Haptoglobin is a liver protein that "catches" the free hemoglobin released into the blood when red cells are destroyed, and stops it from harming the kidneys.
Hence its main role: a low haptoglobin is a sign of hemolysis (breakdown of red cells). But it is also an acute-phase protein that rises with inflammation, and a component of liver fibrosis indices (for example, FibroTest).
Reference ranges
The reference range depends on the lab; approximate values:
| Normal | 0.3 – 2.0 g/L (30 – 200 mg/dL) |
| Low | hemolysis (breakdown of red cells) |
| High | inflammation, infection (an acute-phase protein) |
| In liver disease | may fall (reduced synthesis) |
What an elevated level means
A high haptoglobin is an acute-phase inflammatory response: it rises with infection, injury, flares of chronic disease, and after a heart attack.
A rise on its own is non-specific and is assessed together with other markers of inflammation (CRP). Remember: inflammation can "hide" hemolysis by keeping haptoglobin within the normal range.
What a low level means
A low haptoglobin is a key sign of hemolysis: when red cells break down it is quickly used up binding the released hemoglobin.
A low haptoglobin together with a raised indirect bilirubin and reticulocytosis confirms hemolytic anemia. Less often a fall occurs in severe liver disease (impaired synthesis).
How the test is done
Haptoglobin is measured in blood from a vein. When hemolysis is suspected it is checked together with hemoglobin, bilirubin, LDH and reticulocytes.
As a component of FibroTest, haptoglobin is also used for non-invasive assessment of liver fibrosis — there its fall contributes to the final index.
What affects the value
- Hemolysis (breakdown of red cells) — lowers haptoglobin.
- Inflammation and infection — raise it (acute phase).
- Severe liver disease — reduces synthesis.
- Transfusions and large hematomas — lower it.
- Estrogens and glucocorticoids — may raise it.
- Congenital deficiency (anhaptoglobinemia) — low without disease.
Assess liver fibrosis
Haptoglobin is part of FibroTest; assess your risk of liver fibrosis:
Frequently asked questions
What does a low haptoglobin mean?
Most often hemolysis — an accelerated breakdown of red cells: haptoglobin is used up binding the released hemoglobin. Together with a raised indirect bilirubin and reticulocytosis, a low haptoglobin confirms hemolytic anemia.
Why can haptoglobin be normal in hemolysis?
Haptoglobin is also an inflammatory protein. If there is infection or inflammation at the same time, they raise its production and can "mask" the fall in hemolysis. So the result is interpreted in the context of other measures.
Why is haptoglobin used in assessing the liver?
It is part of the non-invasive FibroTest index: in liver fibrosis haptoglobin synthesis falls, and this is factored into the calculation. This is how the extent of fibrosis is assessed indirectly from blood tests without a biopsy.
Related terms
Sources
- MedlinePlus (NIH) — Haptoglobin Blood Test
- Diagnostic value of serum haptoglobin (review). NCBI/PMC
- Haptoglobin Test — Testing.com