Haptoglobin in cats and dogs

What it shows

Haptoglobin has two jobs. It binds free haemoglobin — the pigment that escapes when red blood cells break inside the vessels — and the bound pair is removed from the blood; this also keeps iron away from bacteria. And it is a positive acute-phase protein: the liver makes more of it when there is inflammation, usually within one to two days.

In cats and dogs haptoglobin is a moderate acute-phase protein. Proteins of this group rise about five- to tenfold and peak around two to three days after the trigger — slower and less dramatically than the major ones, such as CRP and serum amyloid A in dogs. On protein electrophoresis haptoglobin sits in the alpha-2 band, and a strong rise can visibly lift the alpha-globulin fraction.

Higher than reference — what it may be a sign of

• Inflammation anywhere in the body — infection, tissue injury, tumours. The value says that inflammation is present, not where or why.
• Steroid hormones in dogs. Steroids switch on haptoglobin production, so dogs with high levels of their own steroid hormones or on steroid medicines have higher haptoglobin even without new inflammation. In a study of dogs with immune-mediated diseases, haptoglobin was significantly higher in dogs receiving steroids.
• Chronic disease in cats — reviews mention a rise in acute-phase proteins, including haptoglobin, in chronic kidney disease, inflammatory bowel disease and lymphoma.

Lower than reference

In theory, breakdown of red cells inside the vessels uses up haptoglobin: it binds the released haemoglobin and is cleared together with it, so the level falls. In practice this is not reliable on its own. In a study of dogs with immune-mediated haemolytic anaemia, haptoglobin stayed high in most of them — inflammation and steroid medicines can outweigh the loss. A falsely low value is possible if serum was stored at −20 °C, at which haptoglobin gradually decreases.

Look at together with

• CRP and serum amyloid A — faster, major acute-phase proteins (CRP and SAA in dogs, SAA in cats); haptoglobin adds a slower, longer view.
• Protein electrophoresis — a rise in the alpha-2 band may partly be haptoglobin.
• Haemoglobin, bilirubin and the Coombs test — when red-cell breakdown is suspected.
• Medicines — the vet notes whether the dog receives steroids before reading a high value.

Units and conversion

Labs report haptoglobin in g/L or mg/dL. One mg/dL equals 0.01 g/L, so 100 mg/dL is 1 g/L. The two units differ a hundredfold, so check which one is printed. In the app each row keeps the unit from the form; the chart converts to one unit so results from different labs line up.

Reference range

The reference range is on your lab’s form. Methods differ — some measure haptoglobin through its effect on haemoglobin, others with antibodies — and canine haptoglobin is much higher than in other species, so a test designed for another species has to be diluted for dog serum. Values from heparin plasma are higher than from serum. That is why results are best compared within one laboratory and method, and the trend over repeated tests says more than one number.

Cats and dogs

Sources

1. eClinPath (Cornell University College of Veterinary Medicine) — Acute phase proteins
2. Grobman M, Outi H, Rindt H, Reinero C. Serum thymidine kinase 1, canine C-reactive protein, haptoglobin, and vitamin D concentrations in dogs with immune-mediated hemolytic anemia, thrombocytopenia, and polyarthropathy. J Vet Intern Med, 2017
3. Gareis H, Schulz B. Evaluation of amyloid A and haptoglobin in the serum of cats with respiratory diseases. Frontiers in Veterinary Science, 2026