Low blood pressure (hypotension): symptoms and causes

Medical disclaimer: This page is general health information for education only. It is not medical advice and is not a substitute for diagnosis or treatment by a qualified health professional. It has not been reviewed by a clinician. In an emergency, call 911 or your local emergency number.

Low blood pressure, also called hypotension, means your blood moves through your blood vessels at lower than normal pressure. This page explains the reading used to define low blood pressure, its symptoms, its main types and causes, and when it is an emergency. It is part of our library of health conditions.

What is low blood pressure?

Low blood pressure is a reading lower than 90/60 mm Hg, according to the National Heart, Lung, and Blood Institute (NHLBI).

Blood pressure is the force of blood pushing against your artery walls as your heart pumps. It is measured in millimeters of mercury (mm Hg).

• For most adults, a normal blood pressure is usually less than 120/80 mm Hg.
• The NHLBI defines low blood pressure as lower than 90/60 mm Hg.
• Some people have low blood pressure all the time, and it is normal for them.
• Blood pressure varies from one person to another and over time in the same person.

There is no single cutoff that fits everyone. MedlinePlus notes that a drop of as little as 20 mm Hg can cause problems for some people, even when the reading is not below 90/60. This page gives general information for adults. It does not cover low blood pressure in children or during pregnancy. If you want to understand high readings instead, see our guide to high blood pressure numbers and categories.

What are the symptoms of low blood pressure?

Common symptoms of low blood pressure include dizziness, lightheadedness, fainting, blurry vision and feeling tired or weak.

For many people, low blood pressure goes unnoticed and causes no symptoms at all.

The NHLBI lists these symptoms of low blood pressure:

• Confusion
• Dizziness or lightheadedness
• Fainting
• Feeling tired or weak
• Blurry vision
• Headache
• Neck or back pain
• Nausea
• Heart palpitations, which feel like your heart is skipping, fluttering, or beating too hard or too fast

Older adults have a higher risk of falling, fainting or dizziness on standing up or after a meal. MedlinePlus also lists nausea or vomiting and sleepiness. Falls from low blood pressure in older adults can lead to a broken hip or spine fracture.

These symptoms are not specific to low blood pressure. Dizziness, confusion and fainting have many other causes that this page does not help you rule out.

What are the types of low blood pressure?

The main types of low blood pressure are orthostatic, postprandial, neurally mediated and severe hypotension, which is linked to shock.

• Orthostatic hypotension is also called postural hypotension.
• Orthostatic hypotension is a drop of at least 20 mm Hg systolic or 10 mm Hg diastolic within 3 minutes of standing.
• Orthostatic hypotension affects about 6 percent of the population.
• Orthostatic hypotension affects at least 10 to 30 percent of older adults.
• Most people with orthostatic hypotension have no symptoms from it.
• Children usually outgrow neurally mediated hypotension.

Sources: MedlinePlus Genetics on orthostatic hypotension and the MedlinePlus Medical Encyclopedia. Only a clinician can tell which type, if any, applies to you. A short dizzy spell on standing does not by itself mean you have orthostatic hypotension.

What causes low blood pressure?

Low blood pressure can come from dehydration, blood loss, some medicines, heart problems, nerve problems and hormone conditions.

The NHLBI names these causes:

• Problems with the autonomic nervous system, such as in Parkinson disease. The autonomic nervous system controls organs that work without your thinking, such as the heart and blood vessels.
• Blood loss from an injury
• Dehydration
• Diabetes
• Heart problems such as arrhythmias (irregular heartbeat)
• Medicines to treat high blood pressure, depression or Parkinson disease
• Pregnancy

The American Heart Association adds other groups of causes:

• Heart problems: an abnormally low heart rate (bradycardia), heart valve problems, heart attack and heart failure. Our overview of heart disease explains common heart conditions and heart attack warning signs.
• Endocrine (hormone) problems: underactive thyroid, Addison’s disease, low blood sugar and diabetes.
• Nutrition: a lack of vitamin B-12 or folic acid, which can cause anemia (too few red blood cells).
• Other situations: prolonged bed rest or prolonged standing.

MedlinePlus lists medicine classes that can lower blood pressure, including diuretics, heart medicines, certain antidepressants, anti-anxiety medicines, painkillers and medicines used for surgery. Alcohol can also lower it. Older adults are more likely to develop low blood pressure as a side effect of medicines for high blood pressure.

These lists are not complete, and a cause on the list may not be the cause for you. Do not stop taking any medicine before talking to your clinician, as MedlinePlus advises.

In short, low blood pressure matters when it causes symptoms, drops suddenly or signals another condition. The reading, your symptoms and the likely cause together decide whether it needs attention.

When is low blood pressure an emergency?

Low blood pressure is an emergency when it causes signs of shock or makes someone pass out. Call 911 right away.

Shock is a state in which not enough blood flows through the body, which damages cells and tissues. The NHLBI lists these signs of shock:

• Cold and sweaty skin
• Rapid breathing
• A blue skin tone
• A weak and rapid pulse

Call 911 if you notice signs of shock in yourself or someone else. If low blood pressure makes a person pass out, seek treatment right away or call 911. If the person is not breathing or has no pulse, begin CPR, as MedlinePlus advises. Our first aid basics page explains what to do while you wait for help.

Call your clinician right away if you have black or maroon stools, chest pain, dizziness, fainting, a fever higher than 101°F (38.3°C), an irregular heartbeat or shortness of breath. This page does not replace emergency care. When in doubt, call 911.

How do clinicians evaluate low blood pressure?

Clinicians diagnose low blood pressure with a blood pressure test, then look for the cause with questions, an exam and other tests.

The NHLBI says other tests may include blood, urine or imaging tests. A tilt table test may be used if you faint often. During a tilt table test, you lie on a table that is slowly tilted upward. The test measures how your blood pressure and heart rate respond to gravity.

According to MedlinePlus, your clinician may ask:

• What is your normal blood pressure?
• What medicines do you take?
• Have you been eating and drinking normally?
• Have you had any recent illness, accident or injury?
• Do you feel dizzy or lightheaded when standing or sitting after lying down?

Tests may include blood work, a urine test, an electrocardiogram (ECG) and chest or abdominal X-rays. Lower than normal blood pressure in a healthy person without symptoms often does not need treatment. Otherwise, care depends on the cause and your symptoms. This page does not give treatment advice for your situation.

Questions to bring to your appointment

A short list of questions helps you use your visit well. Our guide on how to prepare for an appointment has more tips.

• Is my blood pressure low for me, or is it my normal?
• Could any of my medicines be lowering my blood pressure?
• Should my blood pressure be checked lying down and standing?
• Do my symptoms point to a type of low blood pressure, such as orthostatic hypotension?
• Which symptoms mean I should call you, and which mean I should call 911?
• Do I need any tests to look for a cause?

These questions are a starting point. They do not replace advice from a clinician who knows your health history.