There is a form in front of you asking for a recent blood pressure. You have taken the same tablet for it for six years and nobody has changed anything about it. Last week the cuff at home gave you a number you had no idea what to do with, and nobody was in the room to ask. Get the technique right and one reading becomes something a clinician can use; learn three numbers and you can sort the readings that go on a form from the one that gets a phone call and the one that gets 911.
A reading counts when you have been sitting still for five minutes with your back supported, an empty bladder, nothing eaten or drunk for half an hour, both feet on the floor, the cuff on bare skin and your arm at chest height, and nobody talking. Take at least two readings a minute apart, in the morning and again in the evening before supper, and write them all down — the page asks for a daily record over five days rather than a single reading. On a reading above 180/120, wait five minutes and measure again; if the second one is also that high, it needs medical attention the same day. A cuff is one number among several a clinician reads together, and the ones drawn from blood keep their own schedule. Below 90/60 is low, and a run of low readings goes to whoever prescribes your tablet rather than into anything you settle on your own.
What makes a home reading usable
A usable reading is mostly made in the five minutes before the cuff inflates rather than while it is on your arm. The seven steps are: nothing to eat or drink for 30 minutes beforehand, an empty bladder, five minutes in a comfortable chair with your back supported, both feet flat with your legs uncrossed, your arm resting on a table at chest height, the cuff snug against bare skin rather than over a sleeve, and no talking while it runs. Take at least two readings, one or two minutes apart, at the same time every day.
Three of the seven do more work than they look like they do. Crossing your legs, or letting your arm hang at your side instead of resting it at chest height, pushes the number up, and so does caffeine, alcohol or a cigarette in the half hour before. A high number in a clinic room is also not always a high number: as many as 1 in 3 people with a high reading at the doctor's office may read normal outside it.
The device matters as well. Digital monitors are the best choice for home use for most people, they read less accurately if your body is moving while the cuff is on, and an irregular heart rate makes a reading less accurate again. Using yours once with your provider or nurse watching is the cheapest way to find out which of the seven you have been getting wrong.
Which reading is a phone call and which is 911
A reading above 180/120 is a phone call, and the same reading with any of six symptoms alongside it is 911. With no symptoms, NHLBI's instruction is to wait five minutes, check again, and call your healthcare provider if it is still that high — rather than giving it an hour to come down on its own.
The six are a sudden severe headache, difficulty breathing, sudden severe pain in the abdomen, chest or back, numbness or weakness, a sudden change in vision, and trouble talking. With any one of those, the five-minute recheck stops applying.
What happens to the tablet after a high reading belongs to the clinician who wrote the prescription, and to nobody at either end of that phone call but them. Your part of it is the number, the time you took it, and whether any of the six were present.
Readings that keep coming in low
Below 90/60 is low, and what a prescriber can act on is a run of them rather than one evening's number. Some people sit under that line permanently and always have. What changes the picture is low readings turning up where there were none before, or turning up with symptoms alongside — dizziness or lightheadedness, fainting, blurry vision, confusion, feeling tired or weak, headache, nausea, or a heart that feels like it is fluttering or racing.
Two causes of low blood pressure are ordinary in this situation: dehydration, and the medicines taken to control high blood pressure. Older adults more often run low as a side effect of those. Adjusting them belongs to the prescriber who wrote them, and what you carry to that person is a written record rather than a conclusion.
Body size and blood pressure are connected at the pump: a larger body may raise blood pressure because the heart has to work harder to supply every cell. That connection is why a reading can move while your weight is moving, in either direction, and why the person who prescribes for you wants the readings themselves rather than a description of them.
What makes a record usable is doing it identically each time: two readings a minute apart, morning and evening, for five days, then the whole set goes to your provider. Five days answers a question one evening cannot, which is whether last week was a reading or a pattern.
Low readings have their own emergency list. Cold and sweaty skin, rapid breathing, a blue skin tone, or a weak and rapid pulse are signs of shock, and those are 911 — in yourself, or in anyone else in the room.
| What the cuff shows | Where it goes |
|---|---|
| Under 120/80 | Normal for most adults. This is the one that goes on a form. |
| Below 90/60 | Low. A run of them goes to whoever prescribes your tablet. |
| Above 180/120, no symptoms | Wait five minutes and check again. Still that high, call your provider. |
| Above 180/120, with any of the six symptoms | Call 911. |
Make this week's readings count
- Empty your bladder, then sit with your back supported for five minutes, with nothing eaten, drunk or smoked in the half hour before.
- Bare arm, cuff snug, arm resting at chest height, feet flat, legs uncrossed, nobody talking.
- Take two readings a minute apart, morning and evening, and write down both numbers and the time.
- Do that for five days, then send the whole set to whoever prescribes your tablet — all of them, not the one that worried you.
- Put your most recent reading on the form, with the date you took it.
- Above 180/120 with a sudden severe headache, difficulty breathing, sudden severe pain in the abdomen, chest or back, numbness or weakness, a sudden change in vision or trouble talking, call 911.
Five days of readings, taken the same way at the same hours, is the one part of this that nobody but you can produce. It is worth more to the person who prescribes your tablet than any single evening's number, including the one that started this.
