A blood pressure reading takes less than a minute, but doctors get far more out of it than most people realize. The two numbers on the screen are only the starting point.
Every reading is shaped by how hard your heart is pumping, how flexible your arteries are and how well your body adjusts when you change position. A trained eye can pick up on small details in those numbers that show how your heart and blood vessels are holding up over time.
Here are 5 things doctors look for during a blood pressure reading, and what each one tells them about what’s happening inside your body.
1. Both Numbers and Where They Fall
A reading has two numbers. The top number, called systolic pressure, measures the force of blood pushing against your artery walls when your heart beats. The bottom number, called diastolic pressure, measures that force while your heart rests between beats. According to the American Heart Association, a reading under 120/80 is considered normal, a top number of 120 to 129 with a bottom number under 80 is elevated, and a top number of 130 or higher or a bottom number of 80 or higher falls into the high blood pressure range. Doctors look at both numbers, because either one can move a reading into a different range. [1]
2. The Gap Between the Two Numbers
Doctors also look at the space between the top and bottom numbers, called pulse pressure. According to Mayo Clinic, a reading of 120/80 has a pulse pressure of 40, which is considered healthy. The gap tends to widen as the body’s largest arteries stiffen, because a stiff artery can’t stretch to absorb each heartbeat, so the top number climbs while the bottom number stays the same or falls. Mayo Clinic notes that a pulse pressure greater than 60 is a concern, especially in older adults, and that a larger gap is linked to stiffer, more strained blood vessels. [2]
3. A Difference Between Arms
Your two arms don’t always give the same number. Harvard Health Publishing reports that in one study, the top number differed by more than 10 points between arms in 15% of patients, and the arm with the higher reading often switched from one visit to the next. Because of this, the American Heart Association advises checking both arms at the first visit, then using the arm with the higher reading going forward. [3]
4. Your Heart Rate
Most blood pressure monitors also show your pulse, and doctors read the two together. According to the American Heart Association, blood pressure is the force of blood moving through your vessels, while heart rate is the number of times your heart beats per minute. A normal resting heart rate falls between 60 and 100 beats per minute. Reading the two side by side shows both how hard and how often your heart is working to move blood through your body. [4]
5. How Your Numbers Change When You Stand
Some doctors check blood pressure while you’re sitting and again after you stand up. When you stand, gravity pulls blood toward your legs, and your blood vessels have to tighten quickly to keep blood flowing to your brain. According to Mayo Clinic, a drop of 20 points in the top number or 10 points in the bottom number within 2 to 5 minutes of standing is considered significant. This shows doctors how well your body adjusts to a change in position, something a seated reading on its own can’t reveal. [5]
What a Reading Really Shows
A blood pressure reading captures several things happening at once: the force of each heartbeat, the flexibility of your arteries, the pace of your heart and how quickly your body responds when you move.
Two people can walk away with the same numbers and be in very different places. The gap between the numbers, the difference between arms, your pulse and how your reading changes when you stand all add detail that a single number can’t. Together, they give a far more complete picture of how your heart and blood vessels are holding up as the years go by.
