L-arginine is an amino acid that helps the body build protein.
Your body usually makes all the L-arginine it needs. L-arginine is also found in most protein-rich foods, including fish, red meat, poultry, soy, whole grains, beans and dairy products.
As a supplement, L-arginine can be used orally and topically.
Because L-arginine acts as a vasodilator, opening (dilating) blood vessels, many people take oral L-arginine to try to treat cardiovascular conditions and erectile dysfunction.
Research on the use of L-arginine for specific conditions shows:
- Angina. Studies suggest that L-arginine might decrease symptoms and improve quality of life in people with a mild to severe form of this type of chest pain.
- High blood pressure (hypertension). Some research has shown that oral L-arginine can lower blood pressure in healthy people and people with a type of high blood pressure that affects the arteries in the lungs and the right side of the heart (pulmonary hypertension). Infusions of L-arginine also appear to reduce blood pressure in people with hypertension.
- Erectile dysfunction. Taking oral L-arginine might improve sexual function in men with erectile dysfunction due to a physical cause.
Using L-arginine orally or topically is generally considered safe.
Oral use of L-arginine might cause:
- Abdominal pain
- Allergic response
- Airway inflammation or worsening of asthma symptoms
L-arginine isn't recommended after a heart attack due to concerns that the supplement might increase the risk of death.
L-arginine can worsen allergies or asthma. Use the supplement with caution if you have these conditions.
Be careful about taking L-arginine if you've had cold sores or genital herpes. Too much L-arginine in your system can potentially trigger the virus that causes those conditions.
Possible interactions include:
- Anticoagulants and anti-platelet drugs, herbs and supplements. These types of drugs, herbs and supplements reduce blood clotting. Taking L-arginine with them might increase the risk of bleeding.
- Blood pressure drugs, herbs and supplements. L-arginine might reduce blood pressure in people who have high blood pressure. Combining use of L-arginine with a blood pressure drug, herb or supplement might increase the risk of blood pressure becoming too low.
- Diabetes drugs, herbs and supplements. L-arginine might decrease blood sugar levels in people with diabetes. If you're taking diabetes drugs, herbs or supplements, your dosage might need to be adjusted.
- Isoproterenol. Use of this heart medication with L-arginine might cause your blood pressure to become too low.
- Nitrates. Use of this chest pain medication with L-arginine might cause your blood pressure to become too low.
- Water pills (potassium-sparing diuretics). Don't take amiloride (Midamor), spironolactone (Aldactone) or triamterene (Dyrenium) with L-arginine. These medications can increase potassium levels, increasing the risk of developing a higher than normal level of potassium in your blood (hyperkalemia).
- Sildenafil (Viagra). Use of this erectile dysfunction medication with L-arginine might cause your blood pressure to become too low.