Blood pressure
The force blood exerts against artery walls, reported as systolic over diastolic.
Blood pressure is the force blood exerts against artery walls, reported as two numbers: systolic, the peak as the heart contracts, over diastolic, the trough as it refills. It is written in millimetres of mercury and it is arguably the most valuable number in preventive medicine.
It earns that status by being cheap, painless, strongly linked to outcomes and highly treatable. Raised blood pressure is a leading contributor to stroke, heart attack, kidney disease and vascular dementia, and lowering it reliably reduces those risks.
It is also almost entirely silent. There are no symptoms until something has gone badly wrong, which is why the only way to know yours is to measure it, and why national health check programmes prioritise it above far more glamorous tests.
Measurement technique changes the answer more than people expect. It should be taken sitting, back supported, feet flat, arm at heart height, after several minutes of quiet, with the correct cuff size and no talking. A rushed reading taken over a coat with your legs crossed can be tens of millimetres out.
One high reading is not a diagnosis. Blood pressure varies through the day, rises with stress and caffeine, and is famously elevated in clinics. Repeated readings at home, or ambulatory monitoring, are how the picture is actually established.
The levers are well established: reducing salt, losing excess weight, regular aerobic exercise, moderating alcohol, and medication where those are not enough. Exercise lowers it both acutely, for hours after a session, and chronically with training.
In practice, buy a validated upper arm monitor, measure properly, and take a persistently raised average to a GP. Our heart age calculator uses systolic pressure alongside your other numbers to estimate cardiovascular risk.