When diagnosing high blood pressure (hypertension), a physician will obtain a patient’s medical history. For example, the physician will ask whether high blood pressure runs in the family and what the patient’s dietary habits have been like (e.g., salt intake). A physician is also likely to perform a cholesterol test and glucose test, and to inquire about the patient’s level of activity.

The physician will perform a physical examination, which may include checking the patient’s blood pressure in both arms while standing and lying down. The American Diabetes Association recommends that people with diabetes have their blood pressure checked during every visit to a physician, or at least two to four times each year.

In some cases, the physician may ask patients to take their own blood pressure at home and bring in a daily log of blood pressure measurements. This strategy will help establish an individual’s normal blood pressure pattern and rule out “white coat hypertension” (blood pressure that is high only during a medical checkup, because of anxiety or stress). Another option may be ambulatory blood pressure monitoring, in which a patient wears a device that automatically assesses blood pressure, typically for 24 hours.

Blood pressure is measured by wrapping an arm cuff (attached to a monitor called 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 then pumped full of air until circulation is briefly cut off. Then some air will be slowly let out of the device, loosening the cuff’s grip on the arm and releasing the blood to flow freely again.

As the air is let out, the examiner watches the numbers coming down on a sphygmomanometer and waits until first hearing the heartbeat. 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 the heartbeat is last heard. 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 readouts.

Reliable blood pressure monitors are available if people are interested in monitoring their own blood pressure or that of their family members. When buying 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 against 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.

After the physical exam, a number of tests will often be ordered, which may include:

• Urinalysis and blood tests such as an electrolyte panel and waste product tests to rule out kidney diseases such as diabetic nephropathy.
  
  
• Electrocardiogram (EKG or ECG), which measures the heart’s electrical activity. By analyzing the results, a physician can check for heart problems that could be associated with high blood pressure, such as heart failure or left ventricular hypertrophy.
  
  
• Echocardiogram, which uses ultrasound waves to visualize the structures and functions of the heart. This test is also used to check for heart problems such as left ventricular hypertrophy.
  
  
• Chest x-ray to rule out an enlarged heart.

For patients who experience dizziness or fainting that may be due to sudden drops in blood pressure, which can result from dehydration or stress, a physician may recommend a tilt-table test. This test is conducted with the patient secured to a platform that pivots up and down.

Once a diagnosis has been made and serious problems such as kidney disease have been ruled out, then treatment can begin. However, very high or low blood pressure may require additional testing to rule out an unusual cause.