Hemoglobin is a protein inside red blood cells that carries oxygen from the lungs to tissues and organs within the body. Carbon dioxide is then transported back to the lungs from the body’s organs and tissues. A hemoglobin test can be performed alone or as a part of a complete blood count (CBC) test.

Why is the test performed?

Doctors typically order a hemoglobin test as part of a complete blood count (CBC) test to check a person’s overall health. A hemoglobin test can also be used to check for anemia, malnutrition, and dehydration. If a person is experiencing shortness of breath, dizziness, or fatigue, a test may be ordered to check for anemia or polycythemia vera.

What do the test results mean?

A normal hemoglobin range is:

  • 13.5 to 17.5 grams per deciliter for men
  • 12.0 to 15.5 grams per deciliter for women

If results are lower than normal, it means a person is anemic. There are several different causes of anemia, including:

  • Iron, Vitamin B-12, or Folate deficiency
  • Bleeding disorders
  • Certain cancers
  • Kidney or liver disease
  • Hypothyroidism
  • Thalassemia, a genetic disorder

Higher than normal results may be caused by:

  • Dehydration, sometimes caused by frequent vomiting or intense exercise
  • Lung disease
  • Smoking
  • Severe burns
  • High altitudes
  • Polycythemia vera

A doctor may order further tests to rule out other causes if a hemoglobin tests shows higher or lower than normal levels.