A blood pressure reading is made up of 2 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. However, any drop in blood pressure greater than 40 mmHg from your normal baseline may be considered low blood pressure for you. Generally, the lower the blood pressure you have the better. However, it becomes 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 is significant. This drop in blood pressure can cause dizziness, lightheadedness, or fainting. Orthostatic hypotension is most commonly related to low blood volume or an abnormal neurological reflex. It's also more common as we age. However, it can be a sign of an underlying illness that may need further tests.
Some medicines can cause orthostatic hypotension. These include:
High blood pressure medicines
Water pills (diuretics)
Some heart medicines
Pain, anxiety, sedative, and sleep medicines
Other causes include:
Dehydration from vomiting, diarrhea, or not getting enough fluids
Blood loss, such as bleeding from the stomach or intestines
Neurological diseases that affect the autonomic nervous system
Treatment will depend on what is causing your low blood pressure.
Follow these guidelines when caring for yourself at home:
Rest until your symptoms get better.
Change positions slowly from lying to standing. When getting out of bed, sit on the side of the bed with your legs down for at least 30 seconds before standing. This gives your body time to adjust to the position change.
Follow the treatment plan described by your healthcare provider.
Follow up with your healthcare provider, or as advised.
Call your healthcare provider right away if any of these occur:
Mild dizziness or lightheadedness
Small amount of black or red color, or blood, in your stools or vomit
Diarrhea or vomiting that doesn’t go away
Not being able to eat or drink
Fever of 100.4°F (38°C) or higher, or as advised by your provider
Burning feeling when you pee
Fainting; or severe dizziness or lightheadedness
Large amount of black or red color, or blood, in your stools or vomit
Abnormal chest pain or trouble breathing