ESR (erythrocyte sedimentation rate) in cats and dogs

What it shows

Red blood cells normally repel one another and sink slowly. During inflammation the liver releases acute-phase proteins — fibrinogen among them — and together with some antibodies they make red cells stick into stacks (rouleaux). Stacks are heavier and settle faster, so the clear plasma column above the cells grows quicker.

The classic Westergren method reads the column after one hour in an upright pipette of citrated blood. Automated devices use EDTA blood from the blood-count tube and, for dogs and cats, give a result in about 14 minutes. Either way ESR is a non-specific marker: it is read together with other tests, never on its own.

Higher than reference — what it may be a sign of

• Inflammation: acute or ongoing inflammation, abscesses, fever. In a study of dogs, more than half of those with acute or subacute inflammation had a raised ESR.
• Infections: in dogs vector-borne diseases such as ehrlichiosis, babesiosis, leishmaniosis and heartworm disease; in cats FeLV, FIV and calicivirus infection.
• Chronic kidney disease in both species, and urinary tract disorders.
• Tumours — ESR can rise, but not in a way that points to a tumour specifically.
• Anaemia: the fewer red cells, the faster they settle, so a low hematocrit raises ESR by itself. A correction for hematocrit has been proposed, but results with it are contradictory.
• Large red cells (macrocytosis) can also speed up settling.

Lower than reference

A low ESR is rarely important on its own. It can come from an excess of red cells (erythrocytosis) or from small or misshapen cells — microcytosis, spherocytes and other abnormal shapes settle more slowly. Lists of medicines that lower ESR, such as anti-inflammatory and steroid drugs, come from human medicine — these are human data, not data from dogs and cats.

Look at together with

• CRP in dogs and SAA in cats — the most widely used inflammation markers. They and ESR complement each other: in chronic disease or during follow-up CRP may rise less, while ESR stays high as long as inflammation lasts.
• Hematocrit — anaemia alone can push ESR up, so a high ESR with a low hematocrit is read with care.
• Fibrinogen and globulins — the proteins that make red cells stack.
• White cell count and neutrophils — in dogs ESR was not linked to the total white count and only weakly to neutrophils, so the two give different information.

Units and conversion

ESR is given in mm/h (мм/ч on Russian forms) — millimetres of clear plasma above the settled cells after one hour. Automated devices that read earlier convert their result to the same unit. Nothing needs converting, but the method matters: values from the classic method and from an automated device are not directly interchangeable, so a trend is followed on one method.

Reference range

The reference range is on your lab’s form, and here it depends strongly on the method. In dogs published intervals include 0–5 mm/h by the classic method and 1–8 mm/h on an automated device read at 14 minutes. One teaching hospital set its own upper limit at 14 mm/h, above the manufacturer’s 10 mm/h, because its healthy dogs often ran slightly higher. For cats data are scarce: 0–5 mm/h in an older source and 1–23 mm/h in a study of 52 healthy cats.

Cats and dogs

Sources

1. Diamanti D, Pieroni C, Pennisi MG, Marchetti V, Gori E, Paltrinieri S, Lubas G. The Erythrocyte Sedimentation Rate (ESR) in Veterinary Medicine: A Focused Review in Dogs and Cats. Animals (Basel). 2025;15(2):246.
2. Paltrinieri S, Ferrari R, Scavone D, Pieroni C, Diamanti D, Tagliasacchi F. Increased Erythrocyte Sedimentation Rate in Dogs: Frequency in Routine Clinical Practice and Association with Hematological Changes. Animals. 2024;14(10):1409.
3. Uva A, Cavalera MA, Gusatoaia O, et al. Inflammatory Status and Chronic Kidney Disease in Cats: Old and New Inflammatory Markers — A Pilot Prospective Study. Animals. 2023;13(23):3674.