Why is hypotension bad

The heart pumps blood around the body, continuously delivering oxygen and other nutrients. Blood pressure refers to the force of blood pushing against the artery walls as the heart pumps. In a person with low blood pressure, blood flows through the veins and arteries with too little force. Doctors use two figures to denote blood pressure. The first refers to systolic blood pressure, which is the force of the blood against artery walls when the heart beats.

The second refers to diastolic blood pressure, which is the force of the blood when the heart rests between beats. Healthcare professionals measure blood pressure readings in millimeters of mercury mm Hg.

It is possible to have low blood pressure without any symptoms. However, some people with this issue may experience :. Blood pressure also declines with age, and some people have naturally low blood pressure due to genetic factors. Some temporary causes, such as pregnancy, resolve on their own.

Others may require dietary changes and other care or management strategies. Some potentially more severe health issues can also cause low blood pressure, including :. Low blood pressure may sometimes result from alcohol use or the use of certain medications, such as :.

To address low blood pressure, a doctor may adjust the dosage of an existing drug or recommend medications to increase blood pressure. What's considered low blood pressure for you may be normal for someone else. Most doctors consider blood pressure too low only if it causes symptoms.

Some experts define low blood pressure as readings lower than 90 mm Hg systolic or 60 mm Hg diastolic. If either number is below that, your pressure is lower than normal.

A sudden fall in blood pressure can be dangerous. A change of just 20 mm Hg — a drop from systolic to 90 mm Hg systolic, for example — can cause dizziness and fainting when the brain fails to receive enough blood. And big drops, such as those caused by uncontrolled bleeding, severe infections or allergic reactions, can be life-threatening. Doctors often break down low blood pressure hypotension into categories, depending on the causes and other factors.

Some types of low blood pressure include:. Low blood pressure on standing up orthostatic or postural hypotension. This is a sudden drop in blood pressure when you stand up from a sitting position or after lying down. Gravity causes blood to pool in your legs when you stand.

Ordinarily, your body compensates by increasing your heart rate and constricting blood vessels, thereby ensuring that enough blood returns to your brain. But in people with orthostatic hypotension, this compensating mechanism fails and blood pressure falls, leading to dizziness, lightheadedness, blurred vision and even fainting. Orthostatic hypotension can occur for various reasons, including dehydration, prolonged bed rest, pregnancy, diabetes, heart problems, burns, excessive heat, large varicose veins and certain neurological disorders.

You may have blurry vision, a headache, neck or back pain, nausea, or heart palpitations. Sitting down may relieve these symptoms. When this happens, low blood pressure can lead to shock , which requires immediate medical attention.

Signs of shock include cold and sweaty skin, rapid breathing, a blue skin tone, or a weak and rapid pulse. If you notice signs of shock in yourself or someone else, call Your doctor will use a blood pressure test to diagnose low blood pressure. Other tests may include blood, urine, or imaging tests and a tilt table test if you faint often. You may not need treatment for low blood pressure.

Depending on your signs and symptoms, treatment may include drinking more fluids, taking medicines to raise your blood pressure, or adjusting medicines that cause low blood pressure. Recommended lifestyle changes include changing what and how you eat and how you sit and stand up. Your doctor may also recommend compression stockings if you have to stand for long periods. Visit Low Blood Pressure for more information about this topic. We are committed to advancing science and translating discoveries into clinical practice to promote the prevention and treatment of heart, lung, blood, and sleep disorders, including problems associated with low blood pressure.

Learn about current and future NHLBI efforts to improve health through research and scientific discovery. Learn about the following ways the NHLBI continues to translate current research into improved health for people with abnormally low blood pressure.

Learn about some of the pioneering research contributions we have made over the years that have improved clinical care. In support of our mission , we are committed to advancing research on low blood pressure in part through the following ways. We lead or sponsor research on low blood pressure. See whether you or someone you know is eligible to participate in our clinical trials. Learn more about participating in a clinical trial. View all trials from ClinicalTrials. Low blood pressure There is no set figure at which blood pressure is said to be low, as this can vary from person to person.

What is blood pressure? The top figure - the systolic blood pressure - is a measure of the pressure when your heart muscle is contracted and pumping blood. This is the maximum pressure in your arteries. The bottom figure - the diastolic blood pressure - is the pressure between heart beats when the heart is resting and filling with blood.

This is the minimum pressure in your arteries. When is low blood pressure a problem? This is often due to one of the following problems: Postural hypotension also called orthostatic hypotension. This is when your blood pressure drops when you stand up from a sitting or lying position. Normally, the veins in your legs will automatically constrict become narrower when you stand up, preventing blood from pooling in your legs and forcing it back to your heart.

If you have postural hypotension however, this doesn't happen. This means the blood remains in your legs, leading to a lack of blood reaching your brain. Postprandial hypotension. This is when your blood pressure drops after eating a meal.

It is thought to be due to blood pooling in the blood vessels within your abdomen as your meal is being digested. Symptoms of low blood pressure If your blood pressure is naturally low, you are unlikely to get any symptoms and will probably feel completely well.

Causes If you consistently have a low blood pressure, this may be completely normal for you. Causes include: taking drugs to treat high blood pressure hypertension - especially drugs called diuretics and alpha blockers acute illnesses that cause severe blood loss or damage to the heart diseases involving the nerves that control the veins in your legs diabetes - as diabetes can also damage the nerves a disease of the adrenal gland Addison's disease - this can cause a loss of salt from your body, resulting in low blood pressure early stages of pregnancy loss of blood due to serious injury or loss of fluid due to burns You are also more likely to get postural hypotension as you get older.

Diagnosis If you have a naturally low blood pressure, you will probably only find out when having your blood pressure measured as part of a general checkup, or while having tests for some other reason. Measuring blood pressure Blood pressure is measured using a device called a sphygmomanometer.