L-Arginine
What the evidence shows
The direct precursor to nitric oxide, the molecule PDE5 inhibitors (sildenafil, tadalafil) work downstream of — the mechanistic logic is sound, and some trials show erectile function improvement, particularly in men with mild-moderate ED. Oral bioavailability is a real limitation, which is part of why L-citrulline is often preferred (it converts to arginine more efficiently).
How it's thought to work
Direct substrate for nitric oxide synthase, which produces nitric oxide — the signaling molecule that relaxes penile smooth muscle and allows blood inflow during an erection.
Typical Dosage
3–6g/day, split into 2 doses given its short half-life and absorption limits.
Safety Notes
Can cause GI upset at higher single doses. Avoid combining with nitrate medications or PDE5 inhibitors without medical guidance due to additive blood-pressure-lowering effects.
Want the full clinical breakdown?
L-arginine is the direct precursor to nitric oxide — the molecule that enables erection. Here's the effective dosage, how long it takes to work, and how it compares to L-citrulline.
Read the full evidence reviewConsidering adding L-Arginine to your routine?
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