Understanding Blood Pressure Numbers
What systolic and diastolic numbers mean.
What the Two Numbers Mean
A blood pressure reading is written as two numbers, one over the other. Each number measures something different about how your heart is working.
The Blood Pressure Categories
Once you have a reading, here’s what each range generally means:
正常
Systolic below 120 and diastolic below 80. In practice: keep up your regular check-ins.
升高咗
Systolic 120–129 and diastolic below 80. In practice: this is a signal worth acting on early. Small, sustained changes now (activity, sodium, sleep) can help keep it from progressing.
Stage 1 Hypertension
Systolic 130–139 or diastolic 80–89. In practice: worth discussing with your care team. Lifestyle changes are typically the first step, sometimes alongside medication depending on your overall risk.
Stage 2 Hypertension
Systolic 140 or higher or diastolic 90 or higher. In practice: your care team may recommend starting treatment, usually combining lifestyle changes with medication.
高血壓危機
Systolic above 180 and/or diastolic above 120. In practice: if you have symptoms like chest pain, shortness of breath, or vision changes, this needs emergency care right away.
American Heart Association, 2025
Why Both Numbers Matter
More attention is often given to the systolic (top) number, since it’s a stronger predictor of heart disease risk for people over 50, as arteries naturally stiffen with age. But high diastolic pressure carries risk too, and a diagnosis is based on whichever number, systolic or diastolic, falls into the higher category.
A single reading also isn’t the full picture. Blood pressure naturally fluctuates through the day, so a diagnosis is usually based on the average of two or more readings taken on separate occasions, not one number in isolation.
Watch: Blood Pressure Explained
Two short explainers covering how blood pressure works and what the categories mean:
What Is Blood Pressure? — Khan Academy
A clear, visual walkthrough of what systolic and diastolic pressure actually measure during a heartbeat.
What the Updated Blood Pressure Guidelines Mean for You
A news explainer on how the current blood pressure categories were defined and what they mean for patients.
- American Heart Association. Understanding Blood Pressure Readings (2025).
- American Heart Association. Life’s Essential 8 — How to Manage Blood Pressure Fact Sheet.
- Whelton PK, et al. “2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults.” Hypertension (2018).
This page provides general health information and is not a substitute for personalized medical advice. Only a qualified healthcare professional can confirm a blood pressure diagnosis or recommend treatment based on your individual health history.
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Your care team can help you understand what this means for you specifically.
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