Topic Overview

What is low blood pressure?

Low blood pressure means that your blood pressure is lower than normal. Another name for low blood pressure is hypotension (say “hy-poh-TEN-shun”).

In most healthy adults, low blood pressure does not cause problems or symptoms. In fact, it may be normal for you. For example, people who exercise regularly often have lower blood pressure than people who are not as fit.

But if your blood pressure drops suddenly or causes symptoms like dizziness or fainting, it is too low. It can cause shock. Shock can be dangerous if it is not treated right away.

Blood pressure is a measure of how hard the blood pushes against the walls of your arteries as it moves through your body. Blood pressure consists of two numbers: systolic and diastolic.

• The systolic (higher) number shows how hard the blood pushes when the heart is pumping.
• The diastolic (lower) number shows how hard the blood pushes between heartbeats, when the heart is relaxed and filling with blood.

Someone with a systolic pressure of 120 and a diastolic pressure of 80 has a blood pressure of 120/80, or "120 over 80." Normal blood pressure is lower than 120/80.

Low blood pressure does not have a specific number where it is too low. Most doctors consider blood pressure to be too low when it causes symptoms or drops suddenly. In general, low blood pressure symptoms happen when blood pressure is less than 90/60.

What causes low blood pressure?

Some of the causes of low blood pressure include:

• Getting up after you sit or lie down. This can cause a quick drop in blood pressure called orthostatic hypotension.
• Standing for a long time.
• Not drinking enough fluids (dehydration).
• Medicines, such as high blood pressure medicine or other heart medicines.
• Health problems such as thyroid disease, severe infection, bleeding in the intestines, or heart problems.
• Trauma, such as major bleeding or severe burns.

What are the symptoms?

Many people with low blood pressure don’t have any symptoms.

Symptoms to watch for include:

• Feeling dizzy, lightheaded, or faint.
• Having a fast or irregular heartbeat.
• Feeling sick to your stomach or vomiting.
• Feeling more thirsty than usual.
• Having blurry vision.
• Feeling weak.
• Being confused.
• Being tired.
• Having cold, clammy skin.
• Breathing very fast.
• Having black, tarry stools.
• Having a fever.

If you have symptoms of low blood pressure, especially dizziness or fainting, call your doctor.