NOW Sports · L-arginine · Powder
Is NOW Sports L-Arginine Powder underdosed?
Verdict
6 g per servingone dose · studies use 0.15 g/kg of l-arginine
Below research doseOne serving contains 6 g; studies use 0.15 g/kg (11.25 g at 75 kg) in one dose before training. The label's directions allow 1 serving a day. Studies dose it by bodyweight; this uses 75 kg.
One serving gives 6 g, so reaching the low end of what studies use (11.25 g) takes 1.9 servings at once; it ranks 1st of 17 L-arginine supplements here by dose.
To reach the research dose. It would take 2 servings at once, 12 g, to reach the 11.25 g at 75 kg studies use, more than the label's directions, which allow 1 serving a day.
What the label says
- L-Arginine per serving
- 6 g in 6 g of powder
- Servings a day
- 1 serving a day
- L-Arginine a day, as directed
- 6 g
- Research dose
- 0.15 g/kg Evidence: Weak
Suggested usage: Mix 2 level teaspoons daily as needed in at least 8 oz. of juice or water, preferably on an empty stomach.
More about l-arginine: forms, timing and the studies behind the dose.
Same category, compared
All 17 L-arginine supplements we checked, ranked by dose (commission never changes the order). Studies use 0.15 g/kg of l-arginine; servings counted to 11.25 g.
| Product | Per serving | Servings to reach it | Form |
|---|---|---|---|
| NOW Sports L-Arginine Powder (this product) | 6 g | 1.9 at once | Powders |
| Nutricost L-Arginine Powder | 5 g | 2.3 at once | Powders |
| Doctor's Best Pure L-Arginine Powder | 4.96 g | 2.3 at once | Powders |
| Micro Ingredients L-Arginine | 1.5 g | 7.5 at once | Tablets |
| NutraBio L-Arginine | 1.5 g | 7.5 at once | Powders |
| Pure Encapsulations L-Arginine | 1.16 g | 9.7 at once | Capsules |
| Puritan's Pride L-Arginine 1000 mg | 1 g | 11.3 at once | Capsules |
| Thorne L-Arginine | 1 g | 11.3 at once | Capsules |
| Best Naturals L-Arginine 1000 mg | 827 mg | 13.6 at once | Tablets |
| Havasu Nutrition L-Arginine Capsules + L-Citrulline | 827 mg | 13.6 at once | Capsules |
| Jarrow Formulas Arginine 1000 mg | 827 mg | 13.6 at once | Tablets |
| Nature's Bounty L-Arginine 1000 mg | 827 mg | 13.6 at once | Tablets |
| Source Naturals L-Arginine 1,000 mg | 827 mg | 13.6 at once | Tablets |
| NOW L-Arginine 700 mg | 700 mg | 16.1 at once | Capsules |
| Nutricost L-Arginine + L-Citrulline 750 mg | 500 mg | 22.5 at once | Capsules |
| Nutricost L-Arginine 500 mg | 500 mg | 22.5 at once | Capsules |
| Swanson L-Arginine 500 mg | 500 mg | 22.5 at once | Capsules |
Where the reference doses come from
- L-Arginine, 0.15 g/kg: Viribay et al., 2020.
- Label data: National Institutes of Health, Office of Dietary Supplements. Dietary Supplement Label Database, 2026. https://dsld.od.nih.gov/. Label 314470, including its servings a day.
For a supplement taken as one dose we judge one serving, and show the most the label allows in a day. Read the full methodology or the corrections log.