Blood Pressure Numbers: When to Get Help
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, footnote 2
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 lightheaded, 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.
- Whelton PK, et al. (2017). Guideline for the prevention, detection, evaluation, and management of high blood pressure in adults: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Journal of the American College of Cardiology, published online November 13, 2017. DOI: 10.1016/j.jacc.2017.11.006. Accessed November 20, 2017.
- Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (2003). Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure JNC Express (NIH Publication No. 03–5233). Bethesda, MD: U.S. Department of Health and Human Services.
Current as of: July 11, 2023
Author: Healthwise Staff
Clinical Review Board: All Healthwise education is reviewed by a team that includes physicians, nurses, advanced practitioners, registered dieticians, and other healthcare professionals.
Current as of: July 11, 2023