L-Arginine
EVIDENCE: MODERATEAlso sold as: arginine, L-arginine base, arginine HCl, arginine AKG
Arginine is the amino acid the body uses to make nitric oxide, which relaxes blood vessels. Trials at 4–24 g a day lowered blood pressure slightly, and an 18-month trial at 6.4 g a day helped more people with prediabetes return to normal glucose tolerance.
Compiled by iSupplementReviews editorial team ·Researched 2026-10-16 · 3 sources
- Type
- Amino acid
- Studied dose
- 4–24 g/day (blood pressure); 6.4 g/day (glucose tolerance)
- Best form
- L-arginine base or HCl
- Our rating
- MODERATE — Several human trials — limits in size, duration, or independence
What is L-arginine?
L-arginine is an amino acid the body turns into nitric oxide, a signal that widens blood vessels. It is sold for circulation, blood pressure and exercise.
Other names and forms
Arginine, L-arginine base, arginine HCl, arginine alpha-ketoglutarate. L-citrulline is a related amino acid that raises blood arginine more efficiently.
Where does L-arginine come from?
Meat, fish, dairy, nuts and beans, plus the body’s own production.
How does L-arginine work in the body?
Arginine feeds the enzyme that makes nitric oxide. Extra arginine may help when nitric oxide production is impaired, as in some people with metabolic syndrome.
What is L-arginine claimed to do?
Improve blood flow, lower blood pressure, support blood sugar and erections.
What does the research show?
| Claim | Evidence | Dose studied | Verdict |
|---|---|---|---|
| Blood pressure | Meta-analysis of RCTs | 4–24 g/day | Small positive |
| Glucose tolerance in prediabetes | 18-month RCT + follow-up | 6.4 g/day | Mixed positive |
Blood pressure
Arginine lowered blood pressure by a few points in pooled trials. Dong et al. (2011) analyzed 11 randomized trials at 4–24 g a day and found average reductions of about 5.4 mmHg systolic and 2.7 mmHg diastolic.
Prediabetes
Arginine at 6.4 g a day did not prevent diabetes over 18 months but improved glucose tolerance. Monti et al. (2012) studied 144 people with impaired glucose tolerance and metabolic syndrome. Diabetes rates were similar, but about 42% on arginine versus 22% on placebo returned to normal glucose tolerance. A longer follow-up reported lower diabetes risk years later (Monti et al., 2018).
What dose was studied?
| Goal | Dose | Duration |
|---|---|---|
| Blood pressure | 4–24 g/day | 2–24 weeks |
| Glucose tolerance | 6.4 g/day | 18 months |
Side effects
Bloating, diarrhea, nausea at gram doses.
Drug interactions
- Blood-pressure drugs and nitrates: additive lowering (moderate).
- Erectile-dysfunction drugs (sildenafil and similar): additive (moderate).
- Diabetes medicines: may add to glucose effect (minor).
Who should not take L-arginine?
People who recently had a heart attack, and people prone to cold sores or herpes outbreaks (arginine may encourage viral replication).
What the authorities say
Arginine is a normal dietary amino acid; regulators do not approve it as a treatment. Clinical references advise caution after a heart attack.
What to know about L-arginine
Arginine’s blood-pressure and glucose effects appear at doses of several grams a day. Milligram amounts are far below the studied range.
Frequently asked questions about L-Arginine
Does arginine lower blood pressure?
Slightly. A meta-analysis of 11 trials using 4–24 g a day found average drops of about 5 mmHg systolic and 3 mmHg diastolic.
Does arginine help blood sugar?
In one long trial of people with prediabetes, 6.4 g a day for 18 months did not reduce diabetes cases but did help more people return to normal glucose tolerance.
Is arginine safe?
Usually, at several grams a day, though it can cause bloating and diarrhea. People with a recent heart attack or herpes outbreaks are often told to avoid it.
References
- [1]Dong JY 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)
- [2]Monti LD et al. — Effect of a long-term oral l-arginine supplementation on glucose metabolism: a randomized, double-blind, placebo-controlled trial (Diabetes Obes Metab, 2012)
- [3]Monti LD et al. — Decreased diabetes risk over 9 year after 18-month oral L-arginine treatment in middle-aged subjects at cardiovascular risk (Eur J Nutr, 2018)
Products we reviewed containing L-Arginine
Based on recorded labels or seller-described formulas. Inclusion does not establish a match to the strains, preparations or amounts studied here; check each review's disclosure limits.