High blood pressure does not always cause symptoms, even when it is high enough to be a medical emergency. Checking your numbers is the only true way to know what your blood pressure is. If you have been diagnosed with high blood pressure or your doctor is concerned about your levels, you may be asked to check it at home with a blood pressure cuff, or your health care provider may use ambulatory monitoring (where you wear a device that checks your levels every 20-30 minutes throughout the day and night).