Low blood pressure
Definition
Low blood pressure occurs when blood pressure is much lower than normal. This means the heart, brain, and other parts of the body may not get enough blood. Normal blood pressure is mostly between 90/60 mmHg and 120/80 mmHg.
The medical word for low blood pressure is hypotension.
Alternative Names
Hypotension; Blood pressure - low; Postprandial hypotension; Orthostatic hypotension; Neurally mediated hypotension; NMH
Causes
Blood pressure varies from one person to another. A drop of as little as 20 mmHg can cause problems for some people. There are different types and causes of low blood pressure.
Severe hypotension (shock) can be caused by sudden loss of blood (shock), severe infection, heart attack, or severe allergic reaction (anaphylaxis).
Orthostatic hypotension means your blood pressure drops when you shift from lying down to standing. This type of low blood pressure usually lasts only a few seconds or minutes. If this type of low blood pressure occurs after eating, it is called postprandial orthostatic hypotension. This type most often affects older adults, those with high blood pressure, and people with Parkinson disease.
Neurally mediated hypotension (NMH) most often affects young adults and children. It can occur when a person has been standing for a long time. Children usually outgrow this type of hypotension.
Certain medicines and substances can lead to low blood pressure, including:
- Alcohol
- Anti-anxiety medicines
- Certain antidepressants
- Diuretics
- Heart medicines, including those used to treat high blood pressure and coronary heart disease
- Medicines used for surgery
- Painkillers
Other causes of low blood pressure include:
- Nerve damage from diabetes or other disorders
- Changes in heart rhythm (arrhythmias)
- Not drinking enough fluids (dehydration)
- Heart failure
Symptoms
Symptoms of low blood pressure may include:
- Blurry vision
- Confusion
- Dizziness
- Fainting (syncope)
- Lightheadedness
- Nausea or vomiting
- Sleepiness
- Weakness
Exams and Tests
The health care provider will examine you to determine the cause of your low blood pressure. Your vital signs (temperature, pulse, rate of breathing, and blood pressure) will be checked frequently. You may need to stay in the hospital for a while.
The provider will ask questions, including:
- 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?
- What other symptoms do you have?
- Did you faint or become less alert?
- Do you feel dizzy or lightheaded when standing or sitting after lying down?
The following tests may be done:
- Basic metabolic panel
- Blood cultures to check for infection
- Complete blood count (CBC), including white blood cell differential
- Electrocardiogram (ECG)
- Urinalysis
- X-ray of the abdomen
- X-ray of the chest
Treatment
Lower than normal blood pressure in a healthy person that does not cause any symptoms often does not need treatment. Otherwise, treatment depends on the cause of your low blood pressure and your symptoms.
When you have symptoms from low blood pressure, sit or lie down right away. Then raise your feet above heart level.
Severe hypotension caused by shock is a medical emergency. You may be given:
- Blood or other fluids through a needle (IV)
- Medicines to increase blood pressure and improve heart strength
- Other medicines, such as antibiotics
Treatments for low blood pressure after standing up too quickly include:
- If medicines are the cause, your provider may change the dosage or switch you to a different medicine. Do not stop taking any medicines before talking to your provider.
- Your provider may suggest drinking more fluids to treat dehydration.
- Wearing compression stockings can help keep blood from collecting in the legs. This keeps more blood in the upper body.
People with NMH should avoid triggers, such as standing for a long period of time. Other treatments include drinking fluids and increasing salt in your diet. Talk to your provider before trying these measures. In severe cases, medicines may be prescribed.
Outlook (Prognosis)
Low blood pressure can usually be treated with success.
Possible Complications
Falls due to low blood pressure in older adults can lead to a broken hip or spine fracture. These injuries can reduce a person's health and ability to move about.
Sudden severe drops in your blood pressure starves your body of oxygen. This can lead to damage of the heart, brain, and other organs. This type of low blood pressure can be life threatening if not treated right away.
When to Contact a Medical Professional
If low blood pressure causes a person to pass out (become unconscious), seek treatment right away. Or call 911 or the local emergency number. If the person is not breathing or has no pulse, begin CPR.
Call your provider right away if you have any of the following symptoms:
- Black or maroon stools
- Chest pain
- Dizziness, lightheadedness
- Fainting
- Fever higher than 101°F (38.3°C)
- Irregular heartbeat
- Shortness of breath
Prevention
Your provider may recommend certain steps to prevent or reduce your symptoms including:
- Drinking more fluids
- Getting up slowly after sitting or lying down
- Not drinking alcohol
- Not standing for a long time (if you have NMH)
- Using compression stockings so blood does not collect in the legs
References
Calkins H, Everett TH, Chen P-S. Hypotension and syncope. In: Libby P, Bonow RO, Mann DL, Tomaselli GF, Bhatt DL, Solomon SD, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 12th ed. Philadelphia, PA: Elsevier; 2022:chap 71.
Schrigern DL. Approach to the patient with abnormal vital signs. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 7.
Reviewed By: Linda J. Vorvick, MD, Clinical Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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