Low blood pressure, or hypotension, occurs when blood pressure during and after each heartbeat is much lower than usual. This means the heart, brain, and other parts of the body do not get enough blood.
Blood pressure that is borderline low for one person may be normal for another. Most normal blood pressures fall in the range of 90/60 millimeters of mercury (mm Hg) to 130/80 mm Hg. But a significant drop, even as little as 20 mm Hg, can cause problems for some people.
There are three main types of hypotension:
Orthostatic hypotension, including postprandial orthostatic hypotension
Neurally mediated hypotension (NMH)
Severe hypotension brought on by a sudden loss of blood (shock), infection, or severe allergic reaction
Orthostatic hypotension is brought on by a sudden change in body position, most often when shifting from lying down to standing. This type of hypotension usually lasts only a few seconds or minutes. If this type of hypotension occurs after eating, it is called postprandial orthostatic hypotension. This form most commonly affects older adults, those with high blood pressure, and persons with Parkinson's disease.
NMH most often affects young adults and children. It occurs when a person has been standing for a long time. Children usually outgrow this type of hypotension.
Low blood pressure is commonly caused by drugs such as:
Heart medicines, including those used to treat high blood pressure and coronary heart disease
The health care provider will examine you and try to determine what is causing the low blood pressure. Your vital signs (temperature, pulse, rate of breathing, blood pressure) will be checked frequently. You may need to stay in the hospital for a while.
The doctor will ask questions, including:
What is your normal blood pressure?
What medications do you take?
Have you been eating and drinking normally?
Have you had any recent illness, accident, or injury?
What other symptoms do you have?
Did you faint or become less alert?
Do you feel dizzy or light-headed when standing or sitting after lying down?
Hypotension in a healthy person that does not cause any problems usually doesn't require treatment.
If you have signs or symptoms of low blood pressure, you may need treatment. Treatment depends on the cause of your low blood pressure. Severe hypotension caused by shock is a medical emergency. You may be given blood through a needle (IV), medicines to increase blood pressure and improve heart strength, and other medicines, such as antibiotics. For more details, see the article on shock.
If you have orthostatic hypotension caused by medicines, your doctor may change the dose or switch you to a different drug. DO NOT stop taking any medicine before talking to your doctor. Other treatments for orthostatic hypotension include increasing fluids to treat dehydration or wearing elastic hose to boost blood pressure in the lower part of the body.
Those with NMH should avoid triggers, such as standing for a long period of time. Other treatments involve drinking plenty of fluids and increasing the amount of salt in your diet. (Ask your doctor about specific recommendations.) In severe cases, medicines such as fludrocortisone may be prescribed.
Low blood pressure can usually be treated with success.
Injury from falls due to fainting
Falls are particularly dangerous for older adults. Fall-related injuries, such as a broken hip, can dramatically impact a person's quality of life.
Severe hypotension starves your body of oxygen, which can damage the heart, brain, and other organs. This type of hypotension can be life threatening if not immediately treated.
Calling your health care provider
When you have symptoms from a drop in blood pressure, you should immediately sit or lie down and raise your feet above heart level.
If low blood pressure causes a person to pass out (become unconscious), seek immediate medical treatment or call the local emergency number (such as 911). If the person is not breathing or has no pulse, begin CPR.
Call your doctor immediately if you have any of the following symptoms:
If you have low blood pressure, your doctor may recommend certain steps to prevent or reduce your symptoms. This may include:
Avoiding standing for a long time (if you have NMH)
Drinking plenty of fluids
Getting up slowly after sitting or lying down
Using compression stockings to increase blood pressure in the legs
Calkins H, Zipes DP. Hypotension and syncope. In: Libby P, Bonow RO, Mann DL, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 37.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.