Understanding blood pressure (also known as hypertension) isn’t easy, especially when words like “systolic,” “diastolic,” and “millimeters of mercury” (mm Hg) are involved. In order to keep high blood pressure under control, it’s important to know what levels are considered normal, as well as how to tell when your blood pressure is too high.
By learning some basic concepts, you can become an expert in reading and understanding your blood pressure numbers. Read on to have hypertension explained to you.
Everyone would like to have healthy, normal blood pressure. But what exactly does that mean? When your doctor takes your blood pressure, it’s expressed as a measurement with two numbers, with one number on top and one on the bottom, like a fraction.
The top number refers to the amount of pressure in your arteries during contraction of your heart muscle; this is called “systolic” pressure. The bottom number refers to your blood pressure when your heart muscle is between beats; this is called “diastolic” pressure.
For a normal reading, your blood pressure needs to show a top number that’s lower than 120, and a bottom number that’s lower than 80.
When both your systolic and diastolic numbers are in these ranges, then you are considered by the American Heart Association (AHA) to be within the normal range for blood pressure.
Note that blood pressure readings are expressed as “millimeters of mercury,” which is abbreviated as “mm Hg.” So a normal reading would be any blood pressure below 120/80 mm Hg.
Numbers higher than 120/80 are a red flag that you need to take on heart-healthy habits.
When your systolic (upper number) is between 120 and 139 mm Hg or your diastolic (lower number) is between 80 and 89, it means you have “prehypertension.”
Although these numbers aren’t technically considered “high blood pressure,” you’ve moved out of the normal range. Elevated blood pressure has a good chance of turning into actual high blood pressure, which puts you at increased risk of heart disease and stroke.
You’ll generally be diagnosed with high blood
pressure if your systolic blood pressure reaches between 140 and 159 mm Hg, or if your diastolic blood pressure
reaches between 90 and 99 mm Hg. This is considered “stage 1” hypertension.
However, the AHA notes that if you get only one reading this high, you may not truly have high blood pressure. What determines the diagnosis of hypertension at any stage is if your numbers remain this high over a period of time.
Your doctor can help you measure and track your blood pressure to confirm whether it is too high.
If stage 1 high blood pressure is cause for concern, stage 2 high blood pressure indicates an even more serious condition. If your blood pressure reading shows a top number of 160 or more, or a bottom number of 100 or more, this is considered stage 2 hypertension.
At this stage, in addition to making lifestyle changes—such as losing weight, eating better, and exercising more—your doctor may recommend one or more medications for keeping your blood pressure under control.
A blood pressure reading above 180/110 mm Hg—or having either the systolic or diastolic numbers higher than this—indicates a serious health problem.
The AHA refers to these high measurements as a “hypertensive crisis.” Blood pressure in this range generally requires emergency treatment.
However, sometimes one high reading can occur, and then your numbers will return to normal. If your blood pressure measures at this level, your doctor will likely take a second reading after a few minutes have passed. A second high reading indicates that you’ll need emergency medical services.
blood pressure is not cause for complacency. The AHA recommends that even people with healthy
numbers take preventive measures to help keep their blood pressure in the
normal range, and also avoid the chance of developing hypertension or heart
As you age, prevention becomes even more important. Systolic pressure tends to creep up once you’re over 50, according to the AHA. Work on maintaining a healthy weight, which you can achieve through diet and exercise. Having a healthy weight reduces your chances of high blood pressure.