Blood pressure is exactly what it sounds like. When blood is pumped out of your heart, it exerts a force on the walls of your arteries. This force, along with the resistance your arteries exert as the blood passes through them, is what makes up your blood pressure.
When we're healthy, our arteries are muscular and elastic, and stretch to allow blood to pass through them more easily. Your blood pressure can fluctuate throughout the day, depending on your posture, level of activity, wakefulness, and stress.
Why two numbers?
Blood pressure is measured in two numbers, one "over" the other. The first number records your blood pressure at its highest, or when your heart beats. This number is referred to as systolic pressure. The second or bottom number is a measurement of your blood pressure at its lowest when your heart is at rest between beats. This number is called the diastolic pressure. Blood pressure is therefore read as systolic pressure over diastolic pressure, and is measured in millimeters of mercury, or mm Hg.
How often should I have my blood pressure checked?
While it's okay to check your own blood pressure using one of the blood pressure reading machines at the pharmacy or gym, it's important to have it regularly checked by a healthcare professional. If you know your blood pressure is normal, you should have it checked by a doctor or nurse (at least) every two years — more if you have, or are at risk for, high blood pressure.
How do they check blood pressure?
To measure your blood pressure, your doctor or more likely a nurse or other healthcare professional will place a rubber cuff around your upper arm. He or she will then pump air into the cuff. When the cuff is fully inflated, it will compress a large artery in your arm to momentarily stop the blood flow. The person taking your blood pressure will then slowly release air from the cuff and listen with a stethoscope placed on the compressed artery. When your blood begins to flow again, it will make a sound audible through the stethoscope. The sound will continue until the pressure in your artery exceeds the pressure in the cuff. The nurse will check a gauge and note when he or she first hears the noise (this is the systolic reading) and when the noise stops (this is the diastolic reading).
What is a healthy blood pressure?
According to the American Heart Association, a healthy blood pressure is less than 120/80 mm Hg. However, some physicians consider the ideal reading to be 115/75 mm Hg. High blood pressure, called hypertension, occurs when blood pressure is greater than 140/90 mm Hg. A reading between 120/80 and 140/90 indicates prehypertension, which means you are at significant risk for developing high blood pressure.
< 120/80 mm Hg Normal
120/80 to 139/89 mm Hg Prehypertension
140/90 to 159/99 mm Hg Stage 1 hypertension
> 160/100 mm Hg Stage 2 hypertension
