What is a Hemoglobin Test?
A hemoglobin test measures the levels of hemoglobin in your blood. Hemoglobin is a protein in your red blood cells that carries oxygen from your lungs to the rest of your body. If your hemoglobin levels are abnormal, it may be a sign that you have a blood disorder.
Other names: Hb, Hgb
What is it used for?
A hemoglobin test is often used to check for anemia, a condition in which your body has fewer red blood cells than normal. If you have anemia, the cells in your body don't get all the oxygen they need. Hemoglobin tests are measured as part of a complete blood count (CBC).
Why do I need a hemoglobin test?
Your health care provider may order the test as part of a routine exam, or if you have:
- Symptoms of anemia, which include weakness, dizziness, and cold hands and feet
- A family history of thalassemia, sickle cell anemia, or other inherited blood disorder
- A diet low in iron and other minerals
- A long-term infection
- Excessive blood loss from an injury or surgical procedure
What happens during a hemoglobin 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.
Will I need to do anything to prepare for the test?
You don't need any special preparation for a hemoglobin test. If your health care provider has ordered other tests on your blood sample, you may need to fast (not eat or drink) for several hours before the test. Your health care provider will let you know if there are any special instructions to follow.
Are there any risks to the test?
There is very little risk to having a blood test. After the test, some people experience mild pain, dizziness, or bruising. These symptoms usually go away quickly.
What do the results mean?
There are many reasons your hemoglobin levels may not be in the normal range.
Low hemoglobin levels may be a sign of:
- Different types of anemia
- Iron deficiency
- Liver disease
- Cancer and other diseases
High hemoglobin levels may be a sign of:
- Lung disease
- Heart disease
- Polycythemia vera, a disorder in which your body makes too many red blood cells. It can cause headaches, fatigue, and shortness of breath.
If any of your levels are abnormal, it doesn't always mean you have a medical condition that needs treatment. Diet, activity level, medicines, a menstrual period, and other factors can affect the results. You may also have higher than normal hemoglobin levels if you live in a high altitude area. Talk with your provider to learn what your results mean.
Learn more about laboratory tests, reference ranges, and understanding results.
Is there anything else I need to know about a hemoglobin test?
Some forms of anemia are mild, while other types of anemia can be serious and even life threatening if not treated. If you are diagnosed with anemia, be sure to talk to your health care provider to find out the best treatment plan for you.
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- Hsia C. Respiratory Function of Hemoglobin. New England Journal of Medicine [Internet]. 1998 Jan 22 [cited 2017 Feb 1]; 338:239–48. Available from: http://www.nejm.org/doi/full/10.1056/NEJM199801223380407
- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Anemia; [cited 2022 Jan 4]; [about 2 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/anemia/
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- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Polycythemia Vera; [cited 2022 Jan 4]; [about 14 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/polycythemia-vera
- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Anemia; [cited 2022 Jan 4]; [about 2 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/anemia
- Scherber RM, Mesa R. Elevated Hemoglobin or Hematocrit Level. JAMA [Internet]. 2016 May [cited 2017 Feb 1]; 315(20):2225-26. Available from: http://jamanetwork.com/journals/jama/article-abstract/2524164
- Testing.com [Internet]. Seattle (WA): OneCare Media; c2022. Hemoglobin; [modified 2021 Nov 9; cited 2022 Jan 4]; [about 11 screens]. Available from: https://www.testing.com/tests/hemoglobin/
- University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2022. Health Encyclopedia: Hemoglobin; [cited 2022 Jan 4] [about 4 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=hemoglobin
The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.