What is low blood pressure?
Low blood pressure means that your blood pressure is lower than normal. Another name for low blood pressure is hypotension (say "hy-poh-TEN-shun").
In most healthy adults, low blood pressure does not cause problems or symptoms. In fact, it may be normal for you. For example, people who exercise regularly often have lower blood pressure than people who are not as fit.
But if your blood pressure drops suddenly or causes symptoms like dizziness or fainting, it is too low. It can cause shock. Shock can be dangerous if it is not treated right away.
Blood pressure is a measure of how hard the blood pushes against the walls of your arteries as it moves through your body. Blood pressure consists of two numbers: systolic and diastolic.
- The systolic (higher) number shows how hard the blood pushes when the heart is pumping.
- The diastolic (lower) number shows how hard the blood pushes between heartbeats, when the heart is relaxed and filling with blood.
Someone with a systolic pressure of 120 and a diastolic pressure of 80 has a blood pressure of 120/80, or "120 over 80." Normal blood pressure is lower than 120/80.
Low blood pressure does not have a specific number where it is too low. Most doctors consider blood pressure to be too low when it causes symptoms or drops suddenly. In general, low blood pressure symptoms happen when blood pressure is less than 90/60.
What causes low blood pressure?
Some of the causes of low blood pressure include:
- Getting up after you sit or lie down. This can cause a quick drop in blood pressure called orthostatic hypotension.
- Standing for a long time.
- Not drinking enough fluids (dehydration).
- Medicines, such as high blood pressure medicine or other heart medicines.
- Health problems such as thyroid disease, severe infection, bleeding in the intestines, or heart problems.
- Trauma, such as major bleeding or severe burns.
What are the symptoms?
Many people with low blood pressure don't have any symptoms.
Symptoms to watch for include:
- Feeling dizzy, lightheaded, or faint.
- Feeling sick to your stomach or vomiting.
- Feeling more thirsty than usual.
- Having blurry vision.
- Feeling weak.
- Being confused.
- Being tired.
- Having cold, clammy skin.
- Breathing very fast.
If you have symptoms of low blood pressure, especially dizziness or fainting, call your doctor.
Watch for symptoms of low blood pressure. Tell your doctor when the symptoms happen so he or she can treat them.
How is low blood pressure diagnosed?
Often people learn that they have low blood pressure when their doctor checks it. Or you may find that you have low blood pressure when you check it at home.
To check for the causes of your low blood pressure, your doctor will ask about your past health, your symptoms, and the medicines you take. He or she will do a physical exam and may do other tests. Your doctor may check for another health problem that could be causing your low blood pressure.
Will your doctor treat low blood pressure?
You will likely get treated for low blood pressure only if it is causing symptoms or if your blood pressure drops suddenly. Treatment depends on your symptoms, how severe they are, and the reasons for the low blood pressure.
Your doctor may have you:
- Add more salt to your diet.
- Get fluid through an intravenous (IV) line if you are very dehydrated.
- Change or stop medicines that lower your blood pressure.
- Take medicine to treat the problem that is causing low blood pressure. For example, you may need antibiotics to treat infection or medicines to stop vomiting or diarrhea.
Be sure to talk with your doctor before you add more salt to your diet or make any changes in your medicines.
How can you prevent low blood pressure symptoms?
If you have orthostatic hypotension, your doctor may suggest that you try some simple ways to prevent symptoms like dizziness. For example, you can:
- Stand up slowly.
- Drink more water.
- Drink little or no alcohol.
- Limit or avoid caffeine.
- Wear compression stockings.
If you feel dizzy or lightheaded, sit down or lie down for a few minutes. Or you can sit down and put your head between your knees. This will help your blood pressure go back to normal and help your symptoms go away.
Other Works Consulted
- American Heart Association (2012). Low blood pressure. Available online: http://www.heart.org/HEARTORG/Conditions/HighBloodPressure/AboutHighBloodPressure/Low-Blood-Pressure_UCM_301785_Article.jsp.
- National Heart, Lung, and Blood Institute (2010). Hypotension. National Heart, Lung, and Blood Institute. http://www.nhlbi.nih.gov/health/health-topics/topics/hyp. Accessed March 21, 2016.
- Shen W-K, et al. (2017). 2017 ACC/AHA/HRS guideline for the evaluation and management of patients with syncope. Circulation, published online March 9, 2017. DOI: 10.1161/CIR.0000000000000499. Accessed March 30, 2017.
Current as of: December 16, 2019
Author: Healthwise Staff
Medical Review: E. Gregory Thompson, MD - Internal Medicine
Martin J. Gabica, MD - Family Medicine
Elizabeth T. Russo, MD - Internal Medicine
Adam Husney, MD - Family Medicine
Ethan A. Halm, MD, MPH - Internal Medicine