Nitroglycerin(nye troe GLI ser in) is a type of vasodilator. It relaxes blood vessels, increasing the blood and oxygen supply to your heart. This medicine is used to relieve chest pain caused by angina. It is also used to prevent chest pain before activities like climbing stairs, going outdoors in cold weather, or sexual activity. This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.