To take a blood pressure measurement, your health professional will usually follow these steps:

• You will be asked to sit down with your arm supported at heart level.
• A cuff made of a rubber sac that fills with air will be wrapped around your upper arm.
• Your health professional will seal the cuff and pump it up until you feel pressure around your arm.
• First, your systolic blood pressure—the pressure when your heart contracts—will be taken. The cuff will be tightened to a pressure higher than your systolic blood pressure value. At this point, your pulse cannot be heard through a stethoscope. Next, the pressure from the cuff will be reduced. When the cuff pressure drops to the same level as your systolic blood pressure, the health professional will be able to hear your pulse. This will allow a reading of your systolic blood pressure.
• Next, your diastolic blood pressure—the pressure when your heart relaxes—will be taken. The health professional will continue to release the pressure from the cuff after taking your systolic blood pressure. Your pulse will remain audible until the pressure in the cuff is the same as your diastolic blood pressure. This allows a reading of your diastolic blood pressure.

Although blood pressure measurements taken at your doctor's office may be more precise than other types of measurements, even a professional reading of your blood pressure may change from time to time. Your blood pressure changes for many reasons, including exercise, stress, relaxation, time of day, alcohol intake, caffeine, or medicines.