Low Blood Pressure Not Normally a Cause for Concern

John Graves, M.D., Nephrology/Hypertension, Mayo Clinic

DEAR MAYO CLINIC:

I know having high blood pressure is not good for your health, but what about low blood pressure? I have always been told that I have low blood pressure which I thought was OK until my last appointment when the nurse seemed concerned. What could be causing this and is this something I can or should correct, and if so, how? I'm a 41-year-old woman in good health.

ANSWER:

Unless it causes troublesome symptoms, low blood pressure (hypotension) usually isn't a cause for concern and doesn't require treatment. If low blood pressure begins to cause symptoms that interfere with your daily activities, though, talk to your doctor about ways it can be managed. In rare cases, low blood pressure can be a sign of an underlying medical condition.

Blood pressure is a measurement of the pressure in the arteries during the active and resting phases of each heartbeat. The top number in a blood pressure reading is the systolic pressure. This is the amount of pressure the heart generates when pumping blood through the arteries to the rest of the body. The bottom number in a blood pressure reading is the diastolic pressure. It refers to the amount of pressure in the arteries when the heart is at rest between beats.

Blood pressure is considered normal in adults if it's approximately 120/80 millimeters of mercury (mm Hg). Many experts think 115/75 is optimal. A systolic blood pressure reading of 90 mm Hg or less or a diastolic blood pressure of 60 mm Hg or less is generally considered low blood pressure.

Keep in mind, though, that low blood pressure is based more on function than numbers. If your blood pressure is in the low range, but you feel well and can go about your daily activities without trouble, then whatever your blood pressure measure is, that's normal for you.

Generally, an adult has more difficulty functioning well when systolic blood pressure goes below 100. The farther down systolic blood pressure goes from there, the more difficult it is to function normally. Low blood pressure can cause disruptive symptoms such as dizziness, light-headedness, blurred vision, lack of concentration and fainting. If severe and prolonged, low blood pressure can also cause heart attack and stroke.

People who have low blood pressure most often experience symptoms when they change body positions, particularly when moving from lying down or sitting to standing. This happens because when you stand up, gravity causes blood to pool in your legs. When less blood circulates back to the heart, the heart has less blood to pump throughout the body, and blood pressure falls. In people who already have low blood pressure, the additional decrease in fluid available to the heart to pump into the circulation can trigger symptoms.

If symptoms are mild, no treatment is typically required. If they are moderate to severe, your doctor may recommend treatment. Symptoms of low blood pressure are most frequently provoked by dehydration. To remedy this, you may need to increase the amount of water you drink. Extra fluids increase blood volume and help prevent dehydration. Your doctor may also suggest you add salt to your diet.

If additional water and salt don't decrease symptoms, medications are available that can help raise blood pressure, either by boosting blood volume or restricting the ability of blood vessels to dilate which can lower blood pressure. In some cases, wearing compression stockings may also help reduce the pooling of blood in the legs.

Rarely, low blood pressure can be a sign of a medical condition that requires treatment. Some conditions that may cause low blood pressure include diabetes, heart problems and thyroid disorders. In addition, anemia, a condition in which the body doesn't produce enough red blood cells, may also cause low blood pressure.

In the situation you describe, it's unlikely that your low blood pressure requires treatment. But you should continue to have your blood pressure monitored regularly. If you begin to develop symptoms that may be related to low blood pressure, make an appointment to see your doctor and have them evaluated. -- John Graves, M.D., Nephrology/Hypertension, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care.

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Low Blood Pressure Not Normally a Cause for Concern