Biomarker
Blood pressure: what systolic and diastolic numbers mean
Blood pressure is the force your circulating blood exerts against artery walls. It is written as two numbers — systolic over diastolic — and it is the single most modifiable input in almost every cardiovascular risk model.
What it measures
Systolic pressure is the peak as the heart contracts; diastolic is the resting pressure between beats. Both matter, but systolic pressure is the stronger predictor of cardiovascular events after roughly age 50, and it is the value that ASCVD, QRISK3 and SCORE2 all take as an input.
Reported in: mmHg
Reference ranges
Adult categories following the 2017 ACC/AHA classification.
Normal
Below 120 / below 80
No action beyond ordinary healthy habits and periodic rechecks.
Elevated
120–129 / below 80
Lifestyle change is recommended; recheck in 3–6 months.
Stage 1 hypertension
130–139 / 80–89
Hypertension by current thresholds. Treatment depends on overall 10-year cardiovascular risk.
Stage 2 hypertension
140+ / 90+
Medication is usually recommended alongside lifestyle change.
Hypertensive crisis
Above 180 / above 120
Seek medical care immediately, particularly with symptoms.
Laboratory reference ranges vary between analysers and populations. Always read the range printed on your own report.
What moves the number
- Dietary sodium, and the potassium-to-sodium balance of the whole diet
- Body weight and waist circumference
- Aerobic activity — even 30 minutes most days moves systolic pressure measurably
- Alcohol intake and sleep quality, including untreated sleep apnoea
- Chronic stress, caffeine timing and measurement technique
- Kidney function, thyroid disease and several common medications
How Vitals uses this measurement
Vitals flags any reading at or above 130/80, tracks the trend across every entry, and feeds your systolic value into the ASCVD, QRISK3 and SCORE2-Diabetes engines so you can see what a 10 mmHg reduction would actually do to your 10-year risk.
Frequently asked questions
Which number matters more, systolic or diastolic?
Both are used to classify hypertension, and the higher of the two categories decides your stage. In adults over about 50, systolic pressure predicts cardiovascular events more strongly because arteries stiffen with age.
How should I measure it at home?
Sit with your back supported and feet flat, arm at heart height, no caffeine or exercise for 30 minutes beforehand. Rest five minutes, then take two readings a minute apart and average them.
Is one high reading hypertension?
No. A diagnosis needs elevated readings on at least two separate occasions, and ideally home or ambulatory readings to rule out white-coat effect.
Related biomarkers
Sources
- Whelton PK et al. 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for High Blood Pressure in Adults
- World Health Organization, Hypertension fact sheet
Educational information only, not medical advice. Discuss your own results with a qualified healthcare professional.
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