How Hypertension Is Diagnosed

Hypertension (high blood pressure) is diagnosed when two or more blood pressure readings measure above 129 mmHg systolic or above 79 mmHg diastolic.

Blood pressure is measured using a blood pressure cuff and sphygmomanometer. This non-invasive device detects the pressure inside your arteries. Your healthcare provider may also use lab tests or imaging tests to diagnose some of the causes or complications of hypertension.

This article discusses how hypertension is diagnosed. It describes how blood pressure is measured and how to ensure accurate results. It also explains the different numerical ranges for hypertension and steps to take to lower high blood pressure.

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How Is Blood Pressure Measured?

Blood pressure is measured using a blood pressure cuff and digital or manual sphygmomanometer.

The cuff is placed around your upper arm and inflated, causing it to become tight and restrict arterial blood flow. The air is then released from the cuff and a sensor or stethoscope measures the pressure at its highest and lowest points.

Blood pressure is measured in millimeters (mm) of mercury (Hg). It is written out as two numbers:

  • Systolic pressure: The top number is the maximal pressure. This occurs at the moment your heart beats.
  • Diastolic pressure: The bottom number is the lowest pressure. This occurs when your heart relaxes between beats.


Your provider may take two or blood pressure readings at least five minutes apart. Readings may be taken on both arms.

If the readings vary by more than 5 mmHg, further readings may be done until closer readings are obtained. The purpose is to get a consistent reading, not to average widely ranging measures. 

A diagnosis of hypertension usually requires two or more elevated blood pressure readings taken at separate times.

How to Get an Accurate Reading

Blood pressure fluctuates from minute to minute during the course of the day. One reading at your healthcare provider's office is a snapshot of one moment in time. Activity, caffeine, stress, and anxiety can all cause a temporary rise in blood pressure.

To get the most accurate reading, your blood pressure should be taken in a quiet, warm environment. Sit quietly with your feet supported for at least five minutes before taking a reading. This is known as a resting blood pressure reading, which is considered the most accurate.

Before the Test

Avoid the following for at least 30 minutes prior to taking the test:

  • Drinking coffee or other caffeinated beverages
  • Exercising or being active, such as taking the stairs in the doctor's office
  • Smoking cigarettes or using other tobacco or nicotine products

Prior to taking your blood pressure, you should use the bathroom. If you are wearing long sleeves, your healthcare provider may have you uncover your arm above the elbow.

During the Test

The following can help to ensure an accurate reading during the test:

  • Do not talk.
  • Keep your feet flat on the floor, and do not cross your legs or ankles.
  • Rest your arm on a table and keep it relaxed.
  • Take slow deep breaths.

Make sure the blood pressure cuff fits correctly. A cuff that is too big or too small could cause an inaccurate reading.

What Levels Are Considered High?

Hypertension is diagnosed after two or more elevated blood pressure readings taken at least a week apart.

  • Normal blood pressure: Systolic pressure less than 120 mmHg and diastolic pressure less than 80 mmHg
  • Elevated blood pressure: Systolic pressure greater than 129 mmHg or diastolic pressure greater than 79 mmHg

Clinical hypertension is categorized into two stages:

  • Stage 1 hypertension: Systolic pressure of 130 mmHg to 139 mmHg or diastolic pressure of 80 mmHg to 89 mmHg
  • Stage 2 hypertension: Systolic pressure greater than 139 mmHg or diastolic pressure greater than 89 mmHg

Dangerously high blood pressure readings are:

  • Hypertensive urgency: Systolic blood pressure greater than 220 mm Hg and diastolic blood pressure greater than 120 mmHg without major symptoms
  • Hypertensive emergency: Systolic blood pressure above 180 mmHg or a diastolic pressure above 120 mmHg with signs of organ failure, such as dizziness, confusion, and shortness of breath

What Is White Coat Hypertension?

Some people have elevated resting blood pressures in the healthcare provider's office but have normal resting blood pressures at other times.

This pattern has been called white coat hypertension, and it usually occurs due to anxiety. Repeat checks may be necessary if this occurs.

Hypertension Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

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Testing Blood Pressure at Home 

If you have hypertension, your doctor may recommend testing your blood pressure at home.

At-home blood pressure monitoring devices are accessible and easy to use. Many can record and keep track of your blood pressure readings; this is helpful to you as you monitor hypertension, but also potentially useful to your healthcare provider as he works to diagnose it from the outset.

Home Blood Pressure Monitoring (HBPM)

You can measure your own blood pressure at home, a process referred to as home blood pressure monitoring (HBPM). HBPM has become much easier and more accurate in recent years, and it is now a viable option for diagnosing hypertension and helping manage it once identified.

This is particularly helpful for those who experience white coat hypertension, as your blood pressure should be normal at home and readings taken in that setting can make it clear that in-office results are moot, rendering treatment unnecessary.

Furthermore, if you have fluctuating hypertension that requires treatment, home monitoring can pick that up even if your in-office blood pressure checks do not. 

HBPM uses easy-to-use, electronic blood pressure devices that are readily available and cost $40 to $50, though prices vary.

Ambulatory Blood Pressure Monitoring (APBM)

An ABPM device consists of a blood pressure cuff that is worn on the arm and attached to a recording device, which can be worn on a belt.

Remember, hypertension is most accurately determined by average blood pressure during an entire day. ABPM takes and logs blood pressure at 15-minute or 30-minute intervals over a 24- or 48-hour period. This means that the blood pressure fluctuations that normally occur in a day can be accounted for as your healthcare provider assesses your recorded average.

At the same time, if you have fluctuating hypertension, your healthcare provider would be able to pick that up using APBM because the measures span a longer time period than measures in the office.

The diagnosis of hypertension with ABPM has been well-validated and is more accurate for diagnosing stage 1 hypertension than a single visit to the healthcare provider’s office.

Other Tests

Blood pressure is very closely tied to heart and kidney function. Blood work, imaging studies, and other tests can assist in the diagnosis of hypertension and its associated causes and complications.

Blood Tests

Blood tests may be needed to determine if you have secondary hypertension due to a serious or treatable health condition. Blood tests that may be ordered to assist in the diagnosis of hypertension include:

  • Electrolyte levels
  • Blood glucose 
  • Thyroid function tests
  • Kidney function tests: blood urea nitrogen (BUN) and creatinine levels

Urine Tests 

Urine tests can help determine if diabetes, kidney failure, or illegal drugs are causing or contributing to high blood pressure.  

Electrocardiogram (EKG)

An EKG is a fairly simple and rapid test that assesses your heart rhythm. Heart rhythm abnormalities can cause high blood pressure. Likewise, hypertension can produce long-term changes that result in heart rhythm abnormalities. 

Echocardiogram

Your heart function can be examined using an imaging test that visualizes your heart as it moves. Excessively high blood pressure may produce changes that can be identified using echocardiography, and some heart function abnormalities can produce high blood pressure. 

Ultrasound

A test that is useful for evaluating the kidneys and the blood vessels, an ultrasound may be needed if your healthcare provider is concerned about certain aspects of your blood flow. For example, if your healthcare provider believes that you may have excessive narrowing in one or more of your blood vessels, this can be evaluated using an ultrasound. 

CT Scan or MRI

If your healthcare provider suspects a tumor as the cause of your high blood pressure, you may need to have an imaging test, such as CT scan or MRI, usually to evaluate the kidneys or adrenal glands. 

Follow-Up

If you have hypertension, your healthcare provider will want to monitor your blood pressure more frequently.

The first course of treatment is usually lifestyle changes to help bring your blood pressure down. These include: 

  • Changing your diet to eat more fresh fruits and vegetables and less salt, sugar, and saturated fat
  • Getting regular physical activity and exercise
  • Losing weight with a combination of diet and exercise
  • Quitting smoking

If these changes do not lower your blood pressure enough, your provider will likely prescribe medication.

Summary

Hypertension is diagnosed when you have two or more elevated blood pressure readings at least a week apart. Elevated readings mean the top number is 130 mmHg or greater, or the bottom number is 80 mmHg or higher.

Blood pressure is measured by taking a reading with a blood pressure cuff and digital or manual sphygmomanometer. To ensure accurate readings, do not smoke, drink coffee, or exercise for 30 minutes before the test.

Blood pressure readings should be taken after sitting quietly for five minutes. Keep your feet flat on the floor, relax your arm, and do not talk while having your blood pressure checked.

Your healthcare provider may also order additional tests, including blood work, a urinalysis, heart monitoring, and imaging studies. Hypertension is typically treated with lifestyle changes and medication.

Frequently Asked Questions

  • Does hypertension cause noticeable symptoms?

    No, hypertension does not usually cause noticeable symptoms. Rarely, people may experience dizziness, shortness of breath, headaches, and nosebleeds.

  • What are the risk factors for high blood pressure?

    Hypertension is more common as you age, especially in women, but men are more likely to have hypertension until age 45. Black and White people are more likely to have hypertension than people of Asian or Latin descent. Certain other preexisting conditions also increase your risk of hypertension, including kidney disease, diabetes, hormone conditions, and sleep apnea.

  • How do you prevent hypertension?

    Hypertension isn't always avoidable, but making healthy lifestyle choices will help prevent it. This includes not smoking, avoiding drugs and limiting alcohol, eating a lower-salt diet, managing stress, and getting regular exercise.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
Richard N. Fogoros, MD

By Richard N. Fogoros, MD
Richard N. Fogoros, MD, is a retired professor of medicine and board-certified in internal medicine, clinical cardiology, and clinical electrophysiology.