Blood tests are important for monitoring your health. If you have unexplained inflammation, infections, or bleeding, a complete blood count (CBC) can help diagnose any conditions that you may have. Keep reading to learn more about CBC tests.

What is a Complete Blood Count (CBC) Test?

A complete blood count (CBC) is a type of blood test that evaluates blood cells. It gives you information about the following types of cells found in the blood: white blood cells (WBCs), red blood cells (RBCs), and platelets. CBC tests are also known as full blood count or full blood exams [1].

Why is This Test Done?

The CBC is a common test and is normally performed during a routine health exam [2].

When a patient has unexplained symptoms and inflammation, doctors can order a CBC test to diagnose the condition. CBC tests can help detect anemia, infections, clotting problems, immune system disorders, and blood cancers [1].

They are also used to monitor a patient’s existing condition or the effectiveness of a certain treatment. For example, chemotherapy may affect a person’s blood count. A CBC test can be used to determine whether or not the treatment negatively affects the patient’s blood cell count [3, 4].

What is Tested in the CBC?

A CBC test usually includes the following:

  • WBC count
  • WBC differential
  • RBC count
  • Hemoglobin
  • Hematocrit
  • RBC indices
    • Mean corpuscular volume (MCV)
    • Mean corpuscular hemoglobin (MCH)
    • Mean corpuscular hemoglobin concentration (MCHC)
    • Red cell distribution width (RDW)
  • Reticulocyte count
  • Platelet count
    • Mean platelet volume (MPV)

White Blood Cell (WBC) Count

This test measures the total number of white blood cells (WBCs, or leukocytes) in the blood. They help fight bacteria, viruses, and other foreign invaders, thus protecting us against infections and diseases.

Having low WBC levels can mean that your body doesn’t have adequate resources to fight against infections properly. High WBC may mean that you’re currently fighting on an infection. However, high WBC levels can also be bad. White blood cells are inflammation markers, and high WBC levels can indicate chronic inflammation in your body.

Elevated WBC levels may also increase the risk of type II diabetes and reduced insulin resistance [5].

White Blood Cell (WBC) Differential

Having a normal percentage of each different type of WBC is also important for your health. If your white blood cells are increased or decreased, it is important to see which particular cells are the cause [6].

This test identifies and counts the number of particular WBCs. The different types of white blood cells include:

  • Neutrophils, which help fight infection by ingesting microbes and releasing enzymes that kill them.
  • Lymphocytes, which produce antibodies and kill cancer and virus-infected cells.
  • Monocytes, which engulf and destroy foreign material.
  • Eosinophils, which fight parasite infections and are involved in the allergic response.
  • Basophils, which are involved in the inflammatory response.

Red Blood Cell (RBC) Count

This test measures the number of red blood cells (RBCs) in your blood. The main function of these cells is supplying oxygen to your tissues.

A low red blood cell count means that you have anemia, and the ability to transport oxygen to your body’s tissues is impaired. Low RBC can be due to bleeding, injuries, malnutrition and particular nutrient deficiencies, liver, kidney, or bone marrow disorders [7].

A high RBC means that your body is trying to compensate for the lack of oxygen, which can be due to various causes. Some include high altitude, smoking, lung, heart, kidney, or bone marrow disorders.

Red Blood Cell Indices

These tests provide information about red blood cells’ physical characteristics.

  • Red blood cell distribution width (RDW) measures how much your red blood cells vary in size/volume. Since normal red blood cells are a standard size, a high RDW can indicate anemia, thalassemia, liver, or kidney disease.
  • Mean corpuscular volume (MCV) measures the average size (volume) of the red blood cells in your body. It can help distinguish between nutritional deficiencies. For example, a high MCV can indicate folate and vitamin B12 deficiency, while a low MCV indicates iron and/or copper deficiency.
  • Mean corpuscular hemoglobin (MCH) measures the average amount of hemoglobin in your red blood cells. Similarly to MCV, a high MCH can be due to folate/vitamin B12 deficiency, while a low MCH is most commonly due to iron deficiency anemia.
  • Mean corpuscular hemoglobin concentration (MCHC) measures the average amount of hemoglobin per red blood cells. In other words, it tells you what percentage of your blood cells are made up of hemoglobin. High levels can mean you have increased rupture or destruction of red blood cells (hemolytic anemia), while low levels usually point to iron deficiency.

Reticulocyte Count

This test measures the amount of reticulocytes in your blood. Reticulocytes are newly formed and immature red blood cells. They are formed in the bone marrow. Normally, a reticulocyte test is used to look at bone marrow function [8, 9].


This test measures the amount of hemoglobin in your blood. Hemoglobin is a protein in red blood cells that transports oxygen from the lungs to the rest of the body. After the oxygen is used, hemoglobin carries the released carbon dioxide back to the lungs, where it is exhaled [10].

Hemoglobin levels are used to diagnose anemia and polycythemia (increased production of red blood cells). Both low and high hemoglobin levels are bad. They both decrease the tissue oxygen supply, although by different mechanisms. High hemoglobin further increases oxidative stress and inflammation, and the risk of high blood pressure, metabolic syndrome, and blood clots [11, 12, 13, 14, 15, 16].


This test measures the percentage of your total blood is made of red blood cells (by volume). Because red blood cells carry oxygen from the lungs to the rest of the body, hematocrit is an indicator of how well the body is able to deliver oxygen to tissues [17].

Hematocrit can be high if you are dehydrated, overweight, smoking, or drinking alcohol. It is also elevated in a wide range of other medical conditions. High levels of hematocrit increase the risk of blood clots, stroke, and heart disease [18, 19, 20].

Low hematocrit can be due to anemia, thalassemia, or other diseases and disorders.

Platelet Count

This test measures the number of platelets you have in your blood. A platelet, also called thrombocyte, is a type of cell that helps the blood to clot. Clotting helps slow down or stop bleeding and heal wounds.

Not enough platelets can cause problems with blood clotting, which can cause excessive bleeding and prevent wounds from healing properly. Platelets may be low either because not enough are being made or too many are being destroyed. This can be due to medications, or underlying diseases, such as lupus or leukemia [21].

Platelet levels are elevated in infections and inflammatory disorders.

Mean Platelet Volume (MPV)

This test measures the average size of the platelets found in your blood [22].

Platelet size is larger when the body is producing an increased amount of platelets, so an MPV test can be used to assess problems with platelet production in the bone marrow or platelet destruction [23].

Irregular CBC Results?

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