L-Arginine
An amino acid precursor to nitric oxide, studied for circulation.
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What it is
L-arginine is an amino acid the body converts to nitric oxide, which relaxes blood vessels. It's used for circulation and exercise, though citrulline often raises arginine levels more reliably.
How it works
L-arginine is an amino acid the body converts to nitric oxide, which relaxes blood vessels and supports blood flow. That vascular role is the basis for its use in circulation and exercise — though it's broken down quickly, which limits its effect compared with citrulline.
What it's been studied for
Taken to support blood flow, blood pressure, and exercise performance.
What the evidence shows
Evidence is mixed. Some studies show modest blood-pressure or circulatory benefits, but arginine is broken down quickly, which is why L-citrulline is often preferred for raising nitric oxide.
Who should consider it
It's used to support blood flow, blood pressure, and exercise. Evidence is mixed, and people who've had a heart attack should avoid high doses. Citrulline is often preferred for raising nitric oxide.
Amounts commonly studied
Studies use a wide range, often several grams per day in divided doses.
How to take it
Studies use a wide range, often several grams per day in divided doses. It may cause digestive upset and can lower blood pressure.
Forms & absorption
L-arginine powder or capsules; citrulline is an alternative for the same goal.
Food sources
Meat, poultry, fish, dairy, nuts, seeds, and legumes.
Safety & interactions
May cause digestive upset and can lower blood pressure. Use caution with blood-pressure medication, and people who have had a heart attack should avoid high doses, as one trial raised safety concerns.
Myths & what it won't do
Myth: arginine is the best nitric-oxide booster. Reality: it's cleared quickly, and L-citrulline often raises blood arginine more effectively. Myth: it's risk-free. Reality: use caution with blood-pressure medication, and people post-heart-attack should avoid high doses.
Common questions
- Arginine or citrulline?
- Citrulline often raises blood arginine and nitric oxide more reliably, since arginine is broken down quickly — many prefer citrulline for that goal.
- Does it lower blood pressure?
- It can, via nitric oxide, so use caution alongside blood-pressure medication.
- Who should avoid it?
- People who've had a heart attack should avoid high doses, as one trial raised safety concerns.
The amounts listed here are what published research has used — not a prescription or a recommended dose for you. Confirm anything you plan to take with your own healthcare provider, especially if you take medications, are pregnant or nursing, or have a health condition.
Related goals
Research on L-Arginine
Recommendations on this page are informed by published research. This is educational information, not medical advice.
- 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. View study →Note: Found oral L-arginine lowered blood pressure by about 5/3 mmHg across small trials (387 people in total).