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Dizziness (Dizzy) (cont.)

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What causes dizziness?

While classifying dizziness into lightheadedness and vertigo categories may help understand how the body works, sometimes it is worthwhile to review common reasons why people might complain of dizziness.

Low blood pressure as a cause of dizziness

Dizziness, lightheadedness, and the feeling of passing out is a common complaint in people who have low blood pressure. When the blood pressure is too low, not enough oxygen-rich blood is being delivered to the brain, and its function can be affected. If the brain's blood supply is decreased too much, the person may pass out (syncope). Symptoms may worsen when changing position from lying down or sitting, to standing up.

In addition to feeling dizzy, associated symptoms may include:

Low blood pressure may be the result of an underlying illness or disease, or it may be a normal physiologic condition. Some common reasons for low blood pressure include the following:

  • Anemia (decreased red blood cell count) due to decreased production or increased destruction of red blood cells
  • Bleeding may cause anemia due to red blood cell loss
  • Dehydration (loss of water in the body) often occurs with infections that cause vomiting and diarrhea. Fever also can cause a significant amount of water loss due to increased metabolic rate and excessive sweating as the body tries to cool itself.
  • Heat-related illnesses associated with dehydration such as heat cramps, heat exhaustion, or heat stroke (a medical emergency).
  • Side effects of certain medications used to control blood pressure and heart rate. Examples include:
    • beta blockers (propranolol [Inderal, Inderal LA], atenolol [Tenormin], metoprolol, [Lopressor, Toprol XL]), which block adrenalin receptors in the heart and may limit the ability of the heart rate to increase in response to changes of position, decreased red blood cell count, or dehydration.
    • Nitroglycerin and isosorbide mononitrate (Imdur), a long acting nitroglycerin, are medications that are prescribed to dilate blood vessels in the heart to treat angina. However, these medications also cause other blood vessels in the body to dilate, decreasing blood pressure.
    • Diuretics that can cause dehydration
    • ACE inhibitors that slow the heart rate, and
    • Medications for erectile dysfunction (sildenafil [Viagra, Revatio], tadalafil [Cialis], and vardenafil [Levitra, Staxyn ODT], avanafil [Stendra]) that can dilate blood vessels.
  • Alcohol use
  • Pregnancy
Medically Reviewed by a Doctor on 8/4/2016


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