Take readings of your blood pressure at the same time each day, and maintain a diary of your readings including the day, results and the time of the test, according to the American Heart Association. Let your doctor know if you have several elevated readings in a row.
Measure the blood pressure on both arms for the first few readings, and then continue monitoring on the arm that usually produces the higher results. Use a tailor's tape to measure the circumference of your upper arm, and select a monitor that has an appropriately sized cuff. Abstain from exercising, drinking caffeine or smoking for at least 30 minutes before testing blood pressure. Sit with your back supported and straight, legs uncrossed, and feet flat on the floor, resting your testing arm on a table with your upper arm at the level of your heart, notes the American Heart Association.
Take multiple readings, waiting a minute between each test. Write down all of the figures. Put your results into a diary to monitor your blood pressure over time. Some monitors come with memory to keep your readings automatically, so if you have one of those and prefer that sort of record storage, take that device with you to your appointments. If several consecutive days bring readings above 120 over 80, talk to your doctor about possible remedies, reports the American Heart Association.