Hemoglobin test

A hemoglobin test measures the amount of hemoglobin in your blood.

Hemoglobin is a protein in your red blood cells that carries oxygen to your body's organs and tissues and transports carbon dioxide from your organs and tissues back to your lungs.

If a hemoglobin test reveals that your hemoglobin level is lower than normal, it means you have a low red blood cell count (anemia). Anemia can have many different causes, including vitamin deficiencies, bleeding and chronic diseases.

If a hemoglobin test shows a higher than normal level, there are several potential causes — the blood disorder polycythemia vera, living at a high altitude, smoking, dehydration, burns and excessive vomiting.

Why it's done How you prepare What you can expect Results

You may have a hemoglobin test for several reasons:

  • To check your overall health. Your doctor may test your hemoglobin as part of a complete blood count during a routine medical examination to monitor your general health and to screen for a variety of disorders, such as anemia.
  • To diagnose a medical condition. Your doctor may suggest a hemoglobin test if you're experiencing weakness, fatigue, shortness of breath or dizziness. These signs and symptoms may point to anemia or polycythemia vera. A hemoglobin test may help diagnose these or other medical conditions.
  • To monitor a medical condition. If you've been diagnosed with anemia or polycythemia vera, your doctor may use a hemoglobin test to monitor your condition and guide treatment.

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