Arginine
Arginine is an amino acid the body can usually make itself and also gets from protein-rich foods. The body uses it to make nitric oxide.
Also listed as L-Arginine, Arginine HCl, L Arginine, L-Arginine HCl
What it is studied for
The strongest rated effects first. Bars show the size of the effect, the letter grades the evidence, and each rating lists the studies behind it.
Why is arginine linked to blood flow?
The body uses arginine to make proteins and nitric oxide, a molecule that relaxes blood vessels. That makes blood flow a plausible research target. It does not mean that adding more arginine will improve every activity that depends on circulation. 1 2
Key studies
The most recent publications linked to Arginine's ratings.
Why people take it
SuppCo community snapshot, 2026-09-28. Reasons for use are not evidence that it works.
Questions people ask
Is arginine the same as nitric oxide?
No. Arginine is a starting material the body uses to make nitric oxide. 1
Can it improve libido?
The erectile-dysfunction meta-analysis found no improvement in sexual desire, even though some erectile-function outcomes improved. 3
Is it suitable after a heart attack?
No. The VINTAGE MI trial found no heart-function benefit and a mortality imbalance that led to early closure. 2
Can I get it from plant foods?
Yes. Legumes, soy and nuts supply arginine; USDA also lists it in pumpkin seed kernels. 4 5
Should erectile problems simply be treated with a supplement?
Persistent erectile problems merit medical assessment because they can accompany cardiovascular disease. A supplement trial does not replace finding the cause. 4
Citrulline
Ornithine