L-Arginine
L-Arginine
TL;DR
L-arginine is the direct substrate for nitric oxide synthase, but heavy first-pass metabolism by intestinal arginase means oral doses raise plasma arginine far less efficiently than citrulline does. It has real evidence in blood pressure and endothelial function at 6-12 g/day, and a clear contraindication after myocardial infarction.
Ideal For
- Adults with mild hypertension seeking an adjunct alongside standard measures
- People with documented endothelial dysfunction
- Patients in supervised wound-healing or surgical recovery protocols
- Those with erectile dysfunction of vascular origin, typically combined with pycnogenol
Avoid If
- You have had a recent myocardial infarction — the VINTAGE MI trial found increased mortality
- You have herpes simplex, since arginine can favour viral replication over lysine
- You have asthma, where inhaled and oral arginine have worsened airway inflammation in some studies
- You have significant renal or hepatic impairment
- You are taking nitrates or PDE5 inhibitors without medical advice — additive hypotension
Frequently Asked Questions
Overview
Arginine sits at the centre of the nitric oxide story, which is why it became the original "pump" supplement. The pharmacology is less flattering than the biochemistry. Orally administered arginine is extensively degraded by arginase in the gut wall and liver before it reaches circulation, so bioavailability is roughly 20% and highly variable. Meta-analyses still find a genuine effect: pooled trials show reductions of about 5 mmHg systolic and 3 mmHg diastolic blood pressure, and improvements in flow-mediated dilation in people with existing endothelial dysfunction. Healthy young athletes, whose nitric oxide production is not limiting, see little. The VINTAGE MI trial is the important safety datum — arginine added to standard care after myocardial infarction was associated with higher mortality, and the trial was stopped early. Between the poor bioavailability and that signal, L-citrulline has largely displaced arginine for performance and vascular use, since citrulline evades arginase and raises plasma arginine more effectively than arginine itself. Arginine retains a place in wound healing, where its role in collagen synthesis and immune function is better established.
How It Works
- Serves as the direct substrate for endothelial nitric oxide synthase
- Nitric oxide activates guanylate cyclase, relaxing vascular smooth muscle
- Feeds the urea cycle, supporting ammonia clearance during protein load
- Precursor to proline and ornithine, supporting collagen deposition in wound healing
- Stimulates growth hormone release at high intravenous but not typical oral doses
- Extensively degraded by intestinal and hepatic arginase before reaching circulation
Quick Facts
- Nitric oxide precursor
- Supports blood flow
- Wound healing support
- Immune function enhancement
- Growth hormone release
Benefits & Outcomes
Pump Enhancement
Oral arginine barely raises plasma arginine because most is destroyed before it reaches circulation.
Nitric Oxide Production
Poor oral bioavailability makes it the wrong choice - use citrulline.
Wound Healing
Arginine shows benefit in pressure ulcers as part of combined nutritional formulas.
Erectile Function
Citrulline raises arginine levels more effectively than arginine itself — prefer citrulline.
Growth Hormone Support
Produces a measurable GH spike with no meaningful downstream benefit.
Supporting Research17 studies
Oral treatment with L-lysine and L-arginine reduces anxiety and basal cortisol levels in healthy humans
Smriga M, Ando T, Akutsu M
Combined L-lysine and L-arginine (2.64 g/day) reduced trait anxiety and salivary cortisol responses to stress in healthy adults.
L-arginine therapy in acute myocardial infarction: the Vascular Interaction With Age in Myocardial Infarction (VINTAGE MI) randomized clinical trial
Schulman SP, Becker LC, Kass DA +9 more
L-arginine did not improve vascular stiffness or ejection fraction and was associated with higher mortality, leading to early trial termination.
Oral L-arginine supplementation and cutaneous vascular responses in patients with primary Raynaud's phenomenon
Khan F
In 20 patients with primary Raynaud's phenomenon, four weeks of oral L-arginine did not improve cutaneous blood flow responses to cold challenge or to endothelium-dependent vasodilators, and attack frequency and severity were unchanged versus placebo.
Treatment of erectile dysfunction with pycnogenol and L-arginine
Stanislavov R, Nikolova V
We conclude that oral administration of L-arginine in combination with Pycnogenol causes a significant improvement in sexual function in men with ED without any side effects.
The Potential Role of Arginine Supplements on Erectile Dysfunction: A Systematic Review and Meta-Analysis
Rhim HC, Kim MS, Park YJ +3 more
arginine supplements with dosage ranging from 1,500 to 5,000 mg significantly improved ED compared with placebo or no treatment (odds ratios, 3.37 [1.29, 8.77], P = .01, I2 = 44)
L-arginine supplementation in peripheral arterial disease: no benefit and possible harm
Wilson AM, et al.
As opposed to its short-term administration, long-term administration of L-arginine is not useful in patients with intermittent claudication and PAD.
Effect of oral L-arginine supplementation on blood pressure: a meta-analysis of randomized, double-blind, placebo-controlled trials
Dong JY, Qin LQ, Zhang Z +4 more
Oral L-arginine reduced systolic blood pressure by about 5.4 mmHg and diastolic by about 2.7 mmHg versus placebo.
Growth Hormone Response to L-Arginine Alone and Combined with Different Doses of Growth Hormone-Releasing Hormone: A Systematic Review and Meta-Analysis
Goli P, Yazdi M, Heidari-Beni M +1 more
Arginine (ARG) can modulate growth hormone (GH) release by suppressing its endogenous inhibitory regulator, somatostatin.
Oral L-arginine supplementation and endothelial function: a meta-analysis of randomized controlled trials
Bai Y, Sun L, Yang T +3 more
L-arginine improved flow-mediated dilation, but benefit was confined to impaired baseline endothelial function
Effect of administration of β-hydroxy-β-methyl butyrate-enriched formula after liver transplantation: A pilot randomized controlled trial
Kamo N, Kaido T, Uozumi R +1 more
Patients in the HMB group received two packs of HMB-rich nutrients per day, which contained calcium-HMB (1500 mg), l-arginine (7000 mg), and l -glutamine (7000 mg) per pack
Dietary Supplements for Erectile Dysfunction: Analysis of Marketed Products, Systematic Review, Meta-Analysis and Rational Use
Petre GC, Francini-Pesenti F, Vitagliano A +1 more
A metanalysis identified some nutraceuticals, such as Panax ginseng, Tribulus terrestris and L-arginine, that are able to improve male sexual function
Arginine and ornithine supplementation increases growth hormone and insulin-like growth factor-1 serum levels after heavy-resistance exercise in strength-trained athletes
Zajac A, Poprzecki S, Zebrowska A +2 more
Arginine and ornithine supplementation increases growth hormone and insulin-like growth factor-1 serum levels after heavy-resistance exercise in strength-trained athletes
The potential role of arginine supplements on erectile dysfunction: a systematic review and meta-analysis
Rhim HC, Kim MS, Park YJ +5 more
Arginine supplements at 1.5-5 g/day significantly improved erectile function scores versus placebo.
L-arginine supplementation fails to improve outcomes after acute myocardial infarction: the VINTAGE MI randomized trial
Schulman SP, Becker LC, Kass DA +3 more
L-arginine did not improve vascular stiffness and was associated with more deaths
Comparison of efficacy and safety of daily oral L-arginine and PDE5Is alone or in combination in treating erectile dysfunction: a systematic review and meta-analysis of randomised controlled trials
Gao L, Zhao Z, Zhang L +1 more
L-arginine alone improved IIEF scores versus placebo, and combination with PDE5 inhibitors outperformed PDE5 inhibitors alone.
Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis
Trexler ET, Persky AM, Ryan ED +3 more
Citrulline increased plasma arginine and nitric oxide availability
Citrulline malate supplementation and exercise performance: a systematic review and meta-analysis
Trexler ET, Persky AM, Ryan ED +3 more
Citrulline increased plasma arginine and nitric oxide availability
Safety Information
Potential Side Effects
Dose-dependent diarrhoea, bloating and nausea, particularly with the hydrochloride form. Hypotension at high doses, especially alongside antihypertensives. Herpes reactivation reported in susceptible people.
Contraindications
Recent myocardial infarction, active herpes outbreak, severe renal or hepatic impairment, asthma with poor control.
Drug Interactions
- Nitrates and PDE5 inhibitors such as sildenafil — additive hypotension
- Antihypertensive agents — additive blood pressure lowering
- Potassium-sparing diuretics — arginine infusions can raise serum potassium
- Anticoagulants — theoretical additive effect via nitric oxide-mediated platelet inhibition
Pregnancy & Breastfeeding
Pregnancy: insufficient_data
Breastfeeding: insufficient_data
Dosage Guidelines
Dosage Used in Studies
3000-6000 mg
Best Time to Take
Divided across two or three doses between meals
Best Form
L-arginine free base or sustained-release, though L-citrulline is the better choice for most vascular goals
Bioavailability
Roughly 20% oral bioavailability due to intestinal and hepatic arginase. Plasma response is saturable and inconsistent between individuals, which is the central reason citrulline outperforms it gram for gram.
Forms Compared
L-arginine HCl
L-arginine free base
Arginine alpha-ketoglutarate (AAKG)
Sustained-release arginine
L-citrulline
Food & Timing
On an empty stomach or between meals — dietary protein competes for the same cationic amino acid transporters
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.