Hypotension (HI-po-TEN-shun) is abnormally low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood.
Blood pressure is measured as systolic (sis-TOL-ik) and diastolic (di-a-STOL-ik) pressures. "Systolic" refers to blood pressure when the heart beats while pumping blood. "Diastolic" refers to blood pressure when the heart is at rest between beats.
You most often will see blood pressure numbers written with the systolic number above or before the diastolic number, such as 120/80 mmHg. (The mmHg is millimeters of mercury—the units used to measure blood pressure.)
Normal blood pressure in adults is lower than 120/80 mmHg. Hypotension is blood pressure that's lower than 90/60 mmHg.
Blood pressure doesn't stay the same all the time. It lowers as you sleep and rises when you wake up. Blood pressure also rises when you're excited, nervous, or active.
Your body is very sensitive to changes in blood pressure. For example, if you stand up quickly, your blood pressure may drop for a short time. Your body adjusts your blood pressure to make sure enough blood and oxygen are flowing to your brain, kidneys, and other vital organs.
Most forms of hypotension happen because your body can't bring blood pressure back to normal or can't do it fast enough.
Some people have low blood pressure all the time. They have no signs or symptoms, and their low blood pressure is normal for them.
In other people, certain conditions or factors cause abnormally low blood pressure. As a result, less blood and oxygen flow to the body's organs.
For the most part, hypotension is a medical concern only if it causes signs or symptoms or is linked to a serious condition, such as heart disease. Signs and symptoms of hypotension may include dizziness, fainting, cold and sweaty skin, fatigue (tiredness), blurred vision, or nausea (feeling sick to your stomach).
In extreme cases, hypotension can lead to shock.
In a healthy person, low blood pressure without signs or symptoms usually isn't a problem and needs no treatment. If it causes signs or symptoms, your doctor will try to find and treat the condition that's causing it.
Hypotension can be dangerous. It can make you fall because of dizziness or fainting. Shock, a severe form of hypotension, is a condition that's often fatal if not treated right away. With prompt and proper treatment, shock can be successfully treated.