What is CBC?
The complete blood count (CBC) is a simple blood test to evaluate overall health and detect a wide range of disorders, such as anemia, infection, and leukemia. The complete blood count is the calculation of the cellular of blood. A CBC test measures several components and features of your blood include:
- Red blood cells: RBC delivers oxygen throughout the body. They also help in carrying carbon dioxide. If your RBC count is too low, you may have anemiaor another health issue. Red blood cells are also called erythrocytes.
RBCs are produced in the bone marrow and released into the bloodstream when they mature. The typical lifespan of an RBC is 120 days. Thus, the bone marrow must continually produce new RBCs to replace those that age and degrade or are lost through bleeding. Several conditions can affect the production of new RBCs and their lifespan, in addition to those conditions that may result in significant bleeding.
- White blood cells: WBC helps your body to fight against germs. WBCs are present in the blood at relatively stable numbers. However, these numbers may temporarily shift higher or lower depending on what is going on in the body. If you have an increased number of WBC, it could be a sign of inflammation, infection, a medical reaction, or another health condition.
If you have decreased number of WBC, then you could be at a higher risk for infection. A medication, a viral infection, or a bone marrow disease could also cause a low count. White blood cells are also called leukocytes.
- Hemoglobin (Hb or Hgb):This is the protein in your blood that holds oxygen. Abnormalities can be a sign of problems ranging from anemia to lung disease.
- Hematocrit (Hct):It tells how much of your blood is made up of red blood cells. A low hematocrit may signify that you don't have enough iron, the mineral that helps your body make red blood cells, and it cause too much bleeding. A higher than usual hematocrit can be caused by dehydration or other disorders.
- Platelets: These are tiny cell fragments that circulate in the blood and essential for normal blood clotting. When an injury and bleeding begin, platelets help stop bleeding by adhering to the injury site and clumping together to form a temporary plug.
They also release chemical signals that attract and promote the clumping of additional platelets and eventually become part of a stable blood clot at the injury site that remains in place until the injury heals. Platelets are also called thrombocytes.
- Mean corpuscular volume (MCV):MCV is the average size of your red blood cells. MCV goes up when your red blood cells are more than normal. This happens if you have anemia caused by low vitamin B-12 or folate levels. If your red blood cells are less than normal, it means you have other types of anemia, such as iron deficiency anemia.
Abnormal increases or decreases in cell counts as revealed in a complete blood count may indicate that you have an underlying medical condition that calls for further evaluation. Normal values can vary depending on your age and gender.
What is CBC Used for?
A complete blood count is a common blood test that's done for a variety of reasons, such as:
- To review your overall health:Your doctor may recommend a complete blood count as part of a routine health checkup to know about your general health and screen for any disorders.
- To diagnose disorders: Your doctor may suggest a complete blood count if you're experiencing weakness, fatigue, fever, inflammation, bruising, or bleeding. A complete blood count may help diagnose the cause of these signs and symptoms. If your doctor detects any infection, the test can also help confirm that diagnosis.
- To monitor a medical condition:If you've been diagnosed with a blood disorder that affects blood cell counts, your doctor may use complete blood counts to monitor your condition.
- To monitor treatment: A complete blood count is used to monitor your health if you're taking medications that may affect blood cell counts.
CBC Test Result
A CBC is typically performed using an automated instrument that measures various parameters, including cell counts and the physical features of some of the cells. A standard CBC includes:
1. Red blood cell (RBC) tests: Red blood cell test provides information about red blood cell count, hemoglobin, and hematocrit:
- A red blood cell count counts the actual number of red blood cells in your blood sample.
- Hemoglobinmeasures the total amount of the oxygen-carrying protein in the blood, which generally reflects the number of red blood cells in the blood.
- Hematocritmeasures the percentage of your total blood volume that consists of red blood cells.
- Mean corpuscular volume (MCV) is a measurement of the average size of your red blood cells.
- Mean corpuscular hemoglobin (MCH) calculates the average amount of hemoglobin inside your red blood cells.
- Mean corpuscular hemoglobin concentration (MCHC) calculates the average concentration of hemoglobin inside your red blood cells.
- Red cell distribution width (RDW) is a measurement of the variation in the size of your red blood cells.
- The CBC may also include reticulocyte count, which measures the absolute count or percentage of newly released young red blood cells in your blood sample.
2. White blood cell (WBC) tests: White blood cell test provides the following information:
- A white blood cell (WBC) countis a count of the total number of white blood cells in your blood sample.
- White blood cell differential measures the number of each type of white blood cell.There are five major types of white blood cells, and each type plays a different role in protecting the body.
3. Platelet tests: Platelet test provides the following information:
- The platelet count is the number of platelets in your blood sample.
- Mean platelet volume (MPV) may be reported with a CBC. It is a measurement of the average size of platelets.
- Platelet distribution width (PDW) can also report with a CBC. It reflects how uniform platelets are in size.
CBC Test Ranges and Causes
The amounts of each of these types of cells have a normal range. Your health care team will note this range on your CBC lab results. A range is used instead of a specific number because a normal amount is different for each person, as shown below:
||Cause of Low Result
||Cause of High Result
|Red blood cell count
||Male: 4.35 to 5.65 trillion cells/L*
(4.35 to 5.65 million cells/mcL**)
Female: 3.92 to 5.13 trillion cells/L
(3.92 to 5.13 million cells/mcL)
- Acute or chronic bleeding
- RBC destruction
- Nutritional deficiency
- Bone marrow disorders
- Chronic inflammatory disease
- Chronic kidney disease
- Lung disease
- Kidney or another tumor
- Living at a high altitude
- Genetic causes
- Polycythemia vera (a rare disease)
||Male: 13.2 to 16.6 grams/dL***
(132 to 166 grams/L)
Female: 11.6 to 15 grams/dL
(116 to 150 grams/L)
|Usually mirrors RBC results
||Usually mirrors RBC results
||Male: 38.3 to 48.6 percent
Female: 35.5 to 44.9 percent
|Usually mirrors RBC results
||Usually mirrors RBC results. the most common cause is dehydration
|White blood cell count
||3.4 to 9.6 billion cells/L
(3,400 to 9,600 cells/mcL)
- Bone marrow disorders
- Autoimmune conditions
- Severe infections
- Lymphoma or other cancer that spread to the bone marrow
- Dietary deficiencies
- Diseases of the immune system (e.g., HIV/AIDS)
- Infection (bacterial or viral)
- Leukemia, myeloproliferative neoplasms
- Allergies, asthma
- Tissue death (trauma, burns, heart attack)
- Intense exercise or severe stress
||Male: 135 to 317 billion/L
(135,000 to 317,000/mcL)
Female: 157 to 371 billion/L
(157,000 to 371,000/mcL)
- Viral infection (mononucleosis, measles, hepatitis)
- Rocky Mountain spotted fever
- Platelet autoantibody
- Drugs (acetaminophen, quinidine, sulfa drugs)
- Autoimmune disorders (e.g., ITP)
- Leukemia, lymphoma
- Chemo or radiation therapy
- Cancer (lung, gastrointestinal, breast, ovarian, lymphoma)
- Rheumatoid arthritis, inflammatory bowel disease, lupus
- Iron deficiency anemia
- Hemolytic anemia
- Myeloproliferative disorder
A complete blood count is not a definitive diagnostic test. If you're going for a routine checkup and have no signs or symptoms of illness but the results slightly outside the normal range, that doesn't mean serious concern.
But if you're undergoing cancer treatment, a complete blood count results outside the normal range may indicate a need to alter your treatment plan and required doctor concern.