Amino Acid
L-Arginine
Also known as: Arginine, L-Arginine HCl, L-Arginine Hydrochloride, Arginine HCl
A conditionally essential amino acid that serves as a precursor to nitric oxide, supporting vasodilation and blood flow. Most evidence supports benefits for endothelial function and exercise performance, though clinical results are mixed.
Last reviewed June 2026 · Evidence graded from peer-reviewed research, not editorial opinion. Educational only — not medical advice.
Every L-Arginine product we have scored
| # | Product | Score | Per serving |
|---|---|---|---|
| 1 | Nootropics Depot AAKG 2 | 90 A | $0.33 |
| 2 | Nutricost Pre-Workout For Women Powder | 89 A | $0.73 |
| 3 | Nutricost Pre-Workout Complex | 89 A | $0.83 |
| 4 | Pure Encapsulations L-Arginine | 88 A | $0.55 |
| 5 | NOW Foods L-Arginine Powder | 88 A | $0.34 |
| 6 | Thorne L-Arginine Plus | 87 A | $1.25 |
| 7 | Nootropics Depot AAKG 2:1 Powder | 86 A- | $0.33 |
| 8 | Pure Encapsulations Nitric Oxide Support | 82 A- | $1.70 |
| 9 | Bluebonnet Nutrition L-ARGININE 1000 mg | 82 A- | $0.96 |
| 10 | Country Life L-Arginine 500 mg | 82 A- | $0.17 |
| 11 | Thorne L-Arginine - Sustained Release | 81 A- | $0.73 |
| 12 | NOW Foods Tri-Amino | 81 A- | $0.27 |
Scored on dose accuracy, form, label transparency and third-party testing. Per-serving cost is list price divided by servings per container. No brand pays to be listed or ranked.
Common questions
How much L-Arginine should I take?
The typical range is 3-6 g daily in divided doses. Safe long-term
When should I take L-Arginine?
Before exercise or split through day. Optional.
Which form of L-Arginine is best?
Powder — Often in pre-workouts. Other forms in the catalog: Capsules, HCl salt, free base, alpha-ketoglutarate.
Is L-Arginine safe?
Commonly reported: GI upset, Diarrhea. Serious warnings: May reactivate herpes. Caution kidney disease
Which L-Arginine supplement scores highest?
Nootropics Depot AAKG 2, at 90/100. Scored on dose accuracy, form, label transparency and third-party testing — no brand pays to be listed or ranked.
Daily target & upper limit
3 g / dayL-Arginine has an established daily reference intake. See best forms, label synonyms, upper-limit warnings, and top-scoring supplements:
L-Arginine dosage reference →Primary uses
- Blood flow
- Exercise performance
- Cardiovascular health
- Erectile function
- Nitric oxide production
- Vasodilation and blood flow
- Sexual function (ED)
What systematic reviews concluded
Outcomes that systematic reviews of L-Arginine reached a verdict on: 5 with a benefit, 1 with no effect, 1 unclear. Each is quoted from a review and linked to it on PubMed. How these were read.
Reviews found a benefit (5)
“Oral l-arginine supplementation significantly reduces ABP.” PMID 42520885 · 2 reviews
“l-arginine supplements may improve cardiovascular function, ventilation, the serum level of lactate, and maximal oxygen consumption (VO2 Max) of football players.” PMID 39915258
“L-Arginine and the mix PLC + ALC appeared to be of some usefulness in improving erectile function, especially in combination with PDE5i in organic ED.” PMID 39279185
“Arg emerged as the most efficacious modality for reducing 100 m time.” PMID 39796467
“The complementary use of certain supplements (fatty acids, l-arginine, vitamin D3) can enhance the management of VOC and improve patients' physiological functions.” PMID 40022955
Reviews found no effect (1)
“Foods rich in polyphenols and nitrate provide trivial benefits for endurance exercise performance, although these effects may be food dependent.” PMID 34965876
Not enough to say: preeclampsia.
1 finding from reviews in specific patient groups (such as cancer, pregnancy or surgery) is not shown here.
How it works
- Converted to nitric oxide by NOS
- Vasodilation
- Growth hormone secretagogue
Dosage
- Typical range
- 3-6 g daily in divided doses
- Timing
- Before exercise or split through day
- With food
- Optional
- Duration
- Safe long-term
- Special populations
- Cardiovascular, athletes, ED
Forms
- Powder
- Capsules
- HCl salt· 70/100
- free base· 70/100
- alpha-ketoglutarate· 70/100
Safety
Common side effects
- GI upset
- Diarrhea
Contraindications
- Recent heart attack
- Active herpes
Products containing L-Arginine
Top-scoring supplements in our catalog that list L-Arginine on the label. Each product is graded on Formulate's ingredient-level rubric — dose accuracy, form, transparency, and third-party testing.
Evidence notes
Nitric oxide precursor
Grade B: Some human trials support key claims; further confirmation needed.
Cited research for L-Arginine
Clinical studies referenced across Formulate guides that mention l-arginine. Each links to the full study page with PubMed source + the guides that cite it.
L-Arginine compared head-to-head
Related in Amino Acid
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Medical disclaimer. This page is educational and does not replace advice from a qualified healthcare provider. Individual needs and risks vary — consult a professional before starting, stopping, or combining supplements, especially if you are pregnant or nursing, taking medication, or managing a health condition.