Taking a specific amount of arginine supplement for just three days doesn’t change the levels of nitric oxide in the blood of highly trained male athletes when they do short, intense workouts.

Taking arginine supplements for just three days won’t make you stronger or more powerful during short, intense workouts like sprinting or lifting heavy weights—even if you’re already a well-trained athlete.

Taking L-arginine pills can raise the level of arginine in your blood, but that doesn’t always mean you’ll produce more nitric oxide or get better at exercising—sometimes it helps, sometimes it doesn’t.

Taking 6 grams of L-arginine might help healthy young men lower their blood pressure and increase a chemical in their blood that helps blood vessels relax.

Taking a specific supplement called L-citrulline every day for a week, plus a little more before working out, can boost a key chemical in your blood by about three-quarters — and that chemical helps your body make nitric oxide, which is good for blood flow.

Taking a daily L-arginine supplement for two weeks doesn't help lower ammonia levels in the blood when healthy young men cycle hard, because the supplement group and the placebo group ended up with pretty much the same ammonia levels.