Low blood pressure isn't always a concern. But sometimes hypotension can cause dizziness and fainting or be life-threatening. Learn when it's treated.
Low blood pressure is generally considered a blood pressure reading lower than 90 millimeters of mercury (mm Hg) for the top number (systolic) or 60 mm Hg for the bottom number (diastolic).
What's considered low blood pressure for one person might be OK for someone else. Low blood pressure might cause no noticeable symptoms, or it might cause dizziness and fainting. Sometimes, low blood pressure can be life-threatening.
The causes of low blood pressure range from dehydration to serious medical conditions. It's important to find out what's causing low blood pressure so that it can be treated, if necessary.
Types of low blood pressure include:
Low blood pressure (hypotension) symptoms may include:
For some people, low blood pressure may be a sign of an underlying health condition, especially when it drops suddenly or occurs with symptoms.
A sudden fall in blood pressure can be dangerous. A change of just 20 mm Hg — a drop from 110 mm Hg systolic to 90 mm Hg systolic, for example — can cause dizziness and fainting. And big drops, such as those caused by uncontrolled bleeding, severe infections or allergic reactions, can be life-threatening.
Extreme low blood pressure can lead to a condition known as shock. Symptoms of shock include:
If you have symptoms of extreme low blood pressure (hypotension) or shock, seek emergency medical help.
Most health care providers consider blood pressure to be too low only if it causes symptoms. Occasional minor dizziness or lightheadedness can be caused by many things, such as spending too much time in the sun or in a hot tub. It's important to see a health care provider to get a correct diagnosis.
If you have consistently low blood pressure readings but feel fine, your provider may just monitor you during routine health checkups. It can be helpful to keep a record of your symptoms, when they occur and what you're doing at the time.
Blood pressure is determined by the amount of blood the heart pumps and the amount of resistance to blood flow in the arteries. A blood pressure measurement is given in millimeters of mercury (mm Hg). It has two numbers:
The American Heart Association categorizes ideal blood pressure as normal. An ideal blood pressure is usually lower than 120/80 mm Hg.
Blood pressure varies throughout the day, depending on:
Blood pressure is usually lowest at night and rises sharply on waking. Certain health conditions and use of medications may cause low blood pressure.
Medical conditions that can cause low blood pressure include:
Some medications can cause low blood pressure, including:
Anyone can have low blood pressure (hypotension). Risk factors for hypotension include:
Potential complications of low blood pressure (hypotension) include:
Severely low blood pressure can reduce the body's oxygen levels, which can lead to heart and brain damage.
To diagnose low blood pressure (hypotension), your health care provider will do a physical exam and ask questions about your medical history. The exam includes measuring blood pressure.
Other tests may be done to determine the cause of low blood pressure.
Someone having a tilt table test begins by lying flat on a table. Straps hold the person in place. After lying flat for a while, the table is tilted to a position that mimics standing. The health care provider watches how the heart and the nervous system that controls it respond to the changes in position.
Low blood pressure (hypotension) without symptoms or with only mild symptoms rarely requires treatment.
If low blood pressure is causing symptoms, the treatment depends on the cause. For instance, if medication causes low blood pressure, your health care provider may recommend changing or stopping the medication or lowering the dose. Don't change or stop taking your medication without first talking to your care provider.
If it's not clear what's causing low blood pressure or no treatment exists, the goal is to raise blood pressure and reduce symptoms. Depending on age, health and the type of low blood pressure, there are several ways to do this:
Medications. Several drugs are available to treat low blood pressure that occurs when standing up (orthostatic hypotension). For example, the drug fludrocortisone boosts blood volume. It's often used to treat orthostatic hypotension.
If you have long-term (chronic) orthostatic hypotension, midodrine (Orvaten) may be prescribed to raise standing blood pressure levels. This drug reduces the ability of the blood vessels to expand, which raises blood pressure.
Compression stockings, also called support stockings, press on the legs, improving blood flow. A stocking butler may help with putting on the stockings.
Depending on the reason for low blood pressure, the following steps might help reduce or prevent symptoms.
Pay attention to body positions. Gently move from lying flat or squatting to a standing position. Don't sit with legs crossed.
If symptoms of low blood pressure begin while standing, cross the thighs like a pair of scissors and squeeze. Or put one foot on a ledge or chair and lean as far forward as possible. These moves encourage blood flow from the legs to the heart.
Eat small, low-carb meals. To help prevent blood pressure from dropping sharply after meals, eat small meals several times a day. Limit high-carbohydrate foods such as potatoes, rice, pasta and bread.
A health care provider also might recommend drinking one or two strong cups of caffeinated coffee or tea with breakfast. Caffeine can cause dehydration, however, so be sure to drink plenty of water and other fluids without caffeine.
No special preparations are necessary to have your blood pressure checked. Don't stop taking medications you think might affect your blood pressure without a health care provider's advice.
Here's some information to help you get ready for your appointment.
Make a list of:
For low blood pressure, basic questions to ask your provider include:
Don't hesitate to ask other questions.
Your provider is likely to ask you questions, including: