Low Blood Pressure

What is blood pressure?

Blood pressure is the pressure of the blood against the walls of the blood vessels during and after each beat of the heart. Blood pressure can rise and fall with exercise, rest, or emotions. Normal blood pressure ranges up to 120/80 ("120 over 80"). The upper number (120) is the pressure when the heart pushes blood out to the rest of the body (systolic pressure). The bottom number (80) is the pressure when the heart rests between beats (diastolic pressure).

What is low blood pressure?

Low blood pressure (hypotension) usually means blood pressure that is lower than 90/60 in younger adults, or is low enough to cause symptoms. When blood pressure drops too low there is danger of the body not getting enough oxygen-rich blood. Breathing, movement, and brain function can be weakened and damage can occur.

Low blood pressure is far less common than high blood pressure. However, some older adults develop postural or orthostatic hypotension. When they stand up, the blood tends to pool in the legs and cause very low blood pressure. (The upper number drops by 20 or the lower number drops by 10.)

How does it occur?

Low blood pressure can result from:

medicine taken to treat high blood pressure, heart problems, or anxiety
pregnancy
diabetes
low thyroid or low adrenal gland function
dehydration
lack of food
standing too long in the heat
being in shock (from stroke or a severe allergic reaction).

Rapid drops in blood pressure that threaten life can occur due to loss of blood, severe infections, or low body temperature due to cold exposure.

What are the symptoms?

Symptoms of low blood pressure may include:

feeling tired
dizziness, especially if you suddenly stand up.

How is it diagnosed?

Blood pressure is checked at most health care visits. Low blood pressure is usually discovered during one of these visits. Your health care provider will ask about your symptoms, what you eat and drink, and if low blood pressure runs in your family. You may have urine and blood tests. Your provider may order a chest x-ray and an electrocardiogram (ECG). You may be asked to use a portable blood-pressure measuring device, which will take your pressure at different times during day and night. All of this testing is done to look for a possible cause of your low blood pressure.

How is it treated?

Treating the cause usually corrects the low blood pressure. For example, giving fluids will stop low blood pressure due to dehydration. If low blood pressure is caused by medicine, changing the dose of medicines may correct the problem. If a severe infection causes blood pressure to drop too low, treating the infection can return blood pressure to normal.

What can I do to prevent low blood pressure?

Try these tips:

Avoid fasting.
Avoid long periods in the sun.
Drink plenty of liquid every day.
Sit for a moment before standing and stand a moment before walking.
Stand up slowly from lying down or sitting.
Walk in place briefly while pulling in your stomach muscles several times. (This aids the return of blood flow from the legs.)

Tell your health care provider if you have any symptoms after you start taking a new medicine. Regular exams by your health care provider may detect low blood pressure before it becomes a health problem.

Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.

HIA File CRD3635F.HTM Release 9.0/2006