Topic · Amino acid
L-arginine
L-arginine is a semi-essential amino acid your body makes and uses to produce nitric oxide, which helps blood vessels relax. The best evidence is for a modest drop in blood pressure at about 4 g/day or more; exercise and erectile function results are real but messier. Only about 20% of an oral dose reaches circulation, and most capsules contain far less than trial doses.
L-arginine FAQ
Does L-arginine lower blood pressure?
Probably a little, at gram-level doses. A 2022 meta-analysis of 22 randomized trials found an average drop of 6.40 mmHg systolic and 2.64 mmHg diastolic versus placebo, with an effect starting around 4 g/day and nothing extra above 9 g/day. That is a trial finding, not a treatment, so talk to your doctor about blood pressure.
How much L-arginine should you take a day?
No official RDA or upper limit exists, so trial doses are the best guide. Blood pressure trials landed around 4–9 g/day. Exercise trials used 1.5–2 g/day for several weeks, 10–12 g/day for eight weeks, or a single pre-workout dose of 0.15 g per kg. Many capsules hold only 500–1,000 mg, well below those amounts.
Does L-arginine improve workouts?
Maybe, but the proof is modest. A 2020 meta-analysis of 15 trials linked arginine to better aerobic and anaerobic performance, though results across the aerobic trials were inconsistent. The tested single dose was 0.15 g per kg of body weight, roughly 10–12 g for a 70 kg adult, taken 60–90 minutes before exercise.
Does L-arginine work for erectile dysfunction?
A 2024 network meta-analysis of 15 trials in about 1,000 men found L-arginine alone improved erectile function scores versus placebo. The catch: the trials were small and varied in dose and length. It is not a stand-in for a medical evaluation, and nitrates or sildenafil-type drugs call for a doctor's input first.
What are the side effects of L-arginine, and who should skip it?
Most often stomach trouble: nausea, cramping and diarrhea, mainly with single doses above 9 g. Doses of 3–6 g rarely caused problems, and splitting a large total helps. Blood pressure can also drop, so ask a doctor first if you run low, take blood pressure medication, are pregnant, nursing, under 18, or critically ill.