L-Arginine Adult Dosing Recommendations
The recommended adult dosing of L-arginine varies significantly by indication, ranging from 4-8 g/day orally for cardiovascular conditions to 200-600 mg/kg/day intravenously for hyperammonemia in urea cycle disorders.
Dosing by Clinical Indication
Hyperammonemia (Urea Cycle Disorders)
For acute hyperammonemia, L-arginine hydrochloride should be administered intravenously 1:
Weight <20 kg:
- OTC/CPS deficiencies: 200 mg/kg over 90 minutes as bolus, then maintenance over 24 hours
- ASS/ASL deficiencies: 600 mg/kg over 90 minutes as bolus, then maintenance over 24 hours
Weight >20 kg:
- OTC/CPS deficiencies: 4 g/m² over 90 minutes as bolus, then maintenance over 24 hours
- ASS/ASL deficiencies: 12 g/m² over 90 minutes as bolus, then maintenance over 24 hours
Critical caveat: Arginine can cause hypotension, particularly when combined with hemodialysis; dose titration or reduction may be necessary 1.
Cardiovascular Conditions
Peripheral Arterial Disease (Intermittent Claudication)
Evidence suggests 8 g twice daily intravenously improved walking distance after 3 weeks 2. An oral food bar containing 3.3 g L-arginine (2 bars/day = 6.6 g total) showed modest improvement in pain-free walking distance after 2 weeks, though a larger trial was negative 2.
The evidence remains premature for firm recommendations in PAD 2, but if used, consider starting at 6-8 g/day orally.
Pulmonary Arterial Hypertension
For acute hemodynamic testing, 500 mg/kg infused over 30 minutes reduced mean pulmonary artery pressure by 15.8% and pulmonary vascular resistance by 27% 3.
For oral supplementation, 0.5 g/10 kg body weight acutely or 1.5 g/10 kg body weight per day for chronic therapy showed hemodynamic benefits 3. For a 70 kg adult, this translates to approximately 10.5 g/day.
Important limitation: Long-term efficacy data are lacking, and potential proproliferative effects via polyamines remain a concern 3.
Hypertension
Meta-analytic evidence supports blood pressure reduction with oral L-arginine 4, 5:
- Effective dose range: 4-9 g/day 4
- Doses >9 g/day showed no additional benefit 4
- Typical dosing: 4-24 g/day in clinical trials, with most using 4-8 g/day 5
- Divided dosing (at least twice daily) is recommended 4
The optimal dose appears to be 4-8 g/day for blood pressure reduction, with diminishing returns above 9 g/day 4.
Post-Acute Sequelae of COVID-19 (PASC)
For persistent chest pain with suspected microvascular dysfunction, 4 g twice daily may be considered 6. This represents a practical approach for endothelial dysfunction in the post-COVID setting.
Secondary Raynaud's Phenomenon
Divided dosing starting at 1-2 g/day, titrated up to 10 g/day based on response 7. This condition is associated with elevated asymmetric dimethylarginine (ADMA), making L-arginine supplementation mechanistically sound.
Note: L-arginine is ineffective in primary Raynaud's phenomenon, which lacks elevated ADMA 7.
General Supplementation and Safety
Maximum Safe Dose
Long-term supplementation up to 30 g/day for 90 days has been shown safe in healthy adults 8. A 30 g/day dose reduced systolic blood pressure and serum glucose in females, and decreased free fatty acids in both sexes without adverse events 8.
Conservative safe range: 3-8 g/day appears safe and avoids acute pharmacologic effects 9.
Microvascular Health
5 g/day for 14 days improved microcirculatory function in healthy young women and elderly women with and without type 2 diabetes 10. This dose decreased blood pressure in elderly women and improved vasoreactivity across all groups 10.
Pregnancy Complications
For hypertensive disorders or intrauterine growth restriction:
- <4 g/day for ≥1 month duration or during third trimester showed greater effects 11
- Intravenous administration more effective than oral for IUGR, but should be limited to <4 g/day 11
Practical Dosing Algorithm
For most adult indications:
- Start with 4-6 g/day divided into 2-3 doses (taken with meals to improve tolerability)
- Titrate up to 8-10 g/day if needed based on clinical response
- Maximum dose: 30 g/day (though most conditions respond to ≤10 g/day)
- Monitor for hypotension, especially in elderly or those on antihypertensive medications
Key contraindications and monitoring:
- Avoid in patients with recent myocardial infarction (one study showed higher mortality) 9
- Response may depend on baseline ADMA levels—L-arginine appears most effective when ADMA is elevated 9
- Monitor blood pressure, particularly with doses >10 g/day
- Consider divided dosing to minimize gastrointestinal side effects
The dose-response relationship is non-linear, with maximal benefits typically achieved at 4-10 g/day for most cardiovascular indications 4, 5.