A blood pressure reading has two numbers. The top number (systolic) is the highest pressure, when your heart pumps. The bottom number (diastolic) is the lowest pressure, when your heart relaxes between beats. A reading of 130/80 means 130 over 80.
Your blood pressure changes through the day with what you are doing, so one reading is a snapshot rather than a verdict. This guide explains what the numbers mean. It can't tell you what your own numbers mean for you: that is a conversation for your doctor.
What counts as normal or high?
It depends on which guidance you read. The two below use different lines, so do not be surprised if a chart from another country looks different.
| Source | Normal | High |
|---|---|---|
| CDC (US) | Less than 120/80 | Consistently at or above 130/80 |
| NHS (UK), checked by a professional | Not stated on this page | 140/90 or higher |
| NHS (UK), checked at home | Not stated on this page | 135/85 or higher |
Your doctor may set a different target for you. Follow that rather than a general chart.
Why you can't go by how you feel
The CDC says most people with high blood pressure have no signs or symptoms, and that measuring it is the only way to know. Over time, high blood pressure can damage the heart, brain and kidneys, even when you feel fine.
Low blood pressure is different: the NHS says it can cause symptoms such as dizziness or fainting. If that happens to you, tell your doctor.
How to take a reading at home
If your doctor or nurse asks you to check at home, follow what they tell you. The NHS describes this routine:
- Sit down and rest your outstretched arm on a table.
- Take your blood pressure and note both numbers.
- Wait 1 minute and take it again.
- Usually do this 2 times, once in the morning and once in the evening, for as many days as your doctor or nurse says.
Follow the instructions that come with your machine, because they differ.
What to bring to your appointment
A written record of readings with the date and time is more useful than remembering a single number. If you take blood pressure medicine, your doctor may also ask whether you have been taking it as prescribed. An honest record helps with that. See what to bring to a specialist appointment.
If you take blood pressure medicine, do not stop or change it because of a single reading. Talk to your doctor or pharmacist first. If you have severe symptoms such as chest pain, get urgent medical help.
Frequently asked questions
Which number matters more?
Both are recorded because they measure different things. Your doctor will look at both of them, and at your readings over time.
Is 130/80 high?
Under the CDC's definition, a reading consistently at or above 130/80 is high blood pressure. Under the NHS's guidance, high starts at 140/90 when a professional checks it or 135/85 at home. Ask your doctor which applies to you.
Why does my reading change during the day?
The CDC says blood pressure changes through the day based on your activities. That is why your doctor looks at more than one reading.
Sources
About high blood pressure, CDC. Blood pressure test, NHS.
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