancy complications; results vary by indication and dose.
Mechanism & Function
Mechanism of Action
Provides substrate for nitric oxide synthesis, which can modulate vascular tone and placental blood flow; clinical abstracts link changes in NO-related metabolites with outcomes.
Physiological Role
Precursor for nitric oxide (endothelial signalling) and involved in pathways of vascular function and placental perfusion.
Primary Pathways
Performance / Health Relevance
May improve parameters that depend on vascular function, such as erectile function and fetal growth in certain pregnancy complications, via enhancement of nitric oxide availability.
Evidence Review
Practical Use & Dosage
- Minimum Effective Dose
- Approximately 1.5 g/day (evidence for erectile dysfunction starting at 1.5 g/day)
- Optimal Range
- 1.5–5 g/day for erectile dysfunction; pregnancy studies used various doses with subgroup signals at <4 g/day or higher doses depending on outcome and route
- Upper / Caution Level
- Not established (clinical trials reported up to 5 g/day; some pregnancy analyses suggest limiting intravenous use to <4 g/day)
- Timing
- Not specified in provided abstracts
- Best Format
- Oral powder or capsule
- Bioavailability
- Oral dosing was used in the cited trials; some pregnancy meta-analysis noted intravenous administration produced different results than oral.
- Absorption Considerations
- Not detailed in provided abstracts
Safety & Interactions
Side Effects
- •Mild adverse effects reported in trials (rate ~8.3% vs 2.3% placebo in ED meta-analysis)
Contraindications
- Not specified in provided abstracts
Drug Interactions
- •Not specified in provided abstracts
Who Should Avoid
- •Pregnant women should use only under clinical guidance (trial data in pregnancy contexts); specific contraindications not provided in abstracts
Monitoring
Monitor for adverse effects; in pregnancy and clinical contexts, outcomes such as blood pressure and fetal growth were measured in trials.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is L-Arginine typically used or indicated?
L-Arginine is most commonly used for: Erectile dysfunction, Support for pregnancy complications (IUGR, hypertensive disorders), General nitric oxide support, Adjunct in clinical supplementation regimens. Precursor for nitric oxide (endothelial signalling) and involved in pathways of vascular function and placental perfusion.
How does L-Arginine work?
Provides substrate for nitric oxide synthesis, which can modulate vascular tone and placental blood flow; clinical abstracts link changes in NO-related metabolites with outcomes.
What is the recommended dose of L-Arginine?
The optimal range is 1.5–5 g/day for erectile dysfunction; pregnancy studies used various doses with subgroup signals at <4 g/day or higher doses depending on outcome and route. with a minimum effective dose of Approximately 1.5 g/day (evidence for erectile dysfunction starting at 1.5 g/day). Best taken: Not specified in provided abstracts. Upper / caution level: Not established (clinical trials reported up to 5 g/day; some pregnancy analyses suggest limiting intravenous use to <4 g/day).
What are the side effects of L-Arginine?
Reported side effects include: Mild adverse effects reported in trials (rate ~8.3% vs 2.3% placebo in ED meta-analysis). Monitoring: Monitor for adverse effects; in pregnancy and clinical contexts, outcomes such as blood pressure and fetal growth were measured in trials.
Does L-Arginine interact with medications?
Known or theoretical interactions: Not specified in provided abstracts. Always check with a clinician before combining with prescription medication.
Who should avoid L-Arginine?
L-Arginine is generally not recommended for: Pregnant women should use only under clinical guidance (trial data in pregnancy contexts); specific contraindications not provided in abstracts; and Not specified in provided abstracts.
How strong is the evidence for L-Arginine?
Evidence level: Moderate (overall score 58/100), based on 4 indexed studies on SuppIndex.
Research & References (4)
The Potential Role of Arginine Supplements on Erectile Dysfunction: A Systemic Review and Meta-Analysis.
Systematic review and meta-analysis of 10 randomized controlled trials (540 patients) evaluating arginine supplements for erectile dysfunction.
l-Arginine supplementation in severe asthma.
Single-centre, crossover, double-blind RCT of oral L-arginine in severe asthma assessing exacerbations and plasma metabolites.
l-arginine supplementation improved neonatal outcomes in pregnancies with hypertensive disorder or intrauterine growth restriction: A systematic review and meta-analysis of randomized controlled trials.
Systematic review and meta-analysis of randomized trials of L-arginine in hypertensive disorder and IUGR pregnancies assessing neonatal outcomes and maternal preeclampsia risk.
Impact of preoperative beta-hydroxy-beta-methylbutyrate, arginine, and glutamine supplementation on inflammation in patients with cardiac surgery: A secondary analysis of a randomized controlled trial.
Secondary analysis of an open-label RCT giving preoperative supplementation with HMB plus 7 g L-glutamine and 7 g L-arginine twice daily versus routine care in older cardiac surgery patients, assessing inflammatory markers.
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Research Overview
Moderate EvidenceCite this ingredient
One-click citation export in APA, MLA, Chicago, BibTeX, or HTML. The URL below is stable and safe to link.
Stable URL
https://thesuppindex.com/ingredients/l-arginine
SuppIndex. (2026). L-Arginine: Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/l-arginine
Based on 4 indexed studies · Evidence level: Moderate.
Goal Ratings
Stack Compatibility
Used in combination with other amino acids (glutamine, HMB) in some perioperative or clinical trials; effects of combinations cannot be attributed to arginine alone.