In most cases, extensive tests are not needed to diagnose high blood pressure. If a blood pressure measurement shows your systolic and/or diastolic blood pressure is high, usually two more measurements at separate times will be done to confirm that you have high blood pressure.

Routine tests

A physical exam and a medical history are routinely used to evaluate high blood pressure. Additional blood tests and urine tests, such as urinalysis, also may be done before starting treatment to determine whether there has been damage to organs and to check for complications. These lab tests may include measurements of potassium, sodium (a component of salt), glucose (blood sugar), cholesterol levels, and tests to measure kidney function. Electrocardiogram (EKG, ECG) also may be done to determine whether there is any damage to the heart. Your doctor may want to check your risk of coronary artery disease.

In most people who have high blood pressure without any complications, routine lab test results will be normal. Sometimes, findings may suggest the presence of kidney disease, diabetes, or a hormone disorder.

If there is reason to suspect that blood pressure measurements taken in the doctor's office do not represent your accurate blood pressure (for example, if you may have white-coat hypertension), you may need to get your blood pressure measured away from the doctor's office.

In some cases, you may be asked to check your blood pressure at home 3 times a day and keep a record of the readings. If you are not able to measure your blood pressure accurately at home, you may need ambulatory blood pressure monitoring.

The U.S. Preventive Services Task Force recommended that people with high blood pressure or high cholesterol be routinely screened for diabetes. This recommendation is based on studies that show early detection and treatment of diabetes substantially decreases the risk of coronary artery disease in these people.⁷

Early detection

Screening tests and programs for high blood pressure vary widely in reliability. Results from automated blood pressure testing, such as you might do at a grocery store or pharmacy, may not be accurate. Any high blood pressure measurement discovered during a blood pressure screening program needs to be confirmed by a doctor or another health professional.

Rechecking blood pressure

The Seventh Joint National Committee (JNC 7) on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure recommends:¹

• Healthy adults with normal blood pressure (119/79 millimeters of mercury [mm Hg] or below) should have their blood pressure checked at least every 1 to 2 years. This can be done during any routine medical visit.
• Adults who are prehypertensive (120-139 and/or 80-89 mm Hg) should have their blood pressure checked as often as recommended by their doctor, or at least yearly. This can be done during any routine medical visit.
• Adults with other risk factors for heart or blood vessel disease or evidence of disease caused by high blood pressure need to have their blood pressure checked more often.