Hemoglobin

Hemoglobin is a protein in red blood cells. It carries oxygen from the lungs to cells throughout the body, and carries carbon dioxide from the cells to the lungs. A hemoglobin test measures the level of this protein in a sample of blood.

Who is a candidate for the test?

Often, this test is done as part of a complete blood count, or CBC. Or it may be done:

during pregnancy

during infancy

when a person has symptoms of anemia, such as lack of energy, pale skin, and shortness of breath

when a person is being treated for anemia

when family history or ethnic or racial background puts a person at risk for a blood disorder. Examples include hemoglobin disorders, sickle cell disease, and thalassemia.

How is the test performed?

Blood for the test is usually taken from a person's forearm. First, a tight band is put on the upper arm to make the veins swell below it. An area of skin on the forearm over the vein chosen is cleansed. Then a needle is inserted into the vein and a sample of blood is collected in a tube.
Occasionally blood is taken from another site, such as a finger or heel. If so, the skin is cleansed and pricked with a sharp tool called a lancet. Drops of blood are collected in a tiny tube. The blood is analyzed at a lab.