Hypotension (Low Blood Pressure)

Overview

Hypotension means blood pressure that is lower than normal. Blood pressure is the force of blood against the artery walls, and a reading is generally considered low when it falls below about 90/60 mmHg, though the exact number matters less than whether it causes symptoms. For many people, naturally low blood pressure causes no problems at all and can even be a sign of good cardiovascular health.

Hypotension becomes a concern when blood pressure drops too low or too quickly to deliver enough blood to the brain and other organs. This can cause dizziness, lightheadedness, fainting, blurred vision, and fatigue. A common pattern is feeling dizzy when standing up quickly. A sudden, severe fall in blood pressure can be dangerous and is a medical emergency, especially when caused by major bleeding, infection, or a severe allergic reaction.

Common Causes

Blood pressure can fall for many reasons, from everyday triggers to serious illness. Common causes include:

• Standing up quickly: a brief drop on standing, called orthostatic hypotension.
• Dehydration: low fluid volume reducing blood pressure. See dehydration.
• Medications: blood pressure drugs, diuretics, and some heart and mental health medicines.
• Heart problems: a slow heart rate, valve problems, or weak pumping.
• Blood loss: bleeding reducing circulating volume. See hypovolemic shock.
• Serious causes: severe infection (sepsis) or a severe allergic reaction (anaphylaxis), which can cause shock.

Associated Symptoms

Hypotension may cause no symptoms or, when blood flow drops, lead to:

• Dizziness or lightheadedness, especially on standing
• Fainting or near-fainting
• Blurred vision
• Fatigue or weakness
• Nausea or difficulty concentrating
• Cold, clammy, pale skin and a rapid pulse when severe

Confusion, fainting, cold clammy skin, or a rapid weak pulse with low blood pressure can signal shock and need emergency care.

Diagnosis & Evaluation

A clinician evaluates hypotension by measuring blood pressure and looking for a cause. Evaluation may include:

• Blood pressure readings: taken lying down and standing to check for a drop on standing.
• History: symptoms, medications, fluid intake, and any bleeding or illness.
• ECG: to check the heart rhythm and rate.
• Blood tests: for anemia, infection, blood sugar, and hormone or electrolyte problems.
• Further tests: tilt-table testing or heart studies for recurrent fainting.

Treatment & Management

Hypotension without symptoms often needs no treatment. When it causes problems, care targets the cause:

• Hydration: drinking enough fluids, and sometimes increasing salt with medical advice.
• Slow position changes: rising gradually from lying or sitting to prevent dizziness.
• Reviewing medications: adjusting drugs that lower blood pressure, under medical guidance.
• Compression stockings: to reduce blood pooling in the legs for some people.
• Treating the cause: managing heart problems, infection, or hormone disorders.
• Emergency treatment: urgent fluids, medications, and addressing bleeding, infection, or allergy for a severe drop.

Many people with mild low blood pressure feel better simply by staying hydrated and changing position slowly. When low blood pressure is caused by an underlying condition, treating that condition is the key to lasting relief, so it is worth identifying the cause rather than only managing the dizziness.

Self-Care & Prevention

If you are prone to low blood pressure symptoms, several habits can help:

• Drink enough fluids, especially in hot weather or during exercise and illness.
• Stand up slowly from lying or sitting, and sit on the edge of the bed for a moment before rising.
• Eat smaller, more frequent meals if large meals make you feel faint afterward.
• Discuss with your doctor whether to adjust the timing of medications that lower blood pressure.
• Consider compression stockings if recommended, to reduce blood pooling in the legs.
• With medical advice, increasing salt and fluids can help some people.

Avoid prolonged standing in hot conditions and alcohol, which can lower blood pressure further. Report frequent dizziness or fainting to your doctor so the cause can be addressed.

When to See a Doctor

See a doctor if low blood pressure causes repeated dizziness, fainting, or fatigue, or if you notice it after starting a new medication. Call emergency services right away if low blood pressure comes with:

• Fainting or near-collapse
• Confusion or reduced alertness
• Cold, clammy, pale skin and a rapid, weak pulse
• Signs of heavy bleeding, severe infection, or a severe allergic reaction

A sudden severe drop in blood pressure with these signs can indicate shock and is a medical emergency.

Related Topics

Frequently Asked Questions

References

1. National Heart, Lung, and Blood Institute (NHLBI). Low Blood Pressure.
2. Mayo Clinic. Low blood pressure (hypotension) — Symptoms and causes.
3. MedlinePlus, U.S. National Library of Medicine. Low blood pressure.
4. American Heart Association. Low Blood Pressure.