Low Blood Pressure

What is blood pressure?

Blood pressure is the force of the blood on the artery walls as the heart pumps blood through the body. The arteries are the blood vessels that carry blood from the heart to the rest of the body.

Blood pressure is measured in millimeters of mercury (mm Hg). Normal blood pressure ranges up to 120/80 mm Hg ("120 over 80"), but blood pressure can rise and fall with exercise, rest, or emotions. The first number (120 in this example) is the pressure when the heart pushes blood out to the rest of the body. It is called the systolic pressure. The second number (80 in this example) 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, or is low enough to cause symptoms. When blood pressure drops too low, the body may not get enough oxygen-rich blood. This may weaken breathing, movement, and brain function, and damage may occur.

How does it occur?

Low blood pressure can result from:

• medicine taken to treat high blood pressure, heart problems, or anxiety
• pregnancy
• low thyroid or low adrenal gland function
• dehydration
• lack of food
• standing too long in the heat
• shock due to loss of blood, a heart attack, or other conditions.

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

Low blood pressure is far less common than high blood pressure. However, some people, especially older adults, have postural or orthostatic hypotension. This is low blood pressure that can happen when you stand up after sitting or lying down. It happens when the body is not able to adjust blood pressure and blood flow fast enough for the change in position. Usually orthostatic hypotension lasts for only a few seconds or minutes after you stand up.

What are the symptoms?

Symptoms of low blood pressure may include:

• feeling tired
• dizziness, especially if you suddenly stand up
• fainting.

How is it diagnosed?

Blood pressure is checked at most healthcare visits. If your blood pressure is low and causing symptoms, your healthcare provider will ask about the symptoms, what you eat and drink, and if low blood pressure runs in your family. You should have your blood pressure taken after lying down for 10 minutes, then again after standing up, and again after standing and walking around for 5 minutes. You may be asked to use a portable blood-pressure measuring device, which will take your pressure at different times during day and night. You may also have urine and blood tests. You may have a chest X-ray and an electrocardiogram (ECG). All of this testing is done to look for a possible cause of the low blood pressure.

How is it treated?

Treating the cause usually corrects the low blood pressure. For example, if your blood pressure is low because of dehydration, you may be given fluids. If low blood pressure is caused by medicine, changing the dose of medicine may correct the problem. If a severe infection causes blood pressure to drop too low, treating the infection can return blood pressure to normal.

How can I help prevent low blood pressure?

If you have low blood pressure that is causing symptoms, try these tips:

• Avoid fasting.
• Avoid being out in the sun for a long time.
• Drink plenty of liquid every day.
• If you have been lying down, sit for a moment before standing up, and then stand up slowly. Stand a moment before walking. Walk in place briefly while pulling in your stomach muscles several times. (This helps the return of blood flow from the legs.)

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

If you have low blood pressure whenever you stand up and it bothers you, your provider can try several different medicines. You also can wear tight stockings over your feet and lower legs. These compression stockings help push blood back toward your heart.

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 card3635.htm Release 13/2010