High blood pressure is the most common serious condition that people carry for years without noticing. It does not hurt. It does not announce itself. It is found, when it is found, because somebody put a cuff on an arm.
What the two numbers are
The upper number, systolic, is the pressure in the arteries when the heart contracts. The lower, diastolic, is the pressure between beats. Both matter, and after roughly age 50 the systolic number carries more predictive weight. A single high reading is not a diagnosis; a pattern of them across days is.
How to take one properly
Sit for five minutes first, feet flat, back supported, arm resting at heart height. No coffee, cigarettes or exercise in the half hour before. Do not talk during the measurement — conversation alone can lift a reading noticeably. Take two readings a minute apart, morning and evening, for several days, and give your doctor the average rather than the worst one.
Home cuffs beat clinic cuffs for accuracy over time
Readings taken in a clinic are often higher than the same person's true average, an effect well documented enough to have a name. Home measurement over a week gives a better picture, provided the device is a validated upper-arm cuff. Wrist and finger devices are convenient and considerably less reliable.
Salt, alcohol and the two changes with the best evidence
Reducing sodium lowers blood pressure measurably in most people, and the majority of dietary sodium comes from packaged and restaurant food rather than the salt cellar. Cutting alcohol is the other change with a fast, visible effect. Both work within weeks, which makes them easy to test on yourself.
Movement, weight and sleep
Regular aerobic activity lowers pressure independently of weight loss, and around 150 minutes a week of moderate movement is the usual target. Losing even a modest amount of excess weight helps. Untreated sleep apnoea keeps pressure elevated overnight and is a common reason readings refuse to improve despite everything else being done properly.
Why circulation shows up elsewhere first
Arteries are not passive tubing. Their lining releases signals that tell vessels when to widen, and that responsiveness degrades quietly under years of high pressure or high blood sugar. Because the smallest vessels are affected earliest, changes in sexual function often appear before anything shows up on a treadmill test — which is exactly why doctors treat it as useful information rather than an embarrassing aside.
When to be seen
Chest pain or pressure, breathlessness on ordinary exertion, calf pain when walking that eases with rest, new leg swelling, or a home reading that is very high should be dealt with promptly rather than monitored at home.
If it has been more than a couple of years since anyone checked, that is the most useful thing on this page.