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L-Arginine
Primary substrate for nitric oxide production — dilates blood vessels to improve circulation, exercise performance, and cardiovascular health.
What the evidence says
Arginine helped in about half (11/19) of the studies that measured an effect — promising, but not unanimous.
Most evidence is from high-quality meta-analyses and randomised trials published 2007–2026 with a typical study size of 578 participants.
Based on 36 studies · 27 meta-analyses · 6 RCTs · 27,887 total participants
Confidence
HighWhat the studies found
By outcome
Arginine has an evidence score of 9/10 — very strong evidence based on 52 indexed studies, including 31 meta-analyses. Primary substrate for nitric oxide production — dilates blood vessels to improve circulation, exercise performance, and cardiovascular health.
The commonly studied dose of Arginine is 3-6g daily. Research points to an estimated optimal dose around 6g, with a minimum effective dose near 3g. Individual response varies — start low and adjust.
The best time to take Arginine is between meals. It can be taken on an empty stomach. L-arginine competes with lysine and other cationic amino acids for absorption via the y+ and b0,+ transport systems.
Last reviewed May 2026 · evidence from 40 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
L-Arginine is a semi-essential amino acid that serves as the primary substrate for nitric oxide (NO) production. Nitric oxide is a powerful vasodilator that relaxes blood vessels, improving blood flow throughout the body. This makes arginine popular for cardiovascular health, exercise performance, and erectile function. While the body can produce arginine, supplementation may benefit those with increased demands or impaired synthesis.
Substrate for NO synthase enzymes
Relaxes blood vessel walls for improved flow
May stimulate GH release
How Arginine works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
3-6g daily
Loading: Not required; can split into 2-3 doses throughout the day
Take with food
| Form | Type |
|---|---|
| 💊L-Arginine powder or capsules | Recommended |
| 💊L-Arginine HCl | Alternative |
| 💊AAKG (Arginine Alpha-Ketoglutarate) | Alternative |
Pure L-Arginine has relatively low oral bioavailability. Citrulline may be a superior choice for nitric oxide support.
Minimum: 2 weeks
Optimal: 8 weeks
Cycling: Not required
Note: Taking on an empty stomach may increase GI discomfort. Citrulline may be more effective as it converts to arginine with better bioavailability.
Based on meta-analysis showing mean reductions of 5.39 mmHg systolic and 2.66 mmHg diastolic. Effects are modest and may not be clinically significant for all individuals. GI side effects increase notably above 6g.
Better circulation and oxygen delivery
Greater blood flow to working muscles during exercise
May modestly reduce blood pressure
May cause digestive upset at higher doses
Consult healthcare provider
May trigger outbreaks; balance with lysine
May enhance hypotensive effects
May cause excessive blood pressure drop
Combined vasodilation effects
Tip: Take with food; reduce dose; try citrulline instead
Tip: Divide into smaller doses
Arginine is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are GI discomfort, bloating. Use caution if any of these apply to you: History of herpes (may reactivate outbreaks); Recent heart attack; Low blood pressure.
Citrulline Malate
Likely helpsCombines citrulline for nitric oxide production with malic acid for ATP synthesis — reduces fatigue and enhances exercise endurance.
Tap node to isolate • Pinch to zoom • Tap edge for research