What is a blood hemoglobin test?

The blood hemoglobin test means checking the amount of hemoglobin in the blood. Hemoglobin is a protein in red blood cells that carries oxygen to the organs and tissues of the body and sends carbon dioxide from your organs and tissues back to the lungs.

If the hemoglobin test shows that your hemoglobin level is lower than normal, it means that your red blood cell count is lower. There can be a variety of causes of lower hemoglobin levels, including vitamin deficiencies, bleeding and chronic diseases.

If the hemoglobin test shows more than normal levels, there are several possible causes – blood disorders polycythemia vera (stem cell cancer), smoking, and dehydration.

Blood hemoglobin may need to be tested for various reasons:

Your doctor may test your hemoglobin as part of a complete blood count during regular medical examinations to monitor the general health of the body and for various ailments such as anemia.

If the body feels weak, tired, short of breath or dizzy, the doctor may recommend a hemoglobin test. These signs and symptoms can lead to anemia. Hemoglobin tests help diagnose other medical conditions.


The normal range of hemoglobin is:

  • For men, 13.5 to 17.5 grams per deciliter.

  • For women, 12.0 to 15.5 grams per deciliter.

The general range for children varies with age and gender. The range of a normal hemoglobin level may differ from one to another in medical practice.

Less than normal result:

If your hemoglobin level is lower than normal, then you have anemia. There are many forms of anemia, each with different causes, including:

  • Iron deficiency
  • Vitamin-B-12 deficiency
  • Folate deficiency
  • Bleeding
  • Cancers that affect the bone marrow, such as leukemia
  • Kidney disease
  • Liver disease
  • Hypothyroidism
  • Thalassemia (a genetic disorder)

More than normal results:

If your hemoglobin level is higher than normal, it can result in:

  • Polycythemia vera (stem cell cancer)
  • Lung disease
  • Dehydration
  • Living too high
  • Heavy smoking
  • burn
  • Excessive vomiting
  • Extreme physical exercise

If your hemoglobin level is below or above normal, the doctor will do a hemoglobin test with other tests or additional tests may be needed to determine the next steps.