Blood pressure reading

What it means

The top number, systolic pressure, is the force when the heart pumps. The bottom number, diastolic pressure, is measured between beats. A reading of 120/80 mm Hg is said "120 over 80."

US categories for adults:

• Normal: below 120 and below 80
• Elevated: 120 to 129 and below 80
• Stage 1 high blood pressure: 130 to 139 or 80 to 89
• Stage 2 high blood pressure: 140 or higher or 90 or higher

A reading above 180 and/or above 120 needs prompt care. With symptoms such as chest pain, shortness of breath, weakness or trouble speaking, call 911.

One reading is a snapshot. Sit quietly for a few minutes first, keep feet flat and your arm supported at heart level, and use a cuff that fits. Home readings taken the same way over days give a clearer picture than a single office check.

Why it matters

Blood pressure often improves with weight loss, so tracking it shows a health benefit the scale cannot.