http://www.nhlbi.nih.gov/hbp/detect/detect.htm
National Heart, Lung, and Blood Institute, National Institutes of Health
You can find out if you have high blood pressure by having your blood pressure checked regularly. Most doctors will diagnose a person with high blood pressure on the basis of two or more readings, taken on several occasions. This page links to information about diagnosing high blood pressure, including how blood pressure is tested, tips for having blood pressure taken, categories for blood pressure levels in adults, and more.