Diagnosing High Blood Pressure

Medically Reviewed by Brunilda Nazario, MD on September 20, 2021
4 min read

Hypertension, or high blood pressure, is often called a "silent disease" because you usually don't know that you have it. There may be no symptoms or signs. Nonetheless, it damages the body and eventually may cause problems like heart disease.

Therefore, it's important to regularly monitor your blood pressure, especially if it has ever been high or above the "normal" range, or if you have a family history of hypertension. The USPSTF recommends that all adults 18 years or older be screened for hypertension.

Blood pressure is most often measured with a device known as a sphygmomanometer, which consists of a stethoscope, arm cuff, dial, pump, and valve.

You can get your blood pressure measured by a health care provider, at a pharmacy, or you can purchase a blood pressure monitor for your home. Home blood pressure readings can be especially helpful in diagnosing and monitoring hypertension because they represent what is happening in the real world (rather than just at the doctor’s office). But before these numbers can be relied on for treatment decisions, it is important to bring the monitor in to your doctor’s office and have it checked against the office readings for accuracy. Blood pressure is recorded as two numbers: the systolic and diastolic pressures.

  • Systolic blood pressure is the maximum pressure during a heartbeat, when the heart is sending blood throughout the body.
  • Diastolic blood pressure is the lowest pressure between heartbeats, when the heart is filling with blood.

Blood pressure is measured in millimeters of mercury (mmHg) and is written systolic over diastolic (for example, 120/80 mmHg, or "120 over 80"). According to the most recent guidelines, a normal blood pressure is less than 120/80 mmHg.  Elevated blood pressure is 120 to 129 and less than 80. Hypertension is blood pressure that is greater than 130/80.

Blood pressure may increase or decrease, depending on your age, heart condition, emotions, activity, and the medications you take. One high reading does not mean you have high blood pressure. It is necessary to measure your blood pressure at different times, while you are resting comfortably for at least five minutes. To make the diagnosis of hypertension, at least three readings that are elevated are usually required.

In addition to measuring your blood pressure, your doctor will ask about your medical history (whether you've had heart problems before), assess your risk factors (whether you smoke, have high cholesterol, diabetes, etc.), and talk about your family history (whether any members of your family have had high blood pressure or heart disease).

If your doctor asks questions that sound embarrassing or overly personal, remember that the information you provide enables them to better establish a diagnosis, or to determine which treatment is most appropriate for you. Never fib in response to questions about alcohol or drug use, sexual history, or other lifestyle matters. Be honest about the extent to which you are taking your prescriptions or following a treatment plan. Withholding the truth can affect the quality of your care and can even lead to a wrong diagnosis.

Your doctor will also conduct a physical exam. As part of this exam, they may use a stethoscope to listen to your heart for any abnormal sounds or “murmurs” that could indicate a problem with the valves of the heart. Your doctor will also listen for a whooshing or swishing sound that could indicate your arteries are blocked.Your doctor may also check the pulses in your arm and ankle to determine if they are weak or even absent.

If you're diagnosed with high blood pressure, your doctor may recommend other tests, such as:

  • Electrocardiogram (EKG or ECG): A test that measures the electrical activity, rate, and rhythm of your heartbeat via electrodes attached to your arms, legs, and chest. The results are recorded on graph paper.
  • Echocardiogram: This is a test that uses ultrasound waves to provide pictures of the heart's valves and chambers so the pumping action of the heart can be studied and measurement of the chambers and wall thickness of the heart can be made.

You and your provider can work as a team to lower your high blood pressure. Here are some questions to ask so you can be fully informed.

  • What should my blood pressure be?
  • What kind of diet should I follow to help control my blood pressure?
  • How much should I weigh?
  • Can you recommend a diet or eating plan to help me reach that weight?
  • How much exercise should I be doing?

Then, if your doctor has prescribed blood pressure medication, ask:

  • How does this medication work?
  • Is it generic, and if not, are there generic substitutes available?
  • What are the side effects?
  • What interactions might happen with the other drugs I’m taking?
  • Is there a specific time of day that I should take the medication?
  • Should I take it with food or on an empty stomach?

Don't hesitate to use the words "I don't understand." Doctors are only human and may not always know when they haven't explained something well or in terms you can understand. Never feel embarrassed or shy about asking for clarification about something your doctor says.

When in doubt, repeat what your doctor has told you and ask if you've got it right. You can also ask if they recommend any specific reading materials about your condition.