Every reading has two numbers measured in millimetres of mercury (mmHg). The top, larger number is systolic pressure, the force in your arteries each time the heart contracts. The bottom, smaller number is diastolic pressure, the force when the heart is resting and refilling between beats.
Both numbers matter. A high systolic reading is a strong predictor of heart and stroke risk, especially in people over 50, while a raised diastolic is more important in younger adults. Doctors look at both alongside your age, other conditions, and overall risk.
If you are unsure how to interpret your own readings, a pharmacist or doctor can review your log and explain what your numbers mean for you. Do not change or stop any prescribed medicine based on a home reading without medical advice.