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Hypertension: how is it diagnosed?

Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 2 minutes read

Your blood pressure reading has two numbers, one 'above' the other - for example, 135/85. The higher number (called the systolic) is a measure of the pressure inside your arteries when your heart pumps blood out. The lower number (called the diastolic) is a measure of the pressure inside your arteries when your heart is resting between heartbeats. Blood pressure is measured in millimeters of mercury (mm Hg).

If you’re found to have high blood pressure (BP) on one occasion, you should make an appointment with your doctor or practice nurse to have this rechecked. It’s not diagnosed based on just one reading – they want to have a few. They will likely lend you a BP machine (or you may have one at home) and advise you to keep a BP diary, with a week of readings taken at different times of the day. Hypertension is diagnosed on what the majority of readings show.

A BP machine gives you a fraction number – if home readings are consistently over 140/90 mmHg, they may suggest starting treatment.

When should I get it checked?

Certain groups are at higher risk of developing hypertension. If you fall into one of the following categories, ask your doctor's office for a BP check or check it at your local pharmacy.

Age is the biggest risk factor, especially for those over 65. Those over 40 should request a physician check-up, including BP and a blood test for diabetes, high cholesterol, and kidney function. This is a one-and-done unless something is diagnosed, but you should have your BP checked at least every five years after age 40.

Who else is at risk?

Other high-risk groups include non-Hispanic black adults or those with a close family member diagnosed with high BP at an early age. Other factors include if you live in a deprived area, if you smoke, drink excess alcohol, or lots of coffee or other caffeinated drinks, if you are overweight, eating a diet high in salt, fats, and sugars and low in fruit and vegetables, or if you lead a high-stress lifestyle.

If any of these circumstances apply to you, you should get your BP checked.

Is treatment ever started immediately?

Treatment might be started before waiting for home BP readings if you are found to have very high BP, called severe hypertension. This is if your systolic BP (the top number) is 180 mmHg or higher or your diastolic is 110 mmHg or higher.

If you are not already on medication, you will be started then and followed up within a few days until an acceptable level is reached. Doctors are cautious to bring this down too quickly, so you will be closely monitored.

If you do not have severe hypertension, but your readings are high enough to need treatment then your doctor will advise you on lifestyle changes that will help reduce your BP as well as starting daily tablet medication to bring the level down.

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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