Systolic vs Diastolic: What Each Blood Pressure Number Means

Blood pressure is usually written as two numbers, such as 120/80 mmHg. The top number is systolic pressure. The bottom number is diastolic pressure.

What is systolic blood pressure?

Systolic blood pressure is the first, higher number. It measures the pressure in your arteries when your heart contracts and pushes blood around your body.

In a reading of 120/80 mmHg, the systolic number is 120.

What is diastolic blood pressure?

Diastolic blood pressure is the second, lower number. It measures pressure in your arteries when your heart relaxes between beats.

In a reading of 120/80 mmHg, the diastolic number is 80.

Does only the top number matter?

No. Both numbers matter.

A consistently raised systolic number can be important. So can a consistently raised diastolic number. Your GP or healthcare professional looks at the full reading, repeated measurements and your overall health risks before deciding whether action is needed.

Why your numbers can change

Blood pressure naturally moves up and down during the day. Exercise, anxiety, caffeine, alcohol, smoking, illness and some medicines can all affect it.

For a more reliable picture, take readings in similar conditions and record them consistently. Try to sit quietly for five minutes first and take two readings about a minute apart.

Make your readings easier to understand

Pulse lets you store systolic and diastolic readings together, so you can see trends rather than relying on memory. Start tracking your blood pressure with Pulse.