The diagnosis for high blood pressure begins with the physician taking a patient’s full medical history. During the medical history, the physician will ask ask about heart-related problems in the family (e.g. high blood pressure, coronary heart disease). The physician will also question the patient about lifestyle habits, such as diet, exercise and stress.

After obtaining a thorough medical history, the physician will complete a physical examination, which will include checking the patient’s blood pressure in both arms while standing and lying down. In some cases, the physician may ask the patient to take his or her own blood pressure at home and provide a daily log of blood pressure measurements. This strategy will help establish the patient’s normal blood pressure pattern and rule out white coat hypertension (high blood pressure that is caused by anxiety from being in a physician’s office). It has also been shown that, in adults 65 years of age and older, blood pressure may drop somewhat in the first two hours after eating. This may result in an inaccurate blood pressure reading if taken during that interval. In addition, blood pressure readings may be affected if an individual drinks caffeine or smokes cigarettes 30 minutes before blood pressure is taken. Individuals also should go to the bathroom prior to the reading as a full bladder can change a blood pressure reading.

Typically, blood pressure is measured by wrapping an arm cuff (attached to a sphygmomanometer) snugly around the patient’s arm and then using a stethoscope to listen to the brachial artery located at the inside elbow on the same arm. The cuff is pumped full of air until circulation is very briefly cut off. Then some air will be slowly let out of the device, loosening the cuff’s grip on the arm and allowing the blood to flow freely again. As the air is let out, the examiner watches the numbers drop on a simple monitor (sphygmomanometer) and waits until a heartbeat is heard. The number at which that occurs is the systolic pressure. The examiner remembers this as the numbers continue to come down on the monitor and notes the number at which he or she last hears the heartbeat. The number at which that occurs is the diastolic pressure. Other blood pressure measurement devices may also be used. Some use mercury manometers to measure the pressure and others employ digital devices.

Reliable blood pressure monitors are available for people who are interested in monitoring their own blood pressure and/or that of their family members. When purchasing these monitors, it is important to consult with a physician or a consumer product-rating agency regarding the reliability of home monitors. Generally, arm cuff digital monitors are the easiest and most reliable to use but should be periodically checked with a mercury sphygmomanometer. Researchers are also testing 24-hour blood pressure monitors, with early studies focusing on patients with high blood pressure who are at increased risk for a heart attack.

According to the American Heart Association, automated blood pressure devices found in some public areas (e.g., drug stores) should generally not be considered reliable or accurate measuring devices. These machines are often poorly maintained and can return inaccurate results for large individuals.

Also, ambulatory blood pressure monitoring has revealed that in normal individuals, blood pressure is higher during the morning hours and drops at night (also called the dipping phenomenon). The absence of normal dipping is abnormal and has been associated with increased risk of cerebral and cardiac complications in patients with and without established hypertension.

Following the physical examination, a number of tests may be ordered, which include:

Once a diagnosis has been made and serious problems (e.g., kidney disease) have been ruled out, treatment can begin. However, very high blood pressure may require additional testing to rule out an unusual cause. For example, a renal Doppler sonogram or scan may be ordered to evaluate for high blood pressure related to kidney disease or caused by renal artery stenosis (narrowing). Also, a 24-hour urine test may be needed to rule out an endocrine disorder, such as Cushing disease or pheochromocytoma.

High blood pressure may occur in either adults or children. Some people may also be diagnosed with the opposite condition, low blood pressure (hypotension). Although some people with high blood pressure do not need to take medication providing they can control their risk factors (e.g., weight), most people will generally require long-term treatment with medications.