Blood pressure
Blood pressure is the force of blood inside an artery. A blood pressure reading measures the force of blood against the walls of an artery.
Blood pressure is measured by temporarily stopping the flow of blood in an artery, using a cuff placed around the upper arm. Air is added to the cuff until blood flow stops. As the air is released, blood begins to flow through the artery again. Blood pressure is measured as the blood begins to flow again.
- Blood pressure readings consist of an upper and lower number (such as 120 over 90 or 120/90). Blood pressure readings are measured in units called millimeters of mercury (mm Hg).
- Systolic blood pressure is the first or upper number in a blood pressure reading. Systolic pressure is the pressure of blood against the artery walls when the heart has just finished contracting or pumping.
- Diastolic blood pressure is the second or lower number in a blood pressure reading. Diastolic pressure is the pressure of blood against the artery walls between heartbeats, when the heart is relaxed and filling with blood.
What do your blood pressure numbers mean?
Blood pressure is a measure of the force of blood against the walls of your arteries. Blood pressure readings include two numbers. The first number is the systolic pressure (top number). This is the force of blood on the artery walls as your heart pumps. The second number is the diastolic pressure (bottom number). This is the force of blood on the artery walls between heartbeats.
It's normal for blood pressure to go up and down throughout the day. But if the top number stays high, or the bottom number stays high, or both, that means you have high blood pressure (hypertension). For diagnosis, the top number may be 130 to 140 or higher. The bottom number may be 80 to 90 or higher.
Your doctor will give you a goal for your blood pressure. Your goal will be based on your health and your age.
What can cause blood pressure to go up or down?
It's normal for blood pressure to go up and down throughout the day. Things like exercise, stress, and sleeping can affect your blood pressure. Some medicines can cause your blood pressure to go up. These medicines include certain asthma medicines and cold remedies.
A low blood pressure reading can be caused by many things, including some medicines, a severe allergic reaction, or an infection. Another cause is dehydration, which is when your body loses too much fluid.
©2011-2024 Healthwise, Incorporated