Interpreting a feline hemogram: the 5 classic pitfalls
Published on June 15, 2026 · 3 min read
The hemogram is the most prescribed test in feline medicine. It is also the one that generates the most interpretation errors, because the cat is neither a small dog nor a miniature human. Here are the five pitfalls we most often hear about from the field.
Pitfall 1: platelet clumping
Feline blood clots fast. Very fast. A slightly difficult puncture, a poorly mixed tube, and your platelets clump before they even reach the analyzer. The result: an artefactual thrombocytopenia displayed at 80,000/µl in a perfectly healthy cat.
The reflex: for any feline thrombocytopenia, check the smear. Platelet clumps at the feathered edge confirm the artefact. A clean draw, on a calm cat, in a properly filled and immediately mixed EDTA tube, solves the problem in most cases.
Pitfall 2: stress lymphocytosis
A cat stressed by transport and restraint can double its lymphocyte count within minutes: the adrenaline surge demarginates lymphocytes. A lymphocytosis at 12,000/µl in a terrified kitten is nothing pathological.
The reflex: always interpret the feline white line in the context of the draw. A follow-up at a distance, on a settled animal, avoids many unnecessary work-ups.
Pitfall 3: anemia masked by dehydration
A cat in chronic kidney disease often arrives dehydrated. Dehydration concentrates the blood and artificially raises the hematocrit. The anemia, though very real, only appears after rehydration.
The reflex: in any dehydrated patient, re-read the hematocrit after volume correction. A "normal" hematocrit on admission can hide an anemia at 22% the next day.
Pitfall 4: unsuitable reference ranges
Reference intervals vary with counting technology. Comparing today's result to values from another laboratory, obtained on another technology, leads to wrong conclusions.
The reflex: monitor your patients on the same analyzer, with the same intervals. This is one of the concrete benefits of in-house testing: the consistency of serial results. An analyzer like the MS4S2, designed for veterinary hematology and used both in practice and in research institutes, provides species-specific intervals.
Pitfall 5: the result without a smear
No analyzer, whatever its technology, replaces the clinician's eye on a smear when the result is abnormal. Heinz bodies, erythrocyte parasites, blasts: the smear remains the confirmation test.
The reflex: the three-minute rule. Every abnormal hemogram deserves three minutes under the microscope before any therapeutic decision.
What happens before the analyzer
Four of the five pitfalls above are settled at the moment of sampling, not at the moment of reading. It is worth saying so to the team: the quality of a feline blood count is decided in the consulting room.
A calm cat, restrained without a struggle, ideally not transported that same morning. A clean stick, first time, with a needle suited to the animal's size. An EDTA tube filled to the mark, no more and no less, since an underfilled tube concentrates the anticoagulant and damages the cells. Immediate mixing, by gentle inversion rather than shaking.
Then the delay. A tube run within the hour gives results the same tube will no longer give the next day: leukocytes degrade, platelets clump, red cells swell. That is a practical argument for testing on site, quite apart from any question of cost.
In summary
The feline hemogram is read methodically: sample quality first, clinical context next, confirmation smear in case of anomaly. Performed in-house, on a machine whose intervals you know, it becomes a monitoring tool of remarkable precision — and a result handed to the client during the consultation.
Frequently asked questions
By the smear. Platelet clumps at the feathered edge mean aggregation, which is very common in cats because feline blood clots fast. A clean stick on a calm animal, into a properly filled EDTA tube mixed straight away, solves most cases.
A question about your equipment?
Answer within 24 business hours, with a personalized profitability study, no commitment.
Request information