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Hypertension: how is it diagnosed?

Written by Healthwords's team of doctors and pharmacists based in UK | Updated: 29.03.2023 | 3 min read

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. High blood pressure is never diagnosed based on just one reading – several readings are needed and you may be lent a BP machine (or you may have one at home) and advised to keep a blood pressure diary, with a week of readings taken at different times of the day. Hypertension is diagnosed based on what the majority of readings show.

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 millimetres of mercury (mm Hg).

High blood pressure (hypertension) is viewed as blood pressure readings that are consistently at or above 140/90 mm Hg each time it is taken at the GP surgery, or if home or ambulatory readings are always more than 135/85 mm Hg.

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 surgery for a BP check or check it at your local pharmacy.

Age is the biggest risk, especially those over 65. Those aged over 40 can request a NHS Health Check which includes BP and a blood test for diabetes, high cholesterol and kidney function. This is a one-off, unless something is diagnosed, but you should have your BP checked as least every five years after the age of 40.

Who else is at risk?

Other high-risk groups include those who are black African or black Caribbean 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, eat 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 if your systolic BP is 180 mmHg or high 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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