L-arginine is an amino acid that the body uses to make nitric oxide, a signal that relaxes blood vessels, and it is the classic ingredient in “nitric oxide” pre-workout supplements. Taken by mouth, much of it is broken down in the gut and liver before it reaches the blood, which is why many researchers now prefer L-citrulline for raising blood arginine. An intravenous arginine product is FDA-approved, but only as a diagnostic test of growth hormone release.
The most important facts are these. Oral doses of 5–9 g raise growth hormone slightly at rest, but taking arginine before resistance training blunted the exercise growth hormone response in two trials. Meta-analyses suggest small blood pressure reductions. For exercise performance the evidence is mixed and of low quality. In the VINTAGE MI trial, patients given arginine after a heart attack had more deaths than those on placebo, and the trial closed enrollment early.
This page summarizes what clinical trials, meta-analyses and the FDA label report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Class | Amino acid; substrate for nitric oxide synthase |
| Formula | C₆H₁₄N₄O₂, 174.20 g/mol |
| Common forms | L-arginine (free base), L-arginine hydrochloride, arginine alpha-ketoglutarate (AAKG) |
| Route | Oral (supplements); intravenous (R-Gene 10, a diagnostic product) |
| Oral bioavailability | About 20% for a single 10 g dose in healthy volunteers |
| Doses studied | 5–13 g single oral doses (growth hormone studies); 4–24 g/day (blood pressure trials); 3 g three times a day (VINTAGE MI); 12 g/day AAKG (exercise trials) |
| FDA-approved product | R-Gene 10 (arginine hydrochloride injection), labeled only as a test of pituitary growth hormone reserve |
| US supplement status | Sold as a dietary supplement; the NIH label database returned more than 1,300 labels mentioning arginine alpha-ketoglutarate alone (November 2026) |
| WADA status | Not named on the 2026 Prohibited List |
What it is
L-arginine is one of the amino acids that make up proteins (PubChem). Its supplement appeal comes from a second role: it is the substrate that nitric oxide synthase uses to make nitric oxide (Dong et al., Am Heart J 2011). Nitric oxide widens blood vessels, so the idea behind “NO boosters” is that more arginine means more nitric oxide, more blood flow to muscle and a better “pump.”
That chain of reasoning breaks down at several points, which the rest of this page covers:
- Absorption. Oral arginine is extensively cleared before it reaches the circulation, largely because the enzyme arginase in the intestine breaks it down (Schwedhelm et al., Br J Clin Pharmacol 2008).
- Nitric oxide output. A higher blood arginine level does not by itself raise blood flow during exercise. In a 7-day trial of an AAKG product, blood arginine rose but the increases in blood flow and nitric oxide markers were the same as with placebo (Willoughby et al., IJSNEM 2011).
- Growth hormone. Arginine does stimulate growth hormone, but the oral effect is small and combining it with exercise appears to reduce, not add to, the response (see below).
Arginine vs citrulline and AAKG
| Form | What it is | Key finding |
|---|---|---|
| L-arginine | The amino acid itself | About 20% of a 10 g oral dose reached the blood (Tangphao et al. 1999) |
| L-citrulline | An amino acid the body converts to arginine | Raised plasma arginine (peak and total exposure) more effectively than the same daily amount of arginine in a 20-person crossover trial (Schwedhelm et al. 2008) |
| Arginine alpha-ketoglutarate (AAKG) | Arginine paired with alpha-ketoglutarate, a citric acid cycle intermediate | Raises plasma arginine; performance results conflict (Campbell et al. 2006; Wax et al. 2012) |
Other nitric oxide–related supplements in this library include beetroot (dietary nitrate), which raises nitric oxide through a different pathway that does not need nitric oxide synthase, and agmatine sulfate, a breakdown product of arginine.
Pharmacokinetics
The key human study gave 10 healthy volunteers a single 30 g intravenous dose (over 30 minutes) and, on another occasion, a single 10 g oral dose (Tangphao et al., Br J Clin Pharmacol 1999):
| Measure | Result |
|---|---|
| Baseline plasma arginine (diet only, 12 controls) | 15.1 ± 2.6 µg/mL |
| Peak after 30 g IV | 1,390 ± 596 µg/mL |
| Peak after 10 g oral | 50.0 ± 13.4 µg/mL, reached about 1 h after the dose |
| Absolute oral bioavailability | About 20% |
| Elimination | Biphasic: a rapid early fall due to kidney clearance at high concentrations, then slower non-kidney elimination. No kidney elimination was seen after the 10 g oral dose |
In other words, even a large 10 g oral dose raised peak blood arginine only about threefold over the dietary baseline, while the intravenous dose raised it roughly ninetyfold.
The citrulline comparison came from a double-blind, randomized, placebo-controlled crossover trial in 20 healthy volunteers who took six different dosing regimens for a week each (Schwedhelm et al., Br J Clin Pharmacol 2008):
- Citrulline raised plasma arginine more effectively than arginine itself, and dose dependently.
- The highest citrulline dose (3 g twice daily) raised the ratio of arginine to ADMA (an internal inhibitor of nitric oxide synthase) from 186 to 278 and increased urinary nitrate and cGMP, markers of nitric oxide signaling.
- No regimen, citrulline or arginine, improved flow-mediated dilation (a standard measure of blood vessel function) over baseline. Only a pooled analysis found a correlation between a rising arginine/ADMA ratio and better dilation.
Approved medical use
The only FDA-approved arginine product on DailyMed is R-Gene 10, a 10% arginine hydrochloride injection (DailyMed, R-Gene 10 label 2024). According to the label:
- It is indicated as “an intravenous stimulant to the pituitary for the release of human growth hormone,” that is, a diagnostic test of growth hormone reserve, not a treatment.
- The adult dose is 30 g arginine hydrochloride (300 mL) by intravenous infusion; the pediatric dose is 0.5 g/kg.
- Overdose in children can cause hyperchloremic metabolic acidosis (excess acid in the blood), and hypersensitivity reactions including anaphylaxis have been reported.
- Reported side effects include nausea, vomiting, headache, flushing, numbness and local vein irritation, and leakage outside the vein has caused burn-like skin damage.
Oral arginine sold as a supplement has no FDA-approved use.
What the research shows
Growth hormone release
Because intravenous arginine is used to provoke growth hormone release in testing, oral arginine has been marketed as a “natural GH booster.” The trials show a small effect that does not combine well with exercise.
| Study | Design | Main result |
|---|---|---|
| Collier et al., Growth Horm IGF Res 2005 | 8 healthy young men; single oral doses of 5, 9 or 13 g vs placebo; blood sampled every 10 min for 5 h | 5 g and 9 g raised growth hormone (area under the curve 301.5 and 524.3 vs 186.0 min·µg/L for placebo). Mean peaks were 3.9 and 6.4 µg/L vs 2.9 µg/L. The rise started about 30 min after the dose and peaked at about 60 min. 13 g caused considerable gastrointestinal distress in most subjects and no larger response |
| Collier et al., J Appl Physiol 2006 | 8 healthy men; 7 g arginine or placebo, with or without resistance exercise | Exercise alone produced the largest growth hormone response (508.7 min·ng/mL). Arginine plus exercise gave a smaller response (260.5) than exercise alone |
| Forbes et al., IJSNEM 2014 | 14 strength-trained men; 0.075 g/kg arginine or placebo before resistance exercise, double-blind crossover | Plasma arginine rose about 120%, but the growth hormone response was blunted (288.4 vs 487.9 min·ng/mL with placebo); IGF-1 did not change |
The authors of the 2006 study suggested that the pituitary may enter a refractory period, so that two stimuli close together suppress rather than add to each other (Collier et al. 2006). For context, the short growth hormone pulses seen after oral arginine are far smaller and briefer than the exposure produced by injected growth hormone or by growth hormone secretagogues such as ibutamoren (MK-677).
Exercise performance
The evidence is inconsistent and generally of low quality.
| Review | Scope | Conclusion |
|---|---|---|
| Viribay et al., Nutrients 2020 | 18 studies in the review, 15 in the meta-analysis | Reported improvements in aerobic (SMD 0.84, 95% CI 0.12–1.56, I² = 89%) and anaerobic tests (SMD 0.24, 95% CI 0.05–0.43). Suggested 0.15 g/kg taken 60–90 min before exercise |
| Trexler, Nutrients 2025 | Published comment on Viribay et al. | Argued that the meta-analysis contained multiple errors common in sports nutrition meta-analyses that distort pooled effect estimates |
| Brooks et al., Nutr Rev 2016 | 62 articles on arginine alone or with caffeine and/or creatine, in healthy adults aged 19–50 | Most studies were small with risk of bias; arginine “provided little enhancement of athletic performance or improvements in recovery,” and the evidence did not support its use |
SMD (standardized mean difference) is an effect size; 0.2 is conventionally “small” and 0.8 “large.” The very high heterogeneity in the aerobic result (I² = 89%) means the included studies disagreed strongly, and the published critique questions how the pooled numbers were calculated. The independent 2016 review, prepared for military health authorities, reached a negative conclusion.
Arginine alpha-ketoglutarate (AAKG)
AAKG is the form used in many “NO” products.
| Trial | Participants | Dose, duration | Result |
|---|---|---|---|
| Campbell et al., Nutrition 2006 | 35 resistance-trained men aged 30–50 | 4 g three times a day (12 g/day) for 8 weeks with training, vs placebo | Greater gains in 1-repetition-maximum bench press and Wingate peak power; no difference in body composition, muscle endurance or aerobic capacity |
| Willoughby et al., IJSNEM 2011 | 24 active men | 12 g/day of an AAKG product (NO₂ Platinum) for 7 days | Plasma arginine rose; blood flow, heart rate, blood pressure and nitric oxide markers changed the same way as with placebo |
| Wax et al., JISSN 2012 | 8 trained and 8 untrained men | Single 3 g dose 45 min before exercise, double-blind crossover | No effect on 1-repetition maximum or total load lifted in bench press or leg press |
Blood pressure
This is the most consistent finding for oral arginine, though the trials are small.
| Meta-analysis | Trials, participants | Effect vs placebo |
|---|---|---|
| Dong et al., Am Heart J 2011 | 11 double-blind RCTs, 387 participants; 4–24 g/day | Systolic −5.39 mm Hg (95% CI −8.54 to −2.25); diastolic −2.66 mm Hg (95% CI −3.77 to −1.54) |
| Shiraseb et al., Adv Nutr 2022 | 22 RCTs (30 effect sizes) | Systolic −6.40 mm Hg; diastolic −2.64 mm Hg. Effective dose for systolic pressure ≥4 g/day; no significant change at more than 9 g/day, with trials longer than 24 days, or in obese participants |
| Shi et al., Nitric Oxide 2026 | 5 RCTs, 202 participants, using 24-hour ambulatory monitoring | 24-hour systolic −4.23 mm Hg; diastolic −3.04 mm Hg. The authors noted the small number of studies |
These are modest reductions, smaller than those from standard blood pressure drugs such as lisinopril or amlodipine, and no trial has shown that arginine prevents heart attacks or strokes.
Erectile function
A 2019 meta-analysis of 10 RCTs (540 men with mild to moderate erectile dysfunction) found that arginine at 1,500–5,000 mg/day, alone or combined with other substances, improved erectile dysfunction compared with placebo or no treatment (odds ratio 3.37, 95% CI 1.29–8.77) (Rhim et al., J Sex Med 2019). Adverse effects occurred in 8.3% on arginine vs 2.3% on control, none severe. Dosage and duration varied widely between studies. Approved erectile dysfunction drugs include sildenafil and tadalafil.
After a heart attack: VINTAGE MI
VINTAGE MI was a single-center, randomized, double-blind, placebo-controlled trial in 153 patients after a first ST-elevation myocardial infarction (a major heart attack) (Schulman et al., JAMA 2006):
| Feature | VINTAGE MI |
|---|---|
| Dose | Goal of 3 g three times a day for 6 months, on top of standard post-infarction therapy |
| Primary outcome | Change in ejection fraction (heart pumping function) in patients aged 60 and older |
| Efficacy result | No change in vascular stiffness or ejection fraction in either group |
| Safety result | 6 deaths (8.6%) in the arginine group vs none on placebo (p = 0.01) |
| Outcome | The data and safety monitoring committee closed enrollment because of safety concerns |
The investigators concluded that arginine “should not be recommended following acute myocardial infarction.”
Side effects and risks
- Digestive upset. In the dose-finding study, 13 g caused considerable gastrointestinal distress in most participants (Collier et al. 2005). The 2016 systematic review concluded that short-term supplementation may cause gastrointestinal and cardiovascular adverse effects (Brooks et al. 2016).
- Heart attack survivors. The higher death rate in VINTAGE MI is the most serious safety signal (Schulman et al. 2006).
- “NO” product case reports. A poison-center group described three young men who went to the emergency department with palpitations, dizziness, near-fainting or fainting after using AAKG-based “nitric oxide” supplements; two were admitted. The authors noted that vasodilation could explain the symptoms but other causes could not be excluded (Prosser et al., Hum Exp Toxicol 2009).
- Blood pressure drugs. Because arginine lowers blood pressure slightly in trials, effects could add to those of antihypertensive drugs or PDE5 inhibitors. This is an inference from the trial data, not a documented interaction study.
- Intravenous use. The R-Gene 10 label warns about acidosis after pediatric overdose, anaphylaxis and skin damage from extravasation (DailyMed 2024).
Sports and anti-doping
Arginine is not named on the WADA 2026 Prohibited List. However, intravenous infusions or injections of more than 100 mL per 12 hours are prohibited at all times outside legitimate hospital treatment, surgery or clinical diagnostic tests, so an arginine drip would fall under that rule (M2.2) (WADA 2026 Prohibited List). Multi-ingredient “pump” products should be judged on all of their ingredients.
Key takeaways
- A nitric oxide precursor with poor oral delivery. Only about 20% of a 10 g oral dose reached the blood, and citrulline raised blood arginine more effectively than arginine itself.
- Approved only as a diagnostic. The FDA-approved product is an intravenous growth hormone stimulation test, not a treatment.
- The GH effect is small and clashes with training. 5–9 g raised resting growth hormone modestly, 13 g mainly caused stomach upset, and arginine before resistance exercise blunted the exercise growth hormone response in two trials.
- Performance evidence is weak. One meta-analysis reported benefits but has been criticized for methodological errors; an independent review found little benefit, and AAKG trials conflict.
- Modest blood pressure reduction. Meta-analyses show roughly 4–6 mm Hg lower systolic pressure in small trials.
- Not for heart attack survivors. VINTAGE MI found no benefit and more deaths on arginine.
Sources
- National Center for Biotechnology Information. L-arginine (CID 6322). PubChem. PubChem.
- Tangphao O, Grossmann M, Chalon S, Hoffman BB, Blaschke TF. Pharmacokinetics of intravenous and oral L-arginine in normal volunteers. Br J Clin Pharmacol. 1999;47(3):261–266. PubMed.
- Schwedhelm E, Maas R, Freese R, et al. Pharmacokinetic and pharmacodynamic properties of oral L-citrulline and L-arginine: impact on nitric oxide metabolism. Br J Clin Pharmacol. 2008;65(1):51–59. PubMed.
- US National Library of Medicine. R-Gene 10 (arginine hydrochloride) injection, solution. Prescribing information, Pharmacia & Upjohn. 2024. DailyMed.
- Collier SR, Casey DP, Kanaley JA. Growth hormone responses to varying doses of oral arginine. Growth Horm IGF Res. 2005;15(2):136–139. PubMed.
- Collier SR, Collins E, Kanaley JA. Oral arginine attenuates the growth hormone response to resistance exercise. J Appl Physiol. 2006;101(3):848–852. PubMed.
- Forbes SC, Harber V, Bell GJ. Oral L-arginine before resistance exercise blunts growth hormone in strength trained males. Int J Sport Nutr Exerc Metab. 2014;24(2):236–244. PubMed.
- Viribay A, Burgos J, Fernández-Landa J, Seco-Calvo J, Mielgo-Ayuso J. Effects of arginine supplementation on athletic performance based on energy metabolism: a systematic review and meta-analysis. Nutrients. 2020;12(5):1300. PubMed.
- Trexler ET. Common errors in sports nutrition meta-analyses lead to distortion of pooled effect estimates. Comment on Viribay et al. Nutrients. 2025;17(14):2375. PubMed.
- Brooks JR, Oketch-Rabah H, Low Dog T, et al. Safety and performance benefits of arginine supplements for military personnel: a systematic review. Nutr Rev. 2016;74(11):708–721. PubMed.
- Campbell B, Roberts M, Kerksick C, et al. Pharmacokinetics, safety, and effects on exercise performance of L-arginine alpha-ketoglutarate in trained adult men. Nutrition. 2006;22(9):872–881. PubMed.
- Willoughby DS, Boucher T, Reid J, Skelton G, Clark M. Effects of 7 days of arginine-alpha-ketoglutarate supplementation on blood flow, plasma L-arginine, nitric oxide metabolites, and asymmetric dimethyl arginine after resistance exercise. Int J Sport Nutr Exerc Metab. 2011;21(4):291–299. PubMed.
- Wax B, Kavazis AN, Webb HE, Brown SP. Acute L-arginine alpha ketoglutarate supplementation fails to improve muscular performance in resistance trained and untrained men. J Int Soc Sports Nutr. 2012;9(1):17. PubMed.
- Dong JY, Qin LQ, Zhang Z, et al. Effect of oral L-arginine supplementation on blood pressure: a meta-analysis of randomized, double-blind, placebo-controlled trials. Am Heart J. 2011;162(6):959–965. PubMed.
- Shiraseb F, Asbaghi O, Bagheri R, Wong A, Figueroa A, Mirzaei K. 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;13(4):1226–1242. PubMed.
- Shi Y, Liu Y, Zhou Z, Xu S, Luo P. Reassessment of the effect of oral L-arginine on blood pressure: a systematic review and meta-analysis based on ambulatory blood pressure monitoring. Nitric Oxide. 2026;164:60–68. PubMed.
- Rhim HC, Kim MS, Park YJ, et al. The potential role of arginine supplements on erectile dysfunction: a systemic review and meta-analysis. J Sex Med. 2019;16(2):223–234. PubMed.
- Schulman SP, Becker LC, Kass DA, et al. L-arginine therapy in acute myocardial infarction: the Vascular Interaction With Age in Myocardial Infarction (VINTAGE MI) randomized clinical trial. JAMA. 2006;295(1):58–64. PubMed.
- Prosser JM, Majlesi N, Chan GM, Olsen D, Hoffman RS, Nelson LS. Adverse effects associated with arginine alpha-ketoglutarate containing supplements. Hum Exp Toxicol. 2009;28(5):259–262. PubMed.
- National Institutes of Health, Office of Dietary Supplements. Dietary Supplement Label Database: search for “arginine alpha-ketoglutarate” (accessed November 2026). NIH DSLD.
- World Anti-Doping Agency. The 2026 Prohibited List. In force January 1, 2026. WADA.