What is a haemoglobin test?
A haemoglobin test measures the levels of haemoglobin in your blood. Haemoglobin is a protein in your red blood cells that carries oxygen from your lungs to the rest of your body. If your haemoglobin levels are abnormal, it may be a sign that you have a blood disorder.
Other names: Hb, Hgb
What is it used for?
A haemoglobin test is often used to check for anaemia, a condition in which your body has fewer red blood cells than normal. If you have anaemia, your cells don’t get all the oxygen they need. Haemoglobin tests are also frequently performed with other tests, such as:
- Hematocrit, which measures the percentage of red blood cells in your blood
- Complete blood count, which measures the number and type of cells in your blood
Why do I need a haemoglobin test?
Your health care provider may have ordered the test as part of a routine exam, or if you have:
- Symptoms of anaemia, which include weakness, dizziness, pale skin, and cold hands and feet
- A family history of thalassemia, sickle cell anaemia, or other inherited blood disorder
- A diet low in iron and minerals
- A long-term infection
- Excessive blood loss from an injury or surgical procedure
What happens during a haemoglobin 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 preparations for a haemoglobin test. If your health care provider has also ordered other blood tests, 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 of having a blood test. You may have slight pain or bruise at the spot where the needle was put in, but most symptoms usually go away quickly.
What do the results mean?
There are many reasons your hemoglobin levels may be outside the normal range.
Low hemoglobin levels may be a sign of:
- Different types of anaemia
- Thalassemia
- 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 does not necessarily indicate a medical problem needing treatment. Diet, activity level, medications, a women’s menstrual cycle, and other considerations can affect the results. In addition, you may have higher than normal haemoglobin if you live in a high altitude area. Talk to your health care provider to learn what your results mean.
Is there anything else I need to know about a haemoglobin test?
Some forms of anaemia are mild, while other types of anaemia can be serious and even life-threatening if not treated. If you are diagnosed with anaemia, be sure to talk to your health care provider to find out the best treatment plan for you.
References
- Aruch D, Mascarenhas J. Contemporary approach to essential thrombocythemia and polycythemia vera. Current Opinion in Hematology [Internet]. 2016 Mar [cited 2017 Feb 1]; 23(2):150–60. Available from: https://www.ncbi.nlm.nih.gov/pubmed/26717193
- 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
- Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Hemoglobin; [updated 2017 Jan 15; cited 2017 Feb1]; [about 3 screens]. Available from: https://labtestsonline.org/understanding/analytes/hemoglobin/tab/test
- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Anemia: Overview [; cited 2019 Mar 28]; [about 3 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/anemia
- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Types of Blood Tests; [updated 2012 Jan 6; cited 2017 Feb 1]; [about 4 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests#Types
- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Risks of Blood Tests? [updated 2012 Jan 6; cited 2017 Feb 1]; [about 5 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests#Risk-Factors
- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Signs and Symptoms of Polycythemia Vera? [updated 2011 Mar 1; cited 2017 Feb 1]; [about 4 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; What Do Blood Tests Show? [updated 2012 Jan 6; cited 2017 Feb 1]; [about 4 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests
- National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What is Anemia? [updated 2012 May 18; cited 2017 Feb 1]; [about 3 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
- University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2017. Health Encyclopedia: Total Bilirubin (Blood); [cited 2017 Feb 1] [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid;=hemoglobin
