L-Arginine
Pronunciation: el-AR-jih-neen.
- Generic name
- L-arginine
- Drug class
- Semi-essential amino acid; nitric oxide precursor. Sold as a dietary/food supplement (or, in Canada, a licensed Natural Health Product) in its general oral form; also the active ingredient of a genuinely separate FDA-approved prescription diagnostic injectable (R-Gene 10)
- Form
- Oral capsule, tablet, or powder (supplement form, strengths vary by product); separately, a 10% intravenous injection solution (R-Gene 10)
- Route
- Oral (general supplement form); intravenous (R-Gene 10 diagnostic injectable, physician-administered only)
- Legal status
- Dietary/food supplement (no prescription required) in its general oral form across all 6 markets reviewed; the separate injectable diagnostic product (R-Gene 10) is prescription-only and physician-administered
Availability and supply rules vary by country
Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand
Australia: L-Arginine (generic, multiple AUST L-listed brands) (8) · Full directory
What L-arginine is and how it works
L-arginine is an amino acid your body uses to make nitric oxide, a molecule that helps relax blood vessels. As a general oral product, it is sold as a dietary/food supplement, without the same premarket efficacy review that prescription medicines undergo. A separate, prescription-only injectable form (R-Gene 10) is used strictly by clinicians as a diagnostic test for growth hormone function. (3) (4)
Because L-arginine is sold as a supplement, it can be easy to assume it carries no real risk -- but genuine, clinically meaningful risks exist: a randomized clinical trial found increased deaths in people given L-arginine after a recent heart attack, and real interactions exist with common heart, blood pressure, and blood-thinning medicines. Talk to a doctor or pharmacist before starting L-arginine, especially if you take other medicines or have had a recent heart attack.
Mechanism of action: how L-arginine works
L-arginine is a semi-essential amino acid and substrate for nitric oxide synthase, producing nitric oxide (a vasodilator) and other downstream metabolites. This mechanism underlies both its studied cardiovascular/supplement-market uses and the VINTAGE MI trial's mortality signal, which is thought to relate to adverse vascular or inflammatory effects in the specific post-MI setting rather than a general toxicity of the amino acid itself. (3) (4)
What L-arginine is used for
General wellness/supplement use (oral form)
Sold as a dietary/food supplement for general wellness use, and studied in areas such as blood pressure, angina, and peripheral artery disease symptoms -- but these are supplement-market uses without the same regulatory efficacy review as an approved medicine, and evidence quality varies by condition. (1)
Diagnostic growth-hormone stimulation test (R-Gene 10, prescription injectable only)
Used by clinicians, given intravenously, to test how well the pituitary gland releases growth hormone -- for example, in the diagnostic work-up of suspected pituitary or growth-hormone-deficiency conditions. This is a physician-administered diagnostic procedure, not a self-directed treatment. (2)
Before taking L-arginine
Do not take / not appropriate for
- L-arginine supplementation is not recommended if you have had a heart attack recently -- a randomized clinical trial found a higher rate of death within 6 months in people given L-arginine after a recent heart attack compared with placebo. (all countries, oral supplement form) (3) (4)
- Avoid combining L-arginine with sildenafil or similar erectile-dysfunction medicines, or with nitrate medicines used for chest pain, without medical advice, since the combination may cause a dangerous drop in blood pressure. (all countries) (4)
Tell your clinician about
- Whether you have had a heart attack recently.
- Whether you have low blood pressure, or take blood-pressure-lowering medicines.
- Whether you take anticoagulant or antiplatelet (blood-thinning) medicines.
- Whether you have diabetes or take medicines that lower blood sugar.
- Whether you take potassium-sparing diuretics (such as amiloride, spironolactone, or triamterene).
- Whether you have asthma or allergic airway disease.
- Whether you have a history of cold sores or genital herpes.
- Whether you are pregnant or breastfeeding.
How to take L-arginine
- Follow the dose on the product label, or the amount recommended by your doctor or pharmacist -- supplement products vary in strength, so doses are not standardised the way a prescription medicine's dose is.
- If you are taking L-arginine alongside any prescription medicine (especially for blood pressure, heart disease, diabetes, or blood clotting), discuss this with your doctor or pharmacist first because of the real interactions described in this dossier.
- The prescription diagnostic injectable form (R-Gene 10) is given only by a clinician as part of a specific test -- it is never a product you take yourself.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6) (7) (8) (9)
Missed dose
If you miss a dose of an oral L-arginine supplement, simply take your next dose at its usual time -- do not take an extra dose. If you are taking it as part of a specific health plan recommended by a clinician, follow their guidance on missed doses.
Overdose
Very high doses of L-arginine can cause gastrointestinal symptoms such as nausea, cramping, and diarrhoea, and may worsen the blood-pressure and bleeding-related risks described in this dossier. Contact a doctor, pharmacist, or your local poison control service if you suspect you or someone else has taken a large excess amount. (4)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms.
Nausea, abdominal pain, and diarrhoea.
What to notice: Nausea, abdominal pain, and diarrhoea.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (4)
Bloating.
What to notice: Bloating.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (4)
Headache.
What to notice: Headache.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (4)
Gout (in susceptible individuals).
What to notice: Gout (in susceptible individuals).
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (4)
Allergic reactions.
What to notice: Allergic reactions.
What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (4)
Serious warnings
Recent heart attack — high caution
Symptoms: Not a symptom to watch for -- this is a pre-existing-condition caution: a randomized clinical trial found more deaths within 6 months in people given L-arginine after a recent heart attack, compared with placebo.
Action: Talk to your doctor before starting L-arginine if you have had a heart attack recently -- L-arginine supplementation is not recommended in this situation. (3) (4)
Signs of very low blood pressure — moderate
Symptoms: Dizziness, light-headedness, fainting, or feeling unusually weak, especially if combined with nitrate medicines, sildenafil-type medicines, or blood-pressure medicines.
Action: Seek medical advice promptly -- continue or stop the combination only as directed by your doctor; this combination can cause a dangerous drop in blood pressure, and the risk is greatest if symptoms are severe. (4)
Signs of unusual bleeding or bruising — moderate
Symptoms: Unexplained bruising, nosebleeds, or bleeding that takes longer than usual to stop, especially if you take anticoagulant or antiplatelet medicines.
Action: Contact your doctor or pharmacist promptly for advice -- L-arginine may add to the bleeding-risk effect of these medicines. (4)
Cold sore or genital herpes outbreak — moderate
Symptoms: New or worsening cold sores or genital herpes symptoms after starting L-arginine.
Action: Discuss this with a doctor or pharmacist if you have a history of herpes simplex -- arginine intake is widely reported to be able to trigger outbreaks in people who carry the virus, though this evidence comes from consumer-health/secondary sources rather than a single major regulator statement. (5)
Interactions
- Nitrate medicines (for chest pain) combined with L-arginine may cause blood pressure to drop too low. (4)
- Sildenafil and similar PDE5-inhibitor erectile-dysfunction medicines combined with L-arginine may cause a dangerous, excessive drop in blood pressure. (4)
- L-arginine can add to the blood-pressure-lowering effect of antihypertensive medicines. (4)
- Anticoagulant and antiplatelet medicines combined with L-arginine may increase bleeding risk. (4)
- L-arginine may lower blood glucose, which is relevant if you take diabetes medicines and may need monitoring or dose adjustment. (4)
- Potassium-sparing diuretics (amiloride, spironolactone, triamterene) combined with L-arginine may raise the risk of high blood potassium (hyperkalaemia). (4)
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
Specific pregnancy safety data for general L-arginine supplementation was not detailed with high confidence in the sources reviewed for this dossier -- discuss use with a doctor or pharmacist if pregnant, rather than assuming supplement status means no risk. (1) (2) (3) (4) (5) (6) (7) (8) (9)
Breastfeeding
Specific breastfeeding safety data for general L-arginine supplementation was not detailed with high confidence in the sources reviewed for this dossier -- discuss use with a doctor or pharmacist if breastfeeding. (1) (2) (3) (4) (5) (6) (7) (8) (9)
Children
General supplement use in children was not specifically detailed in the sources reviewed for this dossier -- discuss with a pediatrician or pharmacist before giving L-arginine supplements to a child. (1) (2) (3) (4) (5) (6) (7) (8) (9)
Elderly
No specific age-based dose adjustment is described for the general supplement form in the sources reviewed, though older adults are more likely to be taking blood-pressure, heart, or blood-thinning medicines that genuinely interact with L-arginine. (1) (2) (3) (4) (5) (6) (7) (8) (9)
Hepatic_impairment
Not specifically detailed for the general supplement form in the sources reviewed for this dossier -- discuss with a doctor if you have significant liver disease. (1) (2) (3) (4) (5) (6) (7) (8) (9)
Renal_impairment
Not specifically detailed for the general supplement form in the sources reviewed for this dossier -- discuss with a doctor if you have significant kidney disease, since arginine is a nitrogen-containing amino acid handled by the kidneys. (1) (2) (3) (4) (5) (6) (7) (8) (9)
Source_ids
US-MAYOCLINIC-LARGININE-SAFETY-2026 (1) (2) (3) (4) (5) (6) (7) (8) (9)
Monitoring
Before starting
- Recent heart attack history
- Current blood pressure and heart/blood-pressure medicines
- Anticoagulant/antiplatelet medicine use
- Diabetes medicine use
- History of herpes simplex
During treatment
- Watch for symptoms of low blood pressure (dizziness, fainting) if combined with nitrates, PDE5 inhibitors, or blood-pressure medicines.
- Watch for unusual bruising or bleeding if you take anticoagulant/antiplatelet medicines.
- Monitor blood glucose more closely if you have diabetes and are taking blood-glucose-lowering medicines.
Storage
Store the oral supplement as directed on its product label, typically at room temperature away from moisture and out of reach of children.
Professional information
Clinician-facing context only, sourced from the sources listed in this dossier; verify against current product labelling and clinical literature before advising patients.
United States, United Kingdom, European Union, Canada, Australia, New Zealand
Indication: General oral supplement use
Dose summary: No single regulator-set dose -- varies by product and manufacturer; typical studied ranges in the literature span roughly 2-20 g/day depending on the condition studied, but these are research doses, not an approved label dose.
Renal context: Not specifically detailed in the sources reviewed for this dossier -- arginine is a nitrogen-containing amino acid cleared partly via renal handling of urea-cycle byproducts. (1)
United States (prescription diagnostic use only)
Indication: Growth-hormone stimulation diagnostic test (R-Gene 10)
Dose summary: 30 g arginine hydrochloride (300 mL of R-Gene 10) infused intravenously for patients >=60 kg, per a defined diagnostic test protocol.
Renal context: Not specifically detailed in the sources reviewed for this dossier for the diagnostic-use product. (2)
Hepatic guidance
Not specifically detailed for the general supplement form in the sources reviewed for this dossier.
Overdose note
Very high doses are generally associated with gastrointestinal symptoms; manage supportively, with attention to blood pressure if combined with vasodilating or antihypertensive medicines. (3) (4)
Frequently asked questions
Is L-arginine safe to take after a heart attack?
No -- a randomized clinical trial (VINTAGE MI) found that people given L-arginine after a recent heart attack had more deaths within 6 months than those given placebo, and enrollment was stopped early because of this safety concern. L-arginine supplementation is not recommended after a recent heart attack; talk to your doctor. (3)
Is L-arginine regulated the same way as a prescription medicine?
No. The general oral form is sold as a dietary/food supplement (or, in Canada, a licensed Natural Health Product) in all 6 markets reviewed, meaning its specific health claims are not reviewed by regulators the way a prescription medicine's claims are. A separate, genuinely different product (R-Gene 10, an injectable) is FDA-approved as a prescription diagnostic test aid, used only by clinicians. (1) (2)
Can L-arginine interact with my other medicines?
Yes. Real interactions exist with nitrate medicines and sildenafil-type medicines (risk of excessive low blood pressure), blood-pressure medicines, anticoagulant/antiplatelet medicines (bleeding risk), diabetes medicines (blood sugar), and potassium-sparing diuretics (high potassium risk). Tell your doctor or pharmacist about all your medicines before starting L-arginine. (4)
What is the mechanism of action of L-arginine?
L-arginine is a semi-essential amino acid and substrate for nitric oxide synthase, producing nitric oxide (a vasodilator) and other downstream metabolites. This mechanism underlies both its studied cardiovascular/supplement-market uses and the VINTAGE MI trial's mortality signal, which is thought to relate to adverse vascular or inflammatory effects in the specific post-MI setting rather than a general toxicity of the amino acid itself. (3) (4)
What class of drug is L-arginine?
L-Arginine is classed as: Semi-essential amino acid; nitric oxide precursor. Sold as a dietary/food supplement (or, in Canada, a licensed Natural Health Product) in its general oral form; also the active ingredient of a genuinely separate FDA-approved prescription diagnostic injectable (R-Gene 10). (1) (2)
References
- L-Arginine dietary supplement product labels (various manufacturers) -- DailyMedU.S. National Institutes of Health / DailyMed (dietary supplement facts labels, various manufacturers) · United States · accessed 2026-07-30 · source 1
- R-GENE 10 (arginine hydrochloride) Injection, USP -- full prescribing informationU.S. Food and Drug Administration / DailyMed, full prescribing information, Pfizer · United States · accessed 2026-07-30 · source 2
- L-Arginine Therapy in Acute Myocardial Infarction: The Vascular Interaction With Age in Myocardial Infarction (VINTAGE MI) Randomized Clinical TrialPeer-reviewed randomized controlled trial (Schulman SP et al.), published in JAMA · United States (multi-centre trial, applies globally) · accessed 2026-07-30 · source 3
- L-arginine -- Mayo Clinic drug/supplement informationMayo Clinic (secondary clinical-safety reference, consolidating drug-interaction and caution data) · United States · accessed 2026-07-30 · source 4
- L-arginine and herpes simplex virus outbreak risk -- consolidated secondary sourcesSecondary consumer-health/clinical-summary sources (multiple, consistent) · United States (general, not country-specific) · accessed 2026-07-30 · source 5
- NATURAL HEALTH PRODUCT L-ARGININE monographHealth Canada, Natural and Non-prescription Health Products Directorate (NNHPD), Natural Health Product monograph · Canada · accessed 2026-07-30 · source 6
- Food supplements regulatory framework (Directive 2002/46/EC; UK post-Brexit retained framework)UK Food Standards Agency / EU Directive 2002/46/EC food-supplements framework · United Kingdom and European Union · accessed 2026-07-30 · source 7
- L-Arginine -- Australian Register of Therapeutic Goods (listed complementary medicine entries)Therapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-30 · source 8
- Regulation of Dietary Supplements in New ZealandMedsafe (New Zealand regulator) · New Zealand · accessed 2026-07-30 · source 9
Brand names by country
Single-ingredient L-arginine names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
United Kingdom
- L-Arginine (generic, multiple supplement brands) (7)food supplement framework confirmed · varies by product · various
Canada
- L-Arginine (generic, multiple NPN-licensed brands, e.g. Natural Factors) (6)Health Canada NHP licensed confirmed · varies by product · various NPN holders
Australia
- L-Arginine (generic, multiple AUST L-listed brands) (8)TGA ARTG listed complementary medicine confirmed · varies by product · various ARTG sponsors
New Zealand
- L-Arginine (generic, multiple supplement brands) (9)dietary supplements regulations 1985 confirmed · varies by product · various
View brands in additional countries.
European Union
L-Arginine (generic, multiple supplement brands per member state) (7)