Hemoglobin Test
Reviewed
Also called: Hb, Hgb, H&H
A hemoglobin test measures the levels of hemoglobin in your blood. Hemoglobin is an iron-rich protein in your red blood cells.
Specimen: Blood (from a vein in your arm)
Why this test may be ordered
- As part of a routine exam
- If you have symptoms of anemia, such as weakness, dizziness, and cold hands and feet
- If you have a family history of thalassemia, sickle cell anemia, or other inherited blood disorder
- If you have a diet low in iron and other minerals
- If you have a long-term infection or excessive blood loss from an injury or surgical procedure
Preparation and collection
You don't need any special preparation for a hemoglobin test. If your provider has ordered other blood tests, you may need to fast (not eat or drink) for several hours before the test.
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
Your results will compare your hemoglobin level to the normal range, which may be called the reference range. This range may vary, based on the laboratory used and your age, race, and sex. The test can't tell you what's causing an abnormal level.
What does low hemoglobin mean?
Low hemoglobin level: Low hemoglobin levels may be a sign of: Different types of anemia, Thalassemia, Iron deficiency, Liver disease, Cancer and other diseases, Blood loss from injury, a heavy menstrual period, or other problems, Lack of certain nutrients, such as iron or vitamin B-12. Limitation: If any of your levels are abnormal, it doesn't always mean you have a medical condition that needs treatment. Next step: If you are diagnosed with anemia, talk to your provider about the best treatment plan for you.What does high hemoglobin mean?
High hemoglobin level: High hemoglobin levels may be a sign of: Lung disease, Heart disease, Polycythemia vera, a disease which causes your bone marrow to make too many red blood cells, Sleep apnea, a disorder that causes you to repeatedly stop breathing during sleep. Limitation: Living at a higher altitude can also cause a high hemoglobin level. Next step: Talk with your provider if you have questions about your results.
- The test cannot tell you what is causing an abnormal level.
- Abnormal results do not always mean you have a medical condition that needs treatment.
- Results can be affected by diet, activity level, medications, dehydration, smoking, certain genetic conditions, and living at a high altitude.
What to do next
Talk with your provider if you have questions about your results. If you are diagnosed with anemia, talk to your provider about the best treatment plan for you.
- Do you have symptoms of anemia such as weakness, dizziness, or cold hands and feet?
- Do you have a family history of thalassemia, sickle cell anemia, or other inherited blood disorders?
- Do you have a diet low in iron or other minerals?
- Do you have a long-term infection?
- Have you had excessive blood loss from an injury or surgical procedure?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.