A feline CBC is 7 numbers that only mean something in pairs. A hematocrit of 22 percent is mild anemia in a dehydrated cat and serious anemia in a well hydrated one. A white cell count of 21 x 10^9/L is inflammation in a sick cat and a stress leukogram in a frightened one. Read the rows against each other, then against the cat in front of you.
The 7 rows on the report
Most in-house analyzers and reference laboratories report the same core panel: white cell count, red cell count, hemoglobin, hematocrit, mean cell volume, mean cell hemoglobin concentration, and platelet count. A reticulocyte count is added when anemia is present, and it is the single most useful add-on because it separates a marrow that is responding from one that is not. Typical feline intervals are below; your laboratory's own numbers govern.
| Row (unit) | Lower limit | Upper limit | Read it as |
|---|---|---|---|
| WBC (x 10^9/L) | 5.5 | 19.5 | High: inflammation, stress. Low: virus, marrow suppression |
| RBC (x 10^12/L) | 6.5 | 12.0 | High: dehydration. Low: anemia, blood loss |
| Hemoglobin (g/dL) | 8.0 | 15.0 | High: hemoconcentration. Low: anemia, iron loss |
| Hematocrit (percent) | 24 | 45 | High: water loss. Low: anemia under 24 |
| MCV (fL) | 39 | 55 | High: regeneration. Low: iron deficiency, shunt |
| MCHC (g/dL) | 30 | 36 | High: lipemia, hemolysis. Low: regeneration |
| Platelets (x 10^9/L) | 175 | 500 | High: inflammation, rebound. Low: clumping, immune loss |
Read the red cell rows as one group
Hematocrit, red cell count and hemoglobin rise and fall together, so 3 abnormal rows usually describe 1 problem. A hematocrit of 50 percent with total protein of 8.5 g/dL and a history of 2 days of vomiting is dehydration, not polycythemia. A hematocrit of 18 percent with a normal total protein points to blood loss or hemolysis rather than dilution. Cats also run lower hematocrits than dogs: 24 to 45 percent is normal, and a value of 30 percent in a 12 year old cat deserves a look at the trend rather than a diagnosis.
MCV and MCHC tell you what kind of anemia. A rising MCV with a rising reticulocyte count over 3 to 5 days is regeneration, meaning the marrow works. A low MCV with a low MCHC suggests iron deficiency, often from slow blood loss through the gut. A normal MCV with a normal MCHC and no reticulocytes is the pattern of chronic kidney disease, chronic inflammation or marrow disease, and that is the pattern that needs the most work to explain.
What a high value means
Above 50 percent hematocrit, think water loss first: vomiting, diarrhea, fever, or a cat that has not drunk for 2 days. True polycythemia is rare and usually comes with a hematocrit above 60 percent, brick red gums and a normal total protein. A white cell count above 19.5 x 10^9/L is inflammation until proven otherwise, and the differential matters more than the total: neutrophilia with a left shift and toxic change points to bacterial infection, while neutrophilia with lymphopenia and eosinopenia in a calm cat is the classic stress leukogram of corticosteroids or fear.
A platelet count above 500 x 10^9/L is usually reactive, seen 1 to 2 weeks after blood loss, during inflammation, or after surgery. Values above 1000 x 10^9/L are uncommon and worth a smear review.
What a low value means
Hematocrit under 24 percent is anemia and needs a reticulocyte count the same day. Under 15 percent, or any anemia with weakness, collapse or a heart rate above 240 beats per minute in a kitten, is an emergency. A white cell count under 5.5 x 10^9/L is more worrying than a high one in cats, because it can signal feline panleukopenia, FeLV or FIV related marrow suppression, or sepsis with consumption. Platelets under 175 x 10^9/L need a smear before a diagnosis: clumping in the tube is the most common cause and is not disease at all.
Neutropenia under 2.5 x 10^9/L with fever is a reason to hospitalize rather than recheck in a week, since cats can consume neutrophils faster than the marrow replaces them.
3 abnormal combinations that change the plan
First combination: low hematocrit plus high reticulocytes. That is regenerative anemia, and the two main causes are blood loss and immune mediated hemolysis. Look for a bleeding site, check the urine, and ask whether the gums are pale or yellow. Second combination: low hematocrit plus reticulocytes under 0.5 percent. That is non-regenerative anemia, and the shortlist is chronic kidney disease, chronic inflammation, FeLV or FIV, and marrow disease. Third combination: high white cell count plus a left shift plus toxic neutrophils. That is active inflammation or infection and usually means imaging plus a culture rather than a repeat blood test.
A fourth pattern is worth knowing because it is so often misread: low platelets plus a normal smear is a clumping artifact in 1 out of every few samples, so a count of 80 x 10^9/L with no bruising is rechecked in a citrate tube before anything else happens.
4 feline quirks that distort the numbers
- Stress raises neutrophils and lowers lymphocytes within 30 to 60 minutes of a car ride.
- Platelet clumps form in under 2 minutes in some samples, dropping the count by 50 percent or more.
- Dehydration raises hematocrit by 5 to 10 points and hides mild anemia.
- Kittens under 12 weeks run lower hematocrits and higher white cell counts than adults.
What to ask your vet about the report
Ask 4 things. Was a reticulocyte count run, and was it the aggregate or the punctate type, since only aggregate reticulocytes indicate recent regeneration in cats. Was the sample a venous draw or an ear prick, and how long did it sit before analysis. Was the smear reviewed by a person, because analyzer platelet counts are the least reliable number on the page. And what is the trend over the last 2 or 3 tests, since a hematocrit falling from 38 to 30 percent over 6 months means more than a single value of 30 percent.
Recheck intervals that make sense
Stable mild anemia with a normal reticulocyte response: recheck in 2 to 4 weeks. Non-regenerative anemia: recheck in 1 to 2 weeks with kidney and thyroid values. Neutropenia with fever: recheck in 24 to 48 hours, not 7 days. Platelet count under 50 x 10^9/L: same day, with a smear. Any single abnormal row in an otherwise well cat: repeat in 2 to 4 weeks before building a diagnosis on 1 number.
Reference intervals differ between analyzers and laboratories, so compare your cat against the range printed on its own sheet. For background on why white cells behave this way, see white cell counts in cats, and for how anemia and hydration interact, see feline vision and the eye exam that often comes with a blood pressure check.
Terms mentioned in this article
Frequently asked
My cat's hematocrit is 30 percent. Is that anemia?
Usually not on its own, since the feline interval runs about 24 to 45 percent. A value of 30 percent matters when it has fallen from 38 percent over 6 months, or when total protein is low or reticulocytes are not rising, so ask for the previous results before treating the number as disease.
Why is a low white cell count more worrying than a high one in cats?
Because cats do not store large marrow reserves of neutrophils. A count under 5.5 x 10^9/L can reflect panleukopenia, FeLV or FIV related suppression, or sepsis with consumption, and a neutropenic cat with fever is often hospitalized rather than sent home for a recheck in a week.
Do I need a reticulocyte count with every CBC?
Only when the hematocrit is low, but then it is essential. In cats only the aggregate reticulocyte count signals recent regeneration, and it separates blood loss or hemolysis from the non-regenerative pattern of kidney disease, chronic inflammation or marrow disease.