What Is Low Blood Pressure and Is It Dangerous?

How to know when low blood pressure is a problem

Woman checking blood pressure in living room
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First of all, "low blood pressure" is not strictly defined. While high blood pressure has clear numerical definitions, low blood pressure is not defined by a universally accepted value. In the past, some attempts were made to standardize the meaning of low blood pressure, but no official set of guidelines is currently supported by any medical authority.

Defining Low Blood Pressure

Low blood pressure is referred to in medical terms as hypotension. Generally speaking, doctors sometimes refer to a blood pressure of 90/60 as a rough rule of thumb for hypotension when evaluating patients because experience seems to show that this is the point at which symptoms may develop.

Low Blood Pressure Usually Isn't a Problem

In general, if you have no history of medical problems and you're not experiencing any symptoms, a low blood pressure reading is not a cause for concern. If you discover on your own that your blood pressure is below 120/80, you should mention it to your doctor during your next visit but you probably don’t need to schedule a special appointment unless you know that the low reading represents a significant change from your average blood pressure.

Symptoms of Low Blood Pressure

If your blood pressure is usually low and you experience any of these symptoms, be sure to let your healthcare provider know:

  • Nausea
  • Feeling lightheaded or dizzy
  • Fainting
  • Being excessively thirsty and/or dehydrated
  • Exhaustion
  • Blurry vision
  • An inability to concentrate
  • Depression

Low Blood Pressure Can Be Dangerous

With very few exceptions, chronic blood pressure below 120/80 is not dangerous. Low blood pressure is usually considered dangerous only when it causes the symptoms mentioned above or results from sudden blood pressure decreases.

In cases where your blood pressure drops suddenly, it isn’t actually the low blood pressure itself that causes the danger, but rather the sudden change from a higher value to a lower value.

Sudden changes in blood pressure can cause interruptions in the blood supply to your heart, kidneys, and brain, and will almost always be accompanied by distinctive symptoms. An example of this situation is orthostatic hypotension, where changes in your body's position, usually a change from sitting to standing, is accompanied by a rapid drop in blood pressure. Usually, sudden episodes of low blood pressure are a sign that something else might be wrong, and are typically an indication for a full medical workup.

Shock

If you have low blood pressure due to shock, this is a medical emergency that must be dealt with immediately. Symptoms of shock include:

  • Confusion
  • Pale or blue, cold, clammy skin
  • Weak or fast pulse
  • Rapid breathing and/or an inability to breathe deeply

Other Causes of Low Blood Pressure

There are other potential causes and conditions behind low blood pressure besides the ones mentioned above. They include:

  • Pregnancy
  • Losing a lot of blood
  • Being dehydrated
  • Heart conditions like heart failure, heart attack, low heart rate, and valve issues
  • Infection in your bloodstream, called septicemia
  • Severe allergic reaction, called anaphylaxis
  • Thyroid conditions or diabetes
  • Nutritional deficiencies
  • Medications like diuretics, beta blockers, certain antidepressants, alpha blockers, and medications for erectile dysfunction and Parkinson's disease

Treatment for Low Blood Pressure

The kind of treatment you receive for low blood pressure depends on what's going on. If you don't have any symptoms, it's unlikely that you'll need treatment. However, if you're experiencing symptoms and your doctor can't find an underlying health problem that explains your low blood pressure, he or she will work with you to get your blood pressure higher in order to alleviate your symptoms.

This could include one or more of the following:

  • Increasing your salt intake
  • Wearing compression stockings
  • Drinking more water
  • Medication, especially if you have orthostatic hypotension
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