L-arginine (AHR-jih-nene) is a substance that's available in supplements, and is plentiful in foods such as nuts, red meat and dairy products. Some people take L-arginine because it can widen your arteries. It's thought that perhaps this widening might help lower your blood pressure. However, there's no evidence this is true.
Your body usually makes all the L-arginine it needs, and taking a supplement is rarely necessary.
L-arginine supplements can interact with some medications, including nitroglycerin and high blood pressure medications such as angiotensin-converting enzyme (ACE) inhibitors. People who have had cold sores or genital herpes also shouldn't take L-arginine supplements, because having too much L-arginine in your system can trigger the virus that causes those conditions.
If you want to reduce your blood pressure, talk to your doctor about treatment options, including healthy lifestyle changes. If you have high blood pressure, talk to your doctor before starting any new herbal or nutritional supplements.