The human body uses blood as its basic method of transporting all the important components that are required in various parts of the body. Blood flows through every part of the body, aided by the pumping action of the heart which develops the required pressure for the blood to flow. It picks up nutrition and oxygen which are sent around the body. It also collects metabolic waste and carbon dioxide from blood cells which are sent to the kidneys and lungs to be eliminated from the body. Human blood contains many different components that are essential for its proper functioning. These components are measured in a test known as a complete blood count test.

The complete blood count test is a test conducted on a sample of blood drawn from a vein in the upper forearm of the individual who is being tested. The collected blood will be examined in a laboratory for various different readings to be made. The essential components of the blood are red blood cells, white blood cells and hemoglobin. There are other tests that are conducted during the procedure such as the hematocrit and testing the mean corpuscular volume. These tests are all essential to establish the status of the basic health parameters of an individual.
The complete blood count test is conducted on nearly all patients regardless of the procedure being conducted. It is used in general health checkups as well. The components measured in a complete blood count test are noted in terms of the quantities present. These quantities are relevant to the diagnosis of many different conditions. For each patient, there is a range given for the quantity of each component.

These ranges are determined based on the age and sex of an individual. Healthy people should have their complete blood count results falling within the normal range whereas people with health problems will have variations in the readings. When diagnosing a disease or illness, there are usually symptoms that can be seen in the patients. These symptoms are often matched with complete blood count results to give a proper idea about what condition is affecting the patient. In many cases the complete blood count is conducted with a white blood cell differential which is used to measure the concentration of the different types of white blood cells. These cells include lymphocytes, basophils, eosinophils, neutrophils and monocytes. These are also diagnostically relevant.