A blood pressure reading has two numbers. The first (systolic) is the pressure as the heart pushes blood out. The second (diastolic) is the pressure as the heart relaxes between beats. Both are measured in millimetres of mercury (mmHg).
Measuring at home accurately
- Sit quietly for five minutes first. No coffee, cigarettes or exercise for 30 minutes before.
- Sit with your back supported, feet flat on the floor and legs uncrossed.
- Rest your arm on a table so the cuff is level with your heart.
- Use the correct cuff size — a cuff that is too small reads high.
- Take two or three readings a minute apart and record them all, with the date and time.
What the readings mean
A single high reading is not a diagnosis; blood pressure moves through the day. What matters is the pattern over time, which is why keeping a written or app-based record to show your clinician is so useful.
When to seek help
See a clinician promptly if your readings are consistently high, and seek urgent care if a very high reading comes with chest pain, breathlessness, severe headache, visual changes or weakness on one side of the body.
Our pharmacist can show you how to use a home monitor correctly when you buy one.