The CBC Blood Test for Dogs Explained

The CBC blood test for dogs, also called a complete blood count, checks the number and types of blood cells present in the dog. This test is important when diagnosing illnesses.

Red Blood Cells

A function of the CBC test is to evaluate the red blood cells. When the red blood cell count is abnormal, it is indicative of certain problems. In a CBC blood test, the method in which the red blood cell count is determined is called a hematocrit, or packed cell volume. If the hematocrit is low, that means there aren’t enough red blood cells in the body and the dog is anemic. If the count is high, there are too many red blood cells. This is usually the case in dogs who are dehydrated, in shock, have diseases of lungs or who are in higher altitudes.

White Blood Cells

The CBC blood test also monitors the amount of white blood cells present. White blood cells, also called leukocytes, help to defend the body against bacteria, viruses and fungi. If a dog has an elevated white blood cell count, it could mean that there is an infection in the body or it is stressed by metabolic toxins. There are five different types of leukocytes—neutrophils, eosinophils, basophils, lymphocytes and monocytes— and each helps the body in its own way. If the values of one type of leukocyte are elevated, it can help the doctor determine what kind of problem is going on in the dog.

Neutrophils help to defend the body against bacterial infections. The cells will actually engulf bacteria and other materials to keep them from causing problems. An elevated neutrophil count is usually indicative of a bacterial infection or some extreme form of stress.

Elevated eosinophils are seen when an animal is suffering from a parasitic infection or allergies. Like neutrophils, eosinophils also have the ability to engulf foreign materials in the body.

Basophils are a type of white blood cell whose function is unknown. Basophils are created in the bone marrow and are not present in many CBC blood tests.

Lymphocytes are typically abundant in the blood and are divided into two major types—B cells and T cells. B cells help to fight off invading organisms by producing antibodies. T cells help other cells destroy viruses and other foreign matter that enters the body. An increased lymphocyte count is usually present when an animal has a prolonged illness, such as a bacterial or viral infection that has occurred for a long period of time, or if the dog has certain auto-immune diseases, such as leukemia.

Monocytes are used to defend the body against infectious organisms by engulfing the invaders. They also help to cure inflamed and irritated tissue by secreting protein molecules.


Platelets are another component that is checked in the CBC blood test. Platelets assist in clot formation. If this count is low, it could mean that a large amount have been used when trying to heal a cut that is within the body, or that the number is actually low and the dog is in danger of bleeding to death.