At a recent appointment, your doctor says, “You’ll be happy to hear your blood pressure is down from 140 over 90 to 120 over 80.”
“Great news!” you reply. But what do these fraction-like numbers actually mean?
Don’t worry. You won’t need advanced math skills to figure it out.
First, let’s get a better understanding of what blood pressure is. Picture your blood vessels and arteries as tubes. Blood is trying to go from one side of the tube to the other. As the blood moves, it’s pushing against the tube or vessel’s walls. That force is blood pressure.
How to Read Blood Pressure Numbers
Now let’s explore the measurement. Blood pressure is always shown as two numbers. Use 120 over 80, which is written as 120/80 mm Hg (millimeters of mercury), as an example. The “120” is the top number and is known as systolic blood pressure. It represents the pressure in your arteries when your heart beats. The “80” is the bottom number and is known as diastolic blood pressure. This is the pressure measured between your heartbeats when your heart is relaxing.
While both numbers are important, the American Heart Association notes the top number usually gets more attention. That’s because it helps show your risk of having a stroke or heart attack, along with kidney disease, congestive heart failure, vision loss and memory loss.
A high systolic reading is considered a major heart disease risk factor for people older than 50. As we age, arteries can become stiff and develop plaque buildup. In other words, if your blood is essentially punching the walls inside your heart, over and over again, damage will eventually occur.
Here’s how the American Heart Association categorizes blood pressure levels.
- Normal: systolic less than 120 and diastolic less than 80
- Prehypertension: systolic 120-139 or diastolic 80-89
- Stage 1 high blood pressure: systolic 140-159 or diastolic 90-99
- Stage 2 high blood pressure: systolic 160 or higher or diastolic 100 or higher
- Hypertensive crisis (seek emergency care): systolic higher than 180 or diastolic higher than 110
Low blood pressure is typically not a problem unless you notice symptoms like:
- Dizziness
- Fainting
- Lack of concentration
- Blurred vision
- Nausea
- Clammy skin
- Shallow breathing
- Fatigue
- Depression
How Often You Should Check Your Blood Pressure
The American Heart Association recommends checking your blood pressure beginning at age 20 and measuring it every two years if it’s normal. If it’s high, your doctor will want to see you more often, especially if you are controlling it with medication. A primary care doctor can check your blood pressure and take steps to help you keep it well controlled. Talk to your doctor if you have concerns about your blood pressure.
Remember: Even extremely high blood pressure levels may not cause noticeable symptoms. Get to the emergency department or call 911 if you have weakness on one side, slurred speech, severe headaches, or vision changes such as blind spots or blurred vision.