L-Arginine
Also known as Arginine, L-Arg
L-Arginine is a semi-essential amino acid and the primary substrate for nitric oxide (NO) synthesis. Nitric oxide dilates blood vessels, improving circulation and blood pressure. Its use in athletic performance has largely been superseded by citrulline, which raises arginine levels more efficiently, but arginine retains strong evidence for cardiovascular and erectile function.
Benefits
Raises nitric oxide and improves blood flow
ModerateAs the direct NO precursor, arginine supplementation increases nitric oxide, dilates blood vessels, and improves circulation.
Supports blood pressure
ModerateMeta-analyses show modest but consistent reductions in systolic and diastolic blood pressure with arginine supplementation.
Erectile function support
ModerateNitric oxide is the key signalling molecule behind penile erection; arginine at higher doses (3–6 g/day) has shown benefit in mild erectile dysfunction.
Pros & cons
Pros
- Direct nitric oxide precursor, clear mechanism
- Useful for cardiovascular and sexual health
- Widely available and inexpensive
Cons
- Citrulline raises blood arginine levels more effectively with fewer GI side effects
- High doses needed for performance benefits
- Not recommended after heart attack (one large trial showed harm)
Side effects
GI upset
Bloating, diarrhoea, and nausea are common at high doses.
May worsen herpes outbreaks
Arginine promotes herpes simplex virus replication; people prone to cold sores or genital herpes should be cautious.
Blood pressure drop
Can lower blood pressure significantly; caution with antihypertensives.
How to take it
Typical dose
3–6 g per day for cardiovascular/ED benefit; 6–10 g pre-workout for performance
Timing
30–60 minutes before exercise for performance; spread throughout the day for cardiovascular goals
Common forms
Tip: Consider L-Citrulline instead for workout pumps, it is better absorbed and raises arginine levels more effectively.
What the research says
[1]Arginine and blood pressure
ModerateMeta-analysis of RCTs shows arginine supplementation significantly reduces systolic and diastolic blood pressure.
Meta-analysis · 2022PubMed[2]Arginine and erectile dysfunction
ModerateSupplemental arginine (3–6 g/day) improves erectile function scores in mild to moderate ED in multiple controlled trials.
RCTs · 2019PubMed
How L-Arginine interacts
Synergies, absorption effects, and cautions between L-Arginine and other supplements in the matrix.
L-Arginine and its direct connections · click a node to open its guide
L-Citrulline converts to arginine in the kidneys far more efficiently than oral arginine; the two share the same nitric oxide pathway.
Compare the pairingVitamin C protects nitric oxide from oxidative breakdown, extending the vasodilatory effect of arginine.
Compare the pairingMagnesium supports vascular smooth muscle relaxation alongside nitric oxide from arginine.
Compare the pairingZinc is a cofactor for nitric oxide synthase, the enzyme that converts arginine to NO.
Compare the pairingFrequently asked questions
What is L-Arginine used for?
L-Arginine is most commonly used for heart health, energy, and recovery. As the direct NO precursor, arginine supplementation increases nitric oxide, dilates blood vessels, and improves circulation.
How much L-Arginine should I take?
A typical dose is 3–6 g per day for cardiovascular/ED benefit; 6–10 g pre-workout for performance. Consider L-Citrulline instead for workout pumps, it is better absorbed and raises arginine levels more effectively. Start at the lower end and confirm the right dose for you with a healthcare professional.
When is the best time to take L-Arginine?
Recommended timing: 30–60 minutes before exercise for performance; spread throughout the day for cardiovascular goals.
What are the side effects of L-Arginine?
Reported side effects include gi upset, may worsen herpes outbreaks, and blood pressure drop. Bloating, diarrhoea, and nausea are common at high doses.
Who should be careful with L-Arginine?
Do not use arginine after a heart attack, a large trial (VINTAGE MI) was stopped early due to increased mortality. Speak with a healthcare professional if any of these apply to you.
Important cautions
- Do not use arginine after a heart attack, a large trial (VINTAGE MI) was stopped early due to increased mortality.
- Caution with low blood pressure, antihypertensive medications, and Viagra/PDE5 inhibitors.
- May promote herpes simplex flares; consider pairing with lysine if prone.
More Amino Acids
5-HTP
A direct serotonin precursor for mood and sleep, use with care.
Collagen
The structural protein for skin, joints, and connective tissue.
Creatine
The most-studied performance and cognition supplement.
Compare L-Arginine with
Weighing your options? See how L-Arginine stacks up against similar supplements.