Low Lymphocytes in Cats

Lymphocytes are one of the white blood cells a differential measures.
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If Tessa's recent blood tests came back revealing a low lymphocyte count, remember that her health state goes beyond one number before you switch to anxiety mode. There's a big picture to consider, including the other test values and her behavior.

Blood Tests: CBC and Differential

You'll learn a lot about your pet's current health with a blood test, whether Tessa hasn't been herself or the blood test is part of a regular exam. A complete blood test, more commonly known as the CBC, counts and compares a pet's red and white blood cells, providing clues about what's going on in her body. White blood cell counts are useful for learning about potential inflammation or infection. The differential, part of the CBC, takes the white blood cell count a step further, looking at the different kinds of white blood cells. The way a specific white blood cell responds can help pinpoint a condition. For example, the presence of basophils, quite rare in cats, can indicate heartworms.


Lymphocytes are the smallest of the white blood cells, typically developing outside the bone marrow in the lymph nodes, spleen and lymphoid tissue associated with the gut. As a rule, they only live for a few days; during their lifetimes, their main job is to produce antibodies and immune response. They work hard to keep Tessa healthy.

Low Lymphocytes: Lymphopenia

Normally, lymphocytes comprise 20 percent to 55 percent of Tessa's white blood cells. If her lymphocyte count is below the 20 percent mark, it's called lymphopenia. In most cases a low lymphocyte count is a result of corticosteroid medications, used to treat allergic reactions or as anti-inflammatories, or because the adrenal glands produce excess cortisol, as in Cushing's disease. Occasionally cats with acute infections, other lymphatic issues or those that have endured long periods of stress will have low lymphocyte counts.

Next Steps

If Tessa has a low lymphocyte count, don't panic. The vet will consider all pieces of the diagnostic puzzle, including her past and current health, her symptoms, and the other values in her CBC. Chances are, if the vet tells you her lymphocyte level is low yet doesn't seem too concerned about it, Tessa's fine. If everything else is as it should be, it's possible the stress of the blood draw and exam affected her lymphocyte level.

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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