Orthostatic Low Blood Pressure (Hypotension)

A blood pressure reading is made up of two numbers that are measured in millimeters of mercury (mmHg). There is a top number over a bottom number. The top number is the systolic pressure. The bottom number is the diastolic pressure. A normal blood pressure is a systolic pressure less than 120 mmHg over a diastolic pressure less than 80 mmHg. Low blood pressure, or hypotension, is generally defined as a systolic blood pressure less than 90 mmHg. But any drop in blood pressure of more than 40 mmHg from your normal baseline may be low blood pressure for you. Most of the time, the lower the blood pressure you have, the better. But it can be a problem when it becomes too low and causes symptoms.

Orthostatic hypotension is a type of low blood pressure that occurs only when you change position from lying or sitting to standing. Any drop in systolic pressure of 20 mmHg or diastolic pressure of 10 mm Hg when standing can be a problem. It can cause dizziness, lightheadedness, or fainting. This type of low blood pressure is most often related to low blood volume or an abnormal neurological reflex. It's also more common as we age. But it can be a sign of an underlying illness, so you may need more tests.

Some medicines can cause orthostatic hypotension. These include:

• High blood pressure medicines.

• Water pills (diuretics).

• Some heart medicines.

• Some antidepressants.

• Medicines for pain, anxiety, sedation, and sleep.

Other causes include:

• Dehydration from vomiting, diarrhea, or not getting enough fluids.

• Severe infection.

• High fever.

• Blood loss, such as bleeding from the stomach or intestines.

• Neurological diseases that affect the autonomic nervous system.

• Long bed rest.

Treatment will depend on what is causing your low blood pressure.