Why Is My Dog Or Cat's Monocyte Count High ?













Ron Hines DVM PhD

To see what normal blood and urine values are, go here

For an explanation of causes of most abnormal blood and urine tests, go here

To see how tests are grouped, go here

Monocytes In Your Pet's Blood = Monos

When your veterinarian orders a CBC/WBC (complete blood cell count) for your pet, monocytes will be one of the cell types listed in the results. Monocytes are cells that is quite variable in size and appearance (pleomorphic) . They are a bit larger than neutrophils, lymphocytes and eosinophils – the more common white blood cells listed in the CBC/WBC.

Monocytes are manufactured in your pet’s bone marrow, after which they circulate in your dog or cat's blood briefly. They then take up residence in tissues throughout its body as macrophage and dendritic – cells whose job it is to engulf (eat, "vacuum cleaner" effect) undesirable things that pass their way or present suspicious organic substances, bacteria and virus to other immune cells (T-cells). The T cells then make decisions as to whether those substances need to be cleansed from the body, destroyed or ignored. Within the last few years, it has become apparent that resident monocytes (ie macrophages) have other important duties that do not involve your pet's immune system. Things as amazing as maintaining proper body temperature and regulating heartbeat. (ref)



Persistently high monocyte numbers only confirm the obvious, that your pet is quite ill and has been for some time. The lab or your veterinarian might see phagocytized (engulfed) bacteria within the monocytes.

Some Reasons Why Your Pet’s Monocyte Count Might Be High (Monocytosis) :

All chronic infectious and non-infectious diseases that produce inflammation can increase monocyte numbers in your pet. Stress or a trip to the veterinary office (in dogs), corticosteroid administration (in dogs) can also cause monocyte numbers to rise briefly.

On very rare occasions, leukemia of the monocyte cell line (monocytic leukemia) can elevate blood monocyte numbers can account for high monocyte numbers.

Some Reasons Your Pet’s Monocyte Count Could be Low Or Absent :

Less than normal, or no monocytes (monocytopenia) are occasionally found in blood samples. When that occurs, it does not appear to relate to any disease or health issue.