Overview

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.^{footnote 1}

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.

When should you call your doctor?

One high or low blood pressure reading by itself may not mean you need to call for help. If you take your blood pressure and it is out of the normal range, wait a few minutes and take it again. If it's still high or low, use the following guidance.

Call 911 anytime you think you may need emergency care. For example, call if:

• You passed out (lost consciousness).

Call your doctor now or seek immediate medical care if:

• Your blood pressure is much higher than normal (such as 180/120 or higher).
• You think high blood pressure is causing symptoms such as:
  • Severe headache.
  • Blurry vision.
• You are dizzy or light-headed, or you feel like you may faint.

Watch closely for changes in your health, and be sure to contact your doctor if:

• Your blood pressure measures higher than your doctor recommends at least 2 times. That means the top number is higher or the bottom number is higher, or both.
• You think you may be having side effects from your blood pressure medicine.