What Is a Blood Count?

A blood count is a term used to describe the various types of cells present in a person's or animal's blood. Having this information can help a medical doctor determine what may be wrong with a patient, or at least rule out some possibilities. The main test used to do this is often called a complete blood count because it allows doctors the opportunity to look at the count of white blood cells, red blood cells, platelets, and other key factors.

In most cases, an individual's results are compared to baseline standards, typically a range, of what is considered normal. In some cases, the patient's previous tests may be compared with the current test to determine what changes have taken place, which may also help detail any progression of a disease. These counts may fall slightly outside the normal range and not be much cause for concern, but may prompt a doctor to order more tests or begin a certain treatment procedure.

One of the key factors in a blood test is the issue of white blood cells. If more are found than normally exist in a healthy individual, it could indicate white blood cells are being produced to fight an infection. A low number could indicate an immune deficiency of some sort. In both cases, the cause of the unusual white blood cell count could be reason for concern, and the doctor may need to proceed out of an abundance of caution with a plan to make a more firm diagnosis.

The red blood cells are also a concern in a blood count. A low red blood cell count means areas of the body may not be receiving enough oxygen, a condition known as anemia. In such cases, the doctor's main objective is to find the underlying cause, which could be something simple like an iron deficiency, or something more serious like leukemia.

The platelet count is also a focus of a blood count test. These form the main clotting mechanism for blood in the body. A low platelet count may signify a large amount of internal or external bleeding, depending on the situation. If internal bleeding is a concern, the blood count may prompt the doctor to run imaging tests in an attempt to find the location of the problem.

In most cases, a blood count can offer clues to an illness, but will often be only one step in the diagnostic process. Rarely do these tests actually identify the problem with any degree of certainty. Therefore, these tests must be considered along with all the other available evidence so that the proper diagnosis and course of treatment are chosen.