Hb, Hgb, H and H, Hemoglobin and hematocrit
This is a blood test to find out how much hemoglobin is in your blood. Hemoglobin is the main part of your red blood cells. Hemoglobin is made up of a protein called globin and a compound called heme. Heme consists of iron and a pigment called porphyrin, which gives your blood its red color.
Hemoglobin serves the important role of carrying oxygen and carbon dioxide through your blood. If your hemoglobin is too low, you may not be able to supply the cells in your body with the oxygen they need to survive.
You may need this blood test as part of routine blood testing. You may also need to have your hemoglobin checked if you have anemia or symptoms of anemia. Anemia can be caused by blood loss, decreased production of red blood cells, or increased destruction of red blood cells. Your doctor can use your hemoglobin test to help find the cause of your anemia. These are other reasons you may need this test:
To diagnose a disease that causes anemia
To see how severe your anemia is
To see whether your anemia is responding to treatment
To evaluate a disease called polycythemia
Symptoms of anemia may include:
Shortness of breath
Cold, pale skin
Polycythemia is a disease that causes your body to make too many red blood cells. Polycythemia may cause:
Hemoglobin is usually tested as part of a complete blood count, or CBC. A CBC is a blood test that counts all the different cells in your blood. A hemoglobin test may also be paired with a hematocrit test. The hematocrit blood test tells what percent of your blood is made up by red blood cells.
A result for a lab test may be affected by many things, including the method the laboratory uses to do the test. If your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with your health care provider.
Hemoglobin measurement is given in grams per deciliter (g/dL). Normal hemoglobin is different for men, women, and children. Here are the normal values:
12 to 16 g/dL for women
14 to 17.4 g/dL for men
9.5 to 24.5 g/dL for children, depending on the child's age. If your child is having this test, you should discuss the results with your child's doctor.
High hemoglobin levels can be caused by polycythemia, heart failure, and chronic obstructive pulmonary disease. Low hemoglobin may be caused by:
Cancer and other diseases
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, or feeling dizzy. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
Your hemoglobin may be affected by several factors:
Living at high altitudes may make hemoglobin go up.
Certain drugs can make hemoglobin go down or up.
An extreme amount of exercise can make hemoglobin go up.
Pregnancy may make hemoglobin go down.
Taking in too much fluid can make hemoglobin go down.
You don't need to prepare for this test. Make sure to tell your doctor about:
Any chance you are pregnant
Any extreme exercising you have been doing
In addition, be sure your doctor knows about all medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illicit drugs you may use.