The new definition of high blood pressure is 130/80 millimetres of mercury or greater: the first number represents the pressure on the blood vessels when the heart contracts, and the second is when the heart relaxes.
The old high blood pressure level was 140/90, which remains in place in other parts of the world like the UK and Australia, at least for the time being.
Experts say they want people to understand more about the complications that can occur at those lower numbers, and have also stressed the need for check-ups by qualified health professionals to get accurate readings.
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