Haptoglobin
- Also Known As:
- HPT
- Hemoglobin-binding Protein
- Hp

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.At a Glance
Why Get Tested?
To help detect and evaluate hemolytic anemia
When To Get Tested?
When you have signs of anemia such as weakness, paleness, or jaundice, which is yellowing of the skin and whites of the eyes, that a healthcare practitioner suspects may be due to red blood cell destruction (hemolytic anemia)
Sample Required?
A blood sample drawn from a vein
Test Preparation Needed?
None
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Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.
The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.
If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.
Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.
While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”
For more information, please read the article Reference Ranges and What They Mean.
What is being tested?
Haptoglobin is a protein produced by the liver that the body uses to clear free hemoglobin (found outside of red blood cells) from circulation. This test measures the amount of haptoglobin in the blood.
Hemoglobin is the iron-containing protein complex that transports oxygen throughout the body. It is normally found within red blood cells (RBCs) and very little is found free circulating in the blood. Haptoglobin binds to free hemoglobin in the blood. This forms a haptoglobin-hemoglobin complex that is rapidly cleared out of circulation by the liver so that it can be broken down and the iron recycled. Formation of the haptoglobin-hemoglobin complex also prevents hemoglobin from being filtered by the kidneys and passed into the urine, which can be toxic to the kidneys.
However, when an increased number of RBCs are damaged and/or break apart (hemolysis), they release their hemoglobin into the blood, increasing the amount of free hemoglobin in circulation. When large numbers of RBCs are destroyed, haptoglobin levels in the blood will temporarily decrease as the haptoglobin is used up faster than the liver can produce it. A decrease in the amount of haptoglobin may be a sign that you have a condition that is causing red blood cells to be destroyed or to break apart. When the binding capacity of haptoglobin is exceeded, the free hemoglobin level in circulation goes up and may cause tissue damage and/or organ dysfunction due to oxidative stress of free hemoglobin.
Increased RBC destruction may be due to inherited or acquired conditions. Some examples include transfusion reactions, certain drugs, and mechanical breakage, such as may be seen with some prosthetic heart valves. The destruction may be mild or severe, occurring suddenly (acute) or developing and lasting over a long period of time (chronic), and it can lead to hemolytic anemia. People with hemolytic anemia may experience symptoms such as fatigue, weakness, and shortness of breath and their skin may be pale or yellowed, also called jaundice.
Liver disease may also result in decreased haptoglobin levels as liver damage may inhibit both the production of haptoglobin and the clearing of the haptoglobin-free hemoglobin complexes.
Common Questions
View Sources
Sources Used in Current Review
2020 Review completed by Hoda Hagrass, MD, Ph.D., Medical Director of clinical chemistry and immunology laboratories, UAMS.
Haptoglobin (HP) Test. MedlinePlus. Available online at https://medlineplus.gov/lab-tests/haptoglobin-hp-test/ Accessed on 8/25/2020.
Andersen C., Torvund-Jensen M., Nielsen M., et al. Structure of the haptoglobin–haemoglobin complex. Nature 489, 456–459 (2012). Available online at https://doi.org/10.1038/nature11369. Accessed August 2020.
Shih AW, McFarlane A, Verhovsek M. Haptoglobin testing in hemolysis: measurement and interpretation. Am J Hematol. 2014;89(4):443-447. doi:10.1002/ajh.23623.
John V. Mitsios. Distinguishing In Vivo Versus In Vitro Hemolysis. CLN Ask the Expert: December 2018. Available online at https://www.aacc.org/publications/cln/articles/2018/december/distinguishing-in-vivo-versus-in-vitro-hemolysis. Accessed on 8/26/2020.
Contemporary Practice in Clinical Chemistry. William Clarke and Mark Marzinke. 4th Edition, AACC Press, Elsevier.
RE Langlois M, Delanghe J. Clin Chem 1996;42:1589-1600.
Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO. Pp 466-467.
(© 2005). Haptoglobin. ARUP’s Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.aruplab.com/guides/clt/tests/clt_291a.jsp#4273706.
Dhaliwal, G. et. al. (2004 June 1). Hemolytic Anemia. American Family Physician [On-line journal]. Available online at http://www.aafp.org/afp/20040601/2599.html.
Nanda, R., Updated (2005 February 1). Haptoglobin. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003634.htm.
(© 1995-2005). Autoimmune Hemolytic Anemia. Merck Manual-Second Home Edition [On-line information]. Available online at http://www.merck.com/mmhe/sec14/ch172/ch172f.html?qt=haptoglobin&alt=sh.
O-Hara Paggen, M. (1999 September 1). HELLP Syndrome: Recognition and Perinatal Management. American Family Physician [On-line journal]. Available online at http://www.aafp.org/afp/990901ap/829.html.
Sibai, B. (2004 May). Diagnosis, Controversies, and Management of the Syndrome of Hemolysis, Elevated Liver Enzymes, and Low Platelet Count. ACOG, High-Risk Pregnancy Series: An Expert’s View v 103 (5 part 1). [On-line journal]. Available online at http://www.mccn.edu/library/ABOG/2005/PMID15121574.pdf#search=’test%20haptoglobin’.
Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry, AACC Press, Washington, DC. Pp 199.
Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 512-513.
Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition]. Pp 840.
Levin, M. (2007 March 8). Haptoglobin. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003634.htm . Accessed on 11/23/08.
(2006 September). What is Hemolytic Anemia? National Heart Lung and Blood Institute [On-line information]. Available online at http://www.nhlbi.nih.gov/health/dci/Diseases/ha/ha_whatis.html. Accessed on 11/23/08.
Schick, P. (2007 January 29). Hemolytic Anemia. eMedicine [On-line information]. Available online at http://www.emedicine.com/med/TOPIC979.HTM. Accessed on 11/23/08.
Gersten, T. (Updated 2012 February 8). Haptoglobin. MedlinePlus Medical Encyclopedia. [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003634.htm. Accessed August 2012.
(© 1995–2012). Haptoglobin, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/9168. Accessed August 2012.
Lichtin, A. (Revised 2009 February). Overview of Hemolytic Anemia. Merck Manual for Healthcare Professionals [On-line information]. Available online through http://www.merck.com. Accessed August 2012.
(2011 April 1). What is Hemolytic Anemia? National Heart Lung and Blood Institute [On-line information]. Available online at http://www.nhlbi.nih.gov/health/health-topics/topics/ha/. Accessed August 2012.
Schick, P. (Updated 2011 August 8). Hemolytic Anemia. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/201066-overview. Accessed August 2012.
(2008 November). Haptoglobin (HP) Genotyping. ARUP Laboratories Technical Bulletin [On-line information]. Available online through https://www.aruplab.com. Accessed August 2012.
Cook, J. et. al. (Updated 2011 July). Hemolytic Anemias. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/HemolyticAnemias.html?client_ID=LTD#tabs=0. Accessed August 2012.
2016 review performed by Shawn Clinton, Ph.D., DABCC, Laboratory Director and the Testing.com Editorial Review Board.
(February 2, 2014) Gersten T. Hemolytic anemia. MedlinePlus Medical Encyclopedia. Available online at https://www.nlm.nih.gov/medlineplus/ency/article/000571.htm. Accessed May 2016.
(Updated: March 21, 2014) NIH National Heart Lung and Blood Institute. What is Hemolytic Anemia? Available online at https://www.nhlbi.nih.gov/health/health-topics/topics/ha/diagnosis. Accessed May 2016.
Henry’s Clinical Diagnosis and Management by Laboratory Methods, 21st Edition, Pg. 237, by Richard A. McPherson MD MSc (Author), Matthew R. Pincus MD PhD (Author).
Kristiansen M1, Graversen JH, Jacobsen C, Sonne O, Hoffman HJ, Law SK, Moestrup SK. Identification of the haemoglobin scavenger receptor. Nature. 2001 Jan 11;409(6817):198-201.
Wintrobe’s Clinical Hematology. 12th ed. Greer J, Foerster J, Rodgers G, Paraskevas F, Glader B, Arber D, Means R, eds. Philadelphia, PA: Lippincott Williams & Wilkins: 2009, Pg 800.
Harmening D. Clinical Hematology and Fundamentals of Hemostasis, Fifth Edition, F.A. Davis Company, Philadelphia, 2009, Pg 177.
(November 15, 2015) Schick P. Hemolytic Anemia Workup. Medscape Reference. Available online at http://emedicine.medscape.com/article/201066-workup. Accessed May 2016.
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