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:
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High blood pressure medicines.
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Water pills (diuretics).
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Some heart medicines.
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Some antidepressants.
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Medicines for pain, anxiety, sedation, and sleep.
Other causes include:
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Dehydration from vomiting, diarrhea, or not getting enough fluids.
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Severe infection.
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High fever.
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Blood loss, such as bleeding from the stomach or intestines.
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Neurological diseases that affect the autonomic nervous system.
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Long bed rest.
Treatment will depend on what is causing your low blood pressure.
Home care
Follow these guidelines when caring for yourself at home:
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Rest until your symptoms get better.
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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. Take some slow deep breaths. This gives your body time to adjust to the change in position.
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Follow your doctor's treatment plan.
Follow-up care
Follow up with your doctor, or as advised.
When to get medical advice
Contact your doctor or seek medical care right away if any of these occur:
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Mild dizziness or lightheadedness
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Small amount of black or red color, or blood, in your stools or vomit
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Diarrhea or vomiting that doesn’t go away
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Not being able to eat or drink
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Fever of 100.4°F (38°C) or higher, or as advised by your doctor
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Burning feeling when you pee
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Bad-smelling pee
Call 911
Call 911, or get immediate medical care at the nearest emergency room if any of these occur:
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Fainting; or severe dizziness, confusion, or lightheadedness
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Large amount of black or red color, or blood, in your stools or vomit
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Chest pain or trouble breathing
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Feeling of racing heartbeats
