The 10-point gap that changes your diagnosis
In the UK, NICE and the British Hypertension Society follow the European ESC/ESH 2018 guidelines: high blood pressure starts at 140/90 mmHg. The range 130-139 / 85-89 is called "high-normal" and does not automatically require medication.
Under AHA 2017 guidelines used in the US, Stage 1 hypertension starts at 130/80. Applied to a UK population, this lower threshold would roughly double the number of people classified as hypertensive. The difference is not a minor technical detail -- it reflects a genuine debate about when to intervene with treatment versus lifestyle changes.
Check your numbers with the blood pressure tool, which displays results against both ESC/ESH and AHA classifications so you can see the difference directly.
Home monitoring: what the evidence shows
A single reading at a GP surgery can be misleading. "White coat hypertension" -- where readings are elevated in a clinical setting but normal at home -- affects an estimated 15 to 30 % of patients. Conversely, "masked hypertension" reads normal at the surgery but is elevated throughout the day.
NICE recommends home blood pressure monitoring with a validated device as standard practice before diagnosing hypertension. Take readings twice a day for at least 4 days, discard the first day, and average the rest. This is closer to the French "rule of 3" approach (3 readings morning and evening for 3 days) than to a one-off clinical measurement.
Why the same number can mean two different things
A reading of 135/85 is "high-normal" under ESC/ESH and "Stage 1 hypertension" under AHA. The number is identical; the clinical meaning differs. If you have read about blood pressure guidelines online -- particularly from US sources -- you may be comparing against the wrong thresholds for your country.
Blood pressure also varies through the day, with exercise, caffeine, and stress. A single isolated measurement has limited diagnostic value. Consistent home monitoring, combined with a GP review, gives a far more accurate picture of your cardiovascular risk.