Skip to content
Blood Test Tracker

Haptoglobin

A protein made by the liver that binds free hemoglobin. A low level can be a clue that red blood cells are breaking down faster than normal.

AI-verified against cited sources. Awaiting expert reviewAlso called HAPT, HaptoLOINC 4542-7

Check your result

Sex (optional)

Type your result to see where it falls.

Nothing you type here leaves your browser.

What it is

Haptoglobin is a protein made by your liver. When red blood cells break open, they spill hemoglobin into the blood. Haptoglobin attaches to that free hemoglobin so the body can clear it safely. The haptoglobin is used up in the process, so its level drops when many red cells are breaking down. Haptoglobin also rises with inflammation, so the result is always read with other tests.

Why it matters

Clinicians mostly use haptoglobin to look for the cause of anemia, especially when red blood cells may be breaking down (hemolysis). It is usually read together with LDH, bilirubin, a reticulocyte count and a blood smear. A low level does not prove hemolysis, and a normal level does not rule it out. Liver disease and a naturally low level can also lower haptoglobin, while inflammation can push it up.

If it’s low

A low level can be a sign of red blood cell breakdown, because haptoglobin is used up as it clears free hemoglobin. Other things can lower it too, including liver disease and an inherited low or missing haptoglobin. A low result is not always a sign of illness. Levels are often naturally low in children, and some healthy people have low or undetectable levels.

Common causes

  • Hemolysis, where red cells break down faster than the body replaces them (for example from an autoimmune process, an inherited red cell condition such as G6PD deficiency or sickle cell disease, or a transfusion reaction)
  • Children and teens, whose levels are often naturally low
  • An inherited low or missing haptoglobin (a gene variant that removes the haptoglobin gene)
  • Liver disease, such as cirrhosis
  • Poor nutrition (malnutrition)
  • Higher estrogen states, diluted blood or a mishandled sample

What can help

  • Ask whether your reticulocyte count, LDH, bilirubin and blood smear fit with red cell breakdown
  • Ask whether your liver tests could explain the result
  • Ask whether a low level has always been usual for you or for your family

If it’s high

A high haptoglobin level usually reflects inflammation. Haptoglobin is an acute-phase protein, which means it rises when the body is under stress. A high level is not a problem by itself. It can also hide hemolysis, because it can lift a falling level back into the usual range.

Common causes

  • Infection or other inflammation
  • Cigarette smoking
  • Steroid (corticosteroid) or androgen medicines
  • Nephrotic syndrome, a kidney condition that leaks protein into the urine

What can help

  • Ask whether the test should be repeated when you are well
  • If you have unexplained anemia, ask whether inflammation could be hiding red cell breakdown and which other tests make sense

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: 30–200 mg/dL. Source: ARUP Laboratories, MHCC Laboratory (catalog powered by Mayo Clinic Laboratories), University of Iowa Hospitals & Clinics, Michigan Medicine Clinical Laboratories (MLabs), Disease Markers, American Journal of Hematology, American Journal of Human Genetics, Nigerian Journal of Physiological Sciences, Scandinavian Journal of Clinical and Laboratory Investigation.

What can affect your result

  • Age: newborns and children often have low levels
  • Inherited differences, including a missing haptoglobin gene
  • Inflammation, infection and smoking raise it
  • Liver disease and poor nutrition lower it
  • Estrogen can lower it, and androgen and steroid medicines can raise it
  • Diluted blood or a damaged sample
  • Lab method: different assays give slightly different numbers
  • Inflammation, infection, cigarette smoking and nephrotic syndrome raise haptoglobin and can hide a drop caused by red cell breakdown.
  • Liver disease and poor nutrition lower it.
  • Higher estrogen states and diluted blood (hemodilution) can give a low result, and improper sample handling can too.
  • Androgen and corticosteroid medicines can raise it and may mask hemolysis.
  • A sample that is grossly hemolyzed (damaged in the tube) is rejected by ARUP.
  • On one immunoturbidimetric assay, extremely high levels (above 1,200 mg/dL) can read falsely low because of a hook effect.

Haptoglobin falls when red cells are breaking down, and in a review of autoimmune hemolytic anemia it was the last hemolysis marker to return to normal, so it can stay low for a while after the breakdown stops.

When to talk to a clinician

A low haptoglobin by itself is not an emergency. Get prompt care if you also have dark red, brown or cola-colored urine, yellow skin or eyes, back or belly pain, unusual paleness, a racing heart or shortness of breath, because these can happen when red blood cells break down quickly. Call 911 or your local emergency number for chest pain, fainting, confusion or severe trouble breathing.

Questions you could ask

  • Which tests are usually done together with haptoglobin to look at red cell breakdown?
  • Could inflammation or a medicine be raising my haptoglobin?
  • Would a repeat when I am well be useful?
  • Do my other blood tests suggest red blood cells are breaking down?
  • Could liver function, my age or a natural low level explain this?
  • Should we repeat it, and which other tests should go with it?

Questions people ask

My haptoglobin is low. Do I have hemolysis?

Not necessarily. A low level is one clue for red cell breakdown, but liver disease, a naturally low level, and sample or hydration problems can also cause it. Clinicians usually check other tests too, such as a reticulocyte count, LDH, bilirubin and a blood smear. In one study of 100 patients, a level of 25 mg/dL or less separated hemolytic from non-hemolytic conditions with 83% sensitivity and 96% specificity, so it is helpful but not perfect.

My haptoglobin is normal. Does that rule out hemolysis?

No. Haptoglobin rises with inflammation, infection, smoking and some medicines, which can lift a falling level back into the usual range. If hemolysis is suspected, clinicians look at several tests together.

How do I convert mg/dL to g/L?

Divide mg/dL by 100, so 30 to 200 mg/dL is 0.30 to 2.00 g/L. To go the other way, multiply g/L by 100.

Show the science and sources

Units

  • 1 mg/dL = 1 mg/dL
  • 1 mg/dL = 0.01 g/L

Open the Haptoglobin unit converter

Is a change real?

Haptoglobin naturally varies about 7.4% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 21% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: The European Biological Variation Study (EuBIVAS): a summary report.

For clinicians and researchers

Haptoglobin (Hp) is a hepatic alpha-2 glycoprotein that binds free hemoglobin with high affinity. The Hp–hemoglobin complex is cleared by macrophages through CD163, so Hp is consumed in intravascular hemolysis and, to a lesser extent, in extravascular hemolysis. Two common alleles (Hp1 and Hp2) give three phenotypes (1-1, 2-1, 2-2) with polymers of different size. In autoimmune hemolytic anemia, haptoglobin is the most sensitive hemolysis marker and the last to normalize. In a study of 100 patients, a cut-off of 25 mg/dL or less separated hemolytic from non-hemolytic disorders with 83% sensitivity and 96% specificity. Hp is also a positive acute-phase reactant and rises in inflammation, smoking and nephrotic syndrome. There is no single gold standard for hemolysis. Reported pitfalls include low values from cirrhosis, high-estrogen states, hemodilution and improper specimen handling, and normal or high values with androgens, corticosteroids and inflammation. Methods include immunoturbidimetry (ARUP, University of Iowa), nephelometry (Mayo, LOINC 46127-7), spectrophotometric binding assays and gel electrophoresis. A deletion of the Hp gene (Hpdel) causes anhaptoglobinemia when homozygous. In one family study Hp2/Hpdel carriers had a mean of 0.049 mg/mL against 1.64 mg/mL in healthy Hp2 volunteers, and an Hp1/Hpdel carrier had about half the level of Hp1 controls. A 2018 cohort of healthy Nigerians had markedly lower levels than usual reference intervals. A 2026 pediatric study of 355 neonates and children concluded haptoglobin has limited clinical value under about 13 to 15 years because levels are often naturally low and may fall below the assay's detection limit. The 30–200 mg/dL interval (0.30–2.00 g/L) is the one published by ARUP, Mayo and the University of Iowa, while Michigan Medicine prints 22–239 mg/dL. No published critical value was found.

LOINC 4542-7 (primary), 46127-7, 4543-5, 70209-2. Specimen: serum-or-plasma.

Sources

  1. Haptoglobin (test 0050280), ARUP Laboratories
  2. Haptoglobin, Serum (test HAPT), Mayo Clinic Laboratories, as listed in the MHCC Laboratory catalog, MHCC Laboratory (catalog powered by Mayo Clinic Laboratories)
  3. Haptoglobin (Pathology Handbook), University of Iowa Hospitals & Clinics
  4. Haptoglobin testing in hemolysis: measurement and interpretation, American Journal of Hematology (2014)
  5. Clinical Applications of Hemolytic Markers in the Differential Diagnosis and Management of Hemolytic Anemia, Disease Markers (2015)
  6. The haptoglobin-gene deletion responsible for anhaptoglobinemia, American Journal of Human Genetics (1998)
  7. Ahaptoglobinaemia in a Nigerian Cohort, Nigerian Journal of Physiological Sciences (2018)
  8. Reference intervals for haptoglobin in neonates and children 30 days to 18 years old, Scandinavian Journal of Clinical and Laboratory Investigation (2026)
  9. Haptoglobin (MLabs test information), Michigan Medicine Clinical Laboratories (MLabs)

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

Related markers