It's a change that could affect millions of people in Great Britain and also Americans patients too.
The British National Institute for Health and Clinical Excellence has adopted guidelines that involve taking repeated blood pressure readings over a 24-hour period , rather than one blood pressure check during a doctor's visit.
The group says it's the most cost effective way of deciding who should be prescribed drugs for hypertension.
The study appears in The Lancet.
Hypertension is usually based on blood pressure measurements in a clinic. Experts say in-office readings can artificially raise blood pressure due to nerves from what's known as the "white coat" effect.