Elevated Neutrophils & Eosinophils in Cats

Scoring average on my differential doesn't mean I's an average cat.
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It's not unusual to have some trepidation about blood tests, even if Kitty's getting them and not you. Blood tests measure neutrophils, eosinophils, lymphocytes, hematocrit and more. Results can be confusing and intimidating. Elevated neutrophil and eosinophil levels in your cat could indicate a variety of things.

The CBC and the Differential

To have a good understanding of Kitty's blood work, it's important to understand the basics. Vets routinely run a complete blood count, commonly called the CBC, to gather information about a cat who's not feeling well or to gather baseline information about an older cat. The CBC is often part of routine wellness exams. The CBC does more than count blood cells; it measures platelets, which determine clotting ability, as well as a variety of other data about Kitty's condition. The differential, which is part of the CBC, analyzes the varying types of white blood cells; the distribution of these cells is a valuable tool in helping to determine what's causing Kitty's illness.


Most of the white blood cells in Kitty's blood stream are neutrophils, which are the first to respond to an infection. Because of their fast response, a high neutrophil count is present in a variety of conditions, such as cancer and inflammation. Mature neutrophils are known as segs, and immature ones are known as bands. If Kitty has a bacterial infection, more bands are released to fight it; the higher the concentration of bands in her blood count the more severe the infection is. Occasionally an infection or inflammation will be so severe that the body can't keep up with the demand for neutrophils, which can actually result in a low neutrophil count.


Eosinophils are white blood cells produced in marrow, which migrate into tissues after circulating in Kitty's blood for a few hours. The most common cause of high numbers of eosinophils is usually parasites, such as heartworms, and hypersensitivity and allergic reactions. Some tumors and cancers, such as mast cell tumors and lymphoma, will present an elevated eosinophil count, known as eosinophilia. A number of conditions are associated with eosinophilia, so cancer is only one of a variety of conditions that your vet will consider when he looks at the results of the CBC and the differential.

Elevated Neutrophils and Eosinophils

If Kitty has an elevated neutrophils and eosinophils count, there's no way to definitively state that she has a certain disease without understanding what else is going on in her body. The vet will examine her symptoms and the CBC as a whole to determine a cause for her illness and determine a course of treatment. As well, your vet may have to perform more diagnostic tests. High levels of neutrophils and eosinophils may indicate a variety of conditions, including inflammatory bowel disease and some cancers, that require a big-picture analysis to differentiate.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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