L-arginine is an amino acid the body converts into nitric oxide, which relaxes and widens blood vessels. Its most dependable benefit is a modest lowering of blood pressure, with fair support for easing mild erectile difficulty. Other claimed effects are weak or unproven. A low-cost option, real but limited, with a few situations to avoid. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Blood pressure | <120/80 mmHg | Primary benefit and over-lowering safety check |
| Serum potassium | 4.0–4.5 mmol/L | Detects potassium elevation risk |
| eGFR | >90 mL/min/1.73m² | Screens kidney function before and during use |
| ADMA | <0.5 µmol/L | Predicts likelihood of response |
| hs-CRP | <1.0 mg/L | Tracks vascular inflammation context |
| Fasting glucose & HbA1c | <90 mg/dL; <5.4% | Context for metabolic goals |
| Triglycerides | <90 mg/dL | Context for any lipid goal |
Cadence: Baseline before starting; recheck blood pressure at 4 weeks and 8–12 weeks, then every 6–12 months during continued use; kidney function and potassium on a similar schedule in anyone with kidney concerns.