Studies show a link between low blood pressure and an increased risk of stroke and an elevated risk of dying from stroke. However, scientists are not yet sure why low blood pressure raises the risk.

Usually, people who have had a stroke have high blood pressure, or hypertension. It is one of the most common risk factors for stroke.

However, there is also an association between long-term low blood pressure and stroke, including an increased risk of complications, such as gastrointestinal bleeding and sepsis.

It is also possible to have a ministroke, or transient ischemic attack (TIA), as a result of a sudden and sharp drop in blood pressure. This is known as a “low flow” TIA.

Treatment for low blood pressure is available. Keep reading to learn more about the link between low blood pressure and stroke.

Close-up of a manual blood pressure monitor.Share on Pinterest
Anneloes Beekman/EyeEm/Getty Images

Chronically low blood pressure raises the risk of stroke. Scientists are still learning about the relationship between the two, so it is unclear why this link exists.

Doctors measure blood pressure in millimeters of mercury (mm Hg). In a 2021 study, people with systolic blood pressure of less than 120 mm Hg, diastolic blood pressure of less than 60 mm Hg, and pulse pressure of at least 90 mm Hg were at a higher risk of dying from stroke compared with those with typical blood and pulse pressure.

People with systolic blood pressure below 120 mm Hg and at least one other health risk factor were at the highest risk of dying from stroke. These risk factors included:

Additionally, a study from 2018 looked at whether there was a link between orthostatic hypotension and stroke, dementia, and cognitive decline. Orthostatic hypotension is low blood pressure that occurs when a person stands up.

The researchers defined orthostatic hypotension as a drop in systolic blood pressure of at least 20 mm Hg or a drop in diastolic blood pressure of at least 10 mm Hg upon standing. People with orthostatic hypotension had double the risk of having an ischemic stroke compared with people without the condition.

A sharp drop in blood pressure can also cause a TIA, or ministroke, due to the temporary reduction in blood flow to the brain. This “low-flow” type of TIA is less common than other types.

A person should seek immediate medical attention if they or someone nearby begins to show symptoms of stroke. These include sudden:

  • numbness or weakness in the face, arms, or legs
  • confusion
  • difficulty speaking or understanding speech
  • difficulty seeing in one or both eyes
  • difficulty walking, dizziness, and balance or coordination problems
  • severe headache without a known cause

People with low blood pressure may also require medical attention in certain circumstances. If a person’s blood pressure drops too low, it may stop enough blood and nutrients from reaching their vital organs. This can lead to shock, which is a medical emergency. If a person develops the following symptoms, call 911:

  • cold and sweaty skin
  • rapid breathing
  • blue skin tone
  • weak and rapid pulse

According to a 2019 study, low blood pressure is uncommon in people who have acute ischemic strokes. High blood pressure is more common.

Other risk factors for ischemic stroke include:

Risk factors for hemorrhagic stroke include:

  • obesity
  • high alcohol consumption
  • smoking
  • lack of exercise
  • stress

The point at which low blood pressure becomes a risk factor may also be different between males and females.

A 2021 study in the journal Circulation examined sex differences in blood pressure in relation to cardiovascular disease. The researchers found that women had a lower blood pressure threshold than men for risk of stroke, as well as heart attack and heart failure.

Women with systolic blood pressure of 120–129 mm Hg had a similar risk of stroke as men with readings of 140–149 mm Hg.

Typical blood pressure is usually lower than 120/80 mm Hg for most adults, while low blood pressure is less than 90/60 mm Hg.

Most doctors only consider long-term low blood pressure to be dangerous if it causes obvious signs and symptoms, such as:

  • dizziness
  • lightheadedness
  • difficulty concentrating
  • cold or clammy skin
  • rapid or shallow breathing
  • blurred vision
  • nausea
  • fainting
  • fatigue
  • depression
  • dehydration or unusual thirst

Some people do not experience any symptoms because of their low blood pressure. In others, sitting down might relieve more minor symptoms.

A 2019 study noted that, in addition to raising the risk of stroke, low blood pressure may increase the risk of in-hospital complications after a stroke, such as:

Long-term low blood pressure can also cause:

  • Falls and related injuries: A 2019 systematic review and meta-analysis found a significant positive association between orthostatic hypotension and falls in older adults.
  • Shock: This condition commonly occurs in people with very low blood pressure, and it can be serious.

A doctor can diagnose low blood pressure using a blood pressure monitor. Alternatively, people can use one at home.

Treatment for low blood pressure depends on the underlying cause. For example, if the cause is dehydration or a lack of salt in the diet, a doctor may suggest drinking more fluids or electrolytes. If the cause is a medication, a doctor may be able to suggest a different dosage or an alternative drug.

Other strategies that may improve blood pressure include:

  • wearing compression socks or stockings
  • eating small, frequent meals
  • reducing or stopping alcohol consumption

Lifestyle changes may help significantly. However, some causes of low blood pressure are more serious or require more intensive treatment. These include:

  • internal bleeding
  • heart problems
  • infections

If a person has persistent or severe symptoms, they should speak with a doctor as soon as possible.

Research suggests that having low blood pressure increases a person’s risk of having a stroke or TIA and of dying from stroke. Low blood pressure is less common than high blood pressure in people with stroke, but it is still potentially harmful.

It is important to seek emergency medical attention if a person shows signs of stroke or dangerously low blood pressure.

In addition to a risk of stroke, low blood pressure may also cause falls or, in severe cases, shock. Anyone who experiences frequent symptoms because of their low blood pressure requires treatment.