What Is Low Blood Pressure? (2024)

Low blood pressure (hypotension) is the opposite of high blood pressure (hypertension). Normal blood pressure readings are typically between 90/60 and 120/80 mmHg (millimeters of mercury). The top and bottom numbers of a blood pressure reading represent systolic and diastolic pressure. Having a top number below 90 or a bottom number under 60 is considered low blood pressure.

This article explains why some low blood pressure (LBP) readings below 90/60 mm Hg are considered "normal," what makes low blood pressure problematic for some, how to distinguish serious symptoms that are dangerous from those that aren't, when to seek emergency medical treatment, and more.

Low Blood Pressure Symptoms

• Dizziness
• Lightheadedness (presyncope)
  
• Fainting (syncope)
• Confusion
• Fatigue
• Generalized weakness
  
• Sudden blurry vision
• Headache
• Back and neck pain
• Nausea
• Palpitations
• Abnormal heart rhythm (arrhythmia)

Many people with chronic low blood pressure under 90/60 mm Hg are asymptomatic or experience mild, barely noticeable symptoms. That said, if you experience any of the above symptoms associated with low blood pressure, speak to a healthcare provider.

Dangerous Low Blood Pressure: What’s Considered Serious?

The biggest danger associated with severely low blood pressure is inadequate tissue perfusion, meaning that vital organs don't get enough blood flow and oxygen, called hypoperfusion. It can be deadly if low blood pressure causes insufficient blood flow, leading to hypoperfusion.Although extremely low blood pressure can be dangerous, hypotension doesn't always lead to organ hypoperfusion.

What Causes Blood Pressure to Drop?

Changes in body position, such as standing up quickly, commonly cause blood pressure to drop. This type of low blood pressure is called postural (orthostatic) hypotension. Orthostatic hypotension is the most common form of low blood pressure.Other things that may cause low blood pressure include:

• Dehydration
• Laying in bed for long periods
• Eating a big meal (postprandial hypotension)
• Pregnancy
• Problems with the autonomic nervous system
• Diabetes
• Parkinson's disease
• Abnormal heart rhythm
• Medications used to treat high blood pressure
  
• Blood loss from an injury (hemorrhage)
  

Sudden blood pressure drops caused by blood loss (hemorrhaging) or severe infection should always be treated as emergencies. When abnormally low blood pressure triggers acute circulatory failure, it causes shock, a serious life-threatening condition that requires immediate medical attention. Septic shock caused by an infection is also marked by dangerously low blood pressure.

Testing to Diagnose Low Blood Pressure

Routine blood pressure tests can diagnose low blood pressure, a blood pressure reading below 90/60 mm Hg. Blood tests, urine samples, and imaging are also used to diagnose low blood pressure. If someone with low blood pressure faints often, a tilt table test may be used during diagnosis.

In medical emergencies, healthcare providers often use mean arterial pressure or MAP to monitor and diagnose low blood pressure in critically ill patients. MAP readings above 65 are a target that usually means blood pressure isn't dangerously low. Notably, prolonged MAP readings below 65 for more than two hours can be dangerous and are associated with higher mortality rates.

Low Blood Pressure Treatment

People who technically have low blood pressure based on a "top number" reading below 90 or a "bottom number" below 60 but are asymptomatic (or have very mild symptoms) typically don't require treatment.

If someone with low blood pressure is experiencing notable symptoms, these treatments may help:

• Getting up more slowly
  
• Increasing salt intake
• Drinking more water
• Wearing compression stockings
• Not standing for long periods

Always talk to a healthcare provider before trying any of these treatments. In cases of severe low blood pressure, pharmaceuticals or other medical treatments may be prescribed.

How to Check Low Blood Pressure at Home

Home blood pressure monitoring(HBPM) is a readily accessible and affordable way to check low blood pressure at home. There are lots of easy-to-use HBPM products available for home use.

If you have severe low blood pressure symptoms, a healthcare provider may recommend anambulatory blood pressure monitoring (ABPM)device that records your blood pressure constantly over 24 hours. Unlike inaccurate"whitecoat" readingsthat often occur during stressful doctor visits, ABPM provides highly accurate blood pressure readings at home and as you go about daily life.

What to Do During a Sudden Drop in Blood Pressure

Sitting down is the best thing to do during a sudden drop in blood pressure. Sudden blood pressure drops can lead to fainting and falls; sitting helps avoid this. You can also try lying down and elevating your legs above the heart, which increases cardiac output and boosts blood pressure.

If a sudden drop in blood pressure causes someone to lose consciousness or go into shock, call 911 immediately.

Outlook

In general, the outlook for low blood pressure is good. Many people go about their day-to-day lives with chronically low blood pressure without experiencing any symptoms. Whereas high blood pressure is associated with poor outcomes, having low blood pressure isn't necessarily a bad thing. However, if low blood pressure does cause symptoms, it's important to speak with a healthcare provider right away and to seek medical attention immediately if a sudden drop in blood pressure triggers shock.

Summary

Low blood pressure is considered a reading below 90/60 mm Hg. Although having a top number below 90 or a bottom number below 60 is technically considered low blood pressure, many people have chronically low blood pressure without experiencing negative symptoms. If low blood pressure doesn't cause symptoms, it usually doesn't require treatment.