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What Those Blood Pressure Numbers Mean

A quick, painless test measures blood pressure. A rubber cuff is wrapped around your arm and inflated. The cuff compresses an artery in your arm and momentarily stops your blood flow. A doctor, nurse, or technician uses a stethoscope to measure your blood pressure when the pressure in the cuff is released.

If your blood pressure reading is high during a doctor visit, your doctor will take another reading after waiting several minutes, or even on another visit. If it is still high after two or more readings, your doctor will probably make the diagnosis of high blood pressure, or hypertension.

If you are going to check your blood pressure at home, talk to your doctor about the type of blood pressure monitor you need. Electronic monitors may be convenient, but they may not be as accurate as a manual blood pressure cuff, especially in people with heart rhythm problems.

If you are using a monitor to check your blood pressure at home, here are some tips from the American Heart Association (AHA) to help you take an accurate blood pressure:

• Make sure the blood pressure cuff fits: measure around your upper arm and choose a monitor that comes with the correct size cuff.
• Don't smoke,drink caffeine or exercise within half an hour before measuring your blood pressure.
• Sit with your back straight and supported (on a hard chair, for example, rather than a sofa) with your feet flat on the floor. Your arm should be supported on a flat surface (such as a table) with the upper part of the arm at heart level. Make sure the middle of the cuff is placed directly over your brachial artery -- check your monitor's instructions for an illustration or have your healthcare provider show you how.
• Each time you measure, take two or three readings, at least one minute apart, and record all the results.
• It's important to take the readings at the same time each day, such as morning and evening, or as your healthcare professional recommends.

By the numbers

Blood-pressure readings are recorded as two numbers. Both are a measurement of the force of the blood against arterial walls. The first, higher number is the systolic pressure, which indicates the pressure of the blood against the arteries when the heart contracts to pump blood. The second, lower number is the diastolic pressure, which indicates the pressure of the blood against the artery walls when the heart is resting in between beats. It indicates the elasticity of the arteries. When blood pressure is recorded, the systolic pressure is always recorded first, followed by a diagonal line and the diastolic pressure.

The higher the number, the harder it is for the heart to pump blood. In a person who has not been diagnosed with high blood pressure or who does not have a chronic illness, a systolic reading above 140 or a diastolic reading above 90 indicates hypertension or high blood pressure.

Here are the numbers to look for when you or someone else is checking your blood pressure, according to the National Heart, Lung, and Blood Institute.

Your systolic and diastolic numbers may not be in the same blood pressure category. In this case, the more severe category is the one you're in.

The ranges in the table above apply to most adults who don't have other serious diseases. If you have diabetes or chronic kidney disease, high blood pressure is defined as 130/80 or higher, according to the NHLBI.

All levels above 120/80 raise your risk of related problems such as heart attack and stroke, and the risk grows as blood pressure levels rise. "Prehypertension" means you're likely to end up with high blood pressure, unless you take steps to prevent it.

It's important to know if you have high blood pressure so you can take steps to control it and reduce your risk for related health problems. Key steps include following a healthy lifestyle, continuing to be monitored, and following the treatment plan your doctor recommends.