2. What do the numbers mean?

When measuring blood pressure, the machine or doctor will report two numbers. The top number is systolic blood pressure -- it represents the pressure in the blood vessels when the heart beats. The bottom number is diastolic blood pressure, the pressure in between beats when the heart is resting. The mm Hg measurement stands for millimeters of mercury. The first accurate pressure gauges used mercury, but the unit of measure remained even when mercury fell out of use.

what is normal blood pressure

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