To determine your general health status; to screen for, diagnose, or monitor any one of a variety of diseases and conditions that affect blood cells, such as anemia, infection, inflammation, bleeding disorder or cancer
Complete Blood Count (CBC)
As part of a routine medical exam; when you have signs and symptoms that may be related to a condition that affects blood cells; at regular intervals to monitor treatment or disease status or when you are receiving treatment known to affect blood cells
A blood sample drawn from a vein in your arm or a fingerstick or heelstick (newborns)
None
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How is the test used?
The complete blood count (CBC) is often used as a broad screening test to determine your general health status. A CBC may be used to:
- Screen for a wide range of conditions and diseases
- Help diagnose various diseases and conditions, such as anemia, infection, inflammation, bleeding disorder or leukemia, to name just a few
- Monitor the status of a disease or condition and the effectiveness of treatment after a diagnosis is established
- Monitor treatment that is known to adversely affect blood cells, such as chemotherapy or radiation therapy
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When is it ordered?
The CBC is a very common test. You may have a CBC performed when you have a routine health examination.
A CBC may be ordered when you are ill and/or have signs and symptoms that may be related to conditions that affect blood cells. The test may be ordered when you have fatigue or weakness, or easy bruising or bleeding, or when you have signs and symptoms suggesting an infection or inflammation, to name a few examples.
When you have been diagnosed with a disease known to affect blood cells, a CBC will often be ordered on a regular basis to monitor the status of your disease/condition. Likewise, if you are being treated for a blood-related disorder, then a CBC may be performed frequently to determine if the treatment is effective.
Some therapies, such as chemotherapy, can affect bone marrow production of cells. Some medications can decrease WBC counts overall. A CBC may be ordered on a regular basis to monitor these drug treatments.
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What does the test result mean?
A healthcare practitioner typically evaluates and interprets results from the components of the CBC together. Depending on the purpose of the test, a number of additional or follow-up tests may be ordered for further investigation.
For additional details, see the tables in the section Details on CBC Results below that briefly and generally explain what the result for each component of the CBC may mean.
To see an example of a CBC lab report, see this sample report.
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My CBC report includes a result for immature granulocytes (IG). What are they?
Some automated hematology analyzers report the total number of immature granulocytes (IG) present in your blood sample. Immature granulocytes are white blood cells that have not fully developed before being released from the bone marrow into the blood. They may include metamyelocytes, myelocytes, and promyelocytes. These cells are normally only present in the bone marrow because they are precursors of neutrophils, the predominant type of white cells in blood. The presence of immature granulocytes in the blood may occur in various diseases, such as infection or a blood cancer, and thus will often prompt further investigation, which may include additional laboratory testing.
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My CBC report includes a result for immature platelet fraction (IPF). What is it?
IPF is the relative number of newly released young platelets (also called reticulated platelets) in the blood. Platelets are produced in the bone marrow and are normally not released into the bloodstream until they have matured. When platelet numbers in the blood are low (thrombocytopenia), it stimulates the bone marrow to produce platelets faster. When the need is great and when production cannot keep up with "demand," then an increased number of young platelets will be present in the bloodstream.
This IPF test result would be one of the values reported when blood is evaluated using an automated hematology analyzer. The IPF may be used to help a healthcare provider determine the likely cause of your thrombocytopenia:
- A low IPF suggests a decrease in platelet production by the bone marrow.
- A high IPF suggests an increased loss of platelets in peripheral blood.
Lab test results including platelet count and IPF can also help determine if you need a platelet transfusion and help monitor bone marrow recovery, such as after a bone marrow transplant. Other uses are being studied and the test's ultimate clinical utility has not yet been well determined.
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My CBC report includes a result for reticulocyte hemoglobin. What is it?
The hemoglobin inside of reticulocytes can be measured and reported as either a mean reticulocyte hemoglobin content (CHr) or a reticulocyte hemoglobin equivalent (Ret-He), depending upon the test method used. This test result would be one of the values reported when blood is evaluated using an automated hematology analyzer.
Reticulocytes are "young" red blood cells that are released by the bone marrow. They exist in blood for only 1-2 days before becoming fully mature. The amount of hemoglobin inside of reticulocytes can help determine your body's iron status, particularly the availability of iron to be incorporated into hemoglobin in developing red blood cells in the bone marrow, within the past few days. This makes the test useful in identifying functional iron deficiency in certain clinical conditions (e.g., after treatment with erythropoietin) and in assessing iron deficiency anemia in children.
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What diseases can a CBC detect?
A CBC can help detect a number of conditions. Some examples include:
- Anemia of various etiologies
- Autoimmune disorders
- Bone marrow disorders
- Dehydration
- Infections
- Inflammation
- Hemoglobin abnormalities
- Leukemia
- Low platelets
- Lymphoma
- Myeloproliferative neoplasms
- Myelodysplastic syndrome
- Sickle cell disease
- Thalassemia
- Nutritional deficiencies (e.g., Iron, B12 or folate)
- Cancer that has spread to the bone marrow
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If I have an abnormal result on my CBC, what other tests might my healthcare practitioner order as follow up?
It depends on the results that are abnormal and the suspected disease or condition as well as your medical history and findings from your physical examination. Your healthcare provider may request that a blood smear examination be done. Other general tests to check your health and to look for possible causes may include a comprehensive metabolic panel (CMP). A few other general examples include:
- Abnormal WBC results may be followed by tests for a suspected infection. Some examples include a culture of the affected area (e.g., blood culture, urine culture, sputum culture), a strep test or tests for viruses such as mononucleosis or EBV. If inflammation is suspected, then a CRP or ESR test may be done.
- Abnormal RBC results may prompt a reticulocyte count, iron studies, tests for vitamin B12 and folate, G6PD, or hemoglobinopathy evaluation to help make a diagnosis.
- An abnormal platelet count may be followed by tests that further evaluate platelets, such as HIT antibody. Additional tests may be done to check for bleeding disorders or excessive clotting disorders such as PT, PTT, von Willebrand factor or coagulation factors.
When a serious condition such as leukemia, lymphoma, myelodysplasia or another bone marrow disorder is suspected, then a bone marrow aspiration and biopsy may be necessary. Numerous other tests specific for certain conditions may be needed to establish a diagnosis, such as flow cytometry, chromosome analysis, and/or gene mutation analysis. Talk to your healthcare provider about the results of your CBC, whether additional tests are necessary, and why.
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Is there anything else I should know?
Many different conditions can result in increases or decreases in blood cell populations. Some of these conditions may require treatment, while others may resolve on their own.
Recent blood transfusions affect the results of the CBC.
Normal reference CBC values for babies and children are different from adults. The laboratory will supply the reference intervals for various age groups, and a healthcare practitioner will take these into consideration when interpreting data.
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Red Blood Cell (RBC) Tests
For detailed information on each test component, click on the name of the component to go to the specific article.
To see an example of a CBC lab report, see this sample report.
Note: The reference ranges provided here represent a theoretical guideline that should not be used to interpret your test results. Some variation is likely between these numbers and the reference range reported by the lab that ran your test. Please consult your doctor. For more information on reference ranges, please read Reference Ranges and What They Mean.
Reference ranges listed here are for adults older than 18 years old. They are not available for youths 0-18 years old due to wide variability. See the child's lab report for reference ranges.
Conventional Units are typically used for reporting results in U.S. labs. SI Units are used to report lab results outside of the U.S.
TEST Reference Range2 Examples of causes of low result Examples of causes of high result Red Blood Cell Count
(RBC)Conventional Units
Men: 4.5-5.9 x 106/microliter
Women: 4.1-5.1 x 106 microliter
SI Units
Men: 4.5-5.9 x 1012/L
Women: 4.1-5.1 x 1012/L
Known as anemia - Acute or chronic bleeding
- RBC destruction (e.g., hemolytic anemia, etc.)
- Nutritional deficiency (e.g., iron deficiency, vitamin B12 or folate deficiency)
- Bone marrow disorders or damage
- Chronic inflammatory disease
- Chronic kidney disease
Known as polycythemia - Dehydration
- Lung (pulmonary) disease
- Kidney or other tumor that produces excess erythropoietin
- Smoking
- Living at high altitude
- Genetic causes (altered oxygen sensing, abnormality in hemoglobin oxygen release)
- Polycythemia vera—a rare disease
(Hb)
Conventional Units
Men: 14-17.5 g/dL
Women: 12.3-15.3 g/dL
SI Units
Men: 140-175 g/L
Women: 123-153 g/L
Usually mirrors RBC results, provides added information Usually mirrors RBC results (Hct)
Conventional Units
Men: 41.5-50.4%
Women: 35.9-44.6%
SI Units
Men: 0.415-0.504 volume fraction
Women: 0.359-0.446 volume fraction
Usually mirrors RBC results Usually mirrors RBC results; most common cause is dehydration RBC indices MCV Conventional Units
80-96 micrometer3
SI Units
80-96 fL
Indicates RBCs are smaller than normal (microcytic); caused by iron deficiency anemia or thalassemias, for example. Indicates RBCs are larger than normal (macrocytic), for example in anemia caused by vitamin B12 or folate deficiency, myelodysplasia, liver disease, hypothyroidism, etc. MCH Conventional Units
27.5-33.2 pg
SI Units
27.5-33.2 pg
Mirrors MCV results; small red cells would have a lower value. Mirrors MCV results; macrocytic RBCs are large so tend to have a higher MCH. MCHC Conventional Units
33.4-35.5 g/dL
SI Units
334-355 g/L
May be low when MCV is low; decreased MCHC values (hypochromia) are seen in conditions such as iron deficiency anemia and thalassemia. Increased MCHC values (hyperchromia) are seen in conditions where the hemoglobin is more concentrated inside the red cells, such as autoimmune hemolytic anemia, in burn patients, and hereditary spherocytosis, a rare congenital disorder. RBC Distribution Width (RDW, RDW-SD, RDW-CV)
Not always reported
Indicates that RBC are uniform in size. Indicates mixed population of small and large RBCs; young RBCs tend to be larger. For example, in iron deficiency anemia or pernicious anemia, there is high variation (anisocytosis) in RBC size (along with variation in shape – poikilocytosis), causing an increase in the RDW. Not always done
Conventional Units
0.5-1.5% or
25-125 x 103/microliterSI Units
0.005-0.015 number fraction or
25-125 x 109/LIn the setting of anemia, a low reticulocyte count indicates a condition is affecting the production of red blood cells, such as bone marrow disorder or damage, or a nutritional deficiency (iron, B12 or folate). In the setting of anemia, a high reticulocyte count generally indicates peripheral cause, such as bleeding or hemolysis, or response to treatment (e.g., iron supplementation for iron deficiency anemia). 1 from Wintrobe's Clinical Hematology. 14th ed. Greer J, editor. Philadelphia, PA: Wolters Kluwer: 2019.
2 from Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. McPherson R, Pincus M, eds. Philadelphia, PA: Elsevier Saunders; 2011.
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White Blood Cell (WBC) Tests
For detailed information on each test component, click on the name of the component to go to the specific article.
To see an example of a CBC lab report, see this sample report.
Note: The reference ranges provided here represent a theoretical guideline that should not be used to interpret your test results. Some variation is likely between these numbers and the reference range reported by the lab that ran your test. Please consult your doctor. For more information on reference ranges, please read Reference Ranges and What They Mean.
Reference ranges listed here are for adults older than 18 years old. They are not available for youths 0-18 years old due to wide variability. See the child's lab report for reference ranges.
Conventional Units are typically used for reporting results in U.S. labs. SI Units are used to report lab results outside of the U.S.
Test Reference Range2 Examples of causes of a low count Examples of causes of a high count (WBC)
Conventional Units1
4,500-11,000 white blood cells per microliter (mcL)
SI Units1
4.5-11.0 x 109 per liter (L)
Known as leukopenia - Bone marrow disorders or damage
- Autoimmune conditions
- Severe infections (sepsis)
- Lymphoma or other cancer that spread to the bone marrow
- Dietary deficiencies
- Diseases of immune system (e.g., HIV/AIDS)
Known as leukocytosis - Infection, most commonly bacterial or viral
- Inflammation
- Leukemia, myeloproliferative neoplasms
- Allergies, asthma
- Tissue death (trauma, burns, heart attack)
- Intense exercise or severe stress
(Diff)
(Not always performed; may be done as part of or in follow up to CBC)
Absolute neutrophil count, % neutrophils
(Neu, PMN, polys)
Conventional Units
Percent (mean): 56%
Absolute count (per microliter):
1800-7800SI Units
Mean number fraction: 0.56
Absolute count X 109 per liter:
1.8-7.8Known as neutropenia - Severe, overwhelming infection (sepsis)
- Autoimmune disorders
- Dietary deficiencies
- Reaction to drugs
- Immunodeficiency
- Myelodysplasia
- Bone marrow damage (e.g., chemotherapy, radiation therapy)
- Cancer that spreads to the bone marrow
- Congenital neutropenia
Known as neutrophilia - Acute bacterial infections
- Inflammation
- Trauma, heart attack, or burns
- Stress, rigorous exercise
- Certain leukemias (e.g., chronic myeloid leukemia)
- Cushing syndrome
Absolute lymphocyte count, % lymphocytes
(Lymph)
Conventional Units
Percent (mean) 34%
Absolute count (per microliter):
1000-4800SI Units
Mean number fraction: 0.34
Absolute count X 109 per liter:
1.0-4.8Known as lymphocytopenia - Autoimmune disorders (e.g., lupus, rheumatoid arthritis)
- Infections (e.g., HIV, viral hepatitis, typhoid fever, influenza, Covid-19)
- Bone marrow damage (e.g., chemotherapy, radiation therapy)
- Corticosteroids
Known as lymphocytosis - Acute viral infections (e.g., chicken pox, cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes, rubella)
- Certain bacterial infections (e.g., pertussis (whooping cough), tuberculosis (TB))
- Toxoplasmosis
- Chronic inflammatory disorder (e.g., ulcerative colitis)
- Lymphocytic leukemia, lymphoma
- Stress (acute)
Absolute monocyte count, % monocytes
(Mono)Conventional Units
Percent (mean) 4%
Absolute count (per microliter)
0-800SI Units
Mean number fraction 0.04
Absolute count X 109 per liter
0-0.80Usually, one low count is not medically significant. Repeated low counts can indicate:
- Bone marrow damage or failure
- Hairy cell leukemia
- Aplastic anemia
- Chronic infections (e.g., tuberculosis, fungal infection)
- Infection within the heart (bacterial endocarditis)
- Collagen vascular diseases (e.g., lupus, scleroderma, rheumatoid arthritis, vasculitis)
- Monocytic or myelomonocytic leukemia (acute or chronic)
Absolute eosinophil count, % eosinophils
(Eos)
Conventional Units
Percent (mean) 2.7%
Absolute count (per microliter)
0-450SI Units
Mean number fraction 0.027
Absolute count X 109 per liter
0-0.45Numbers are normally low in the blood. One or an occasional low number is usually not medically significant. - Asthma, allergies such as hay fever
- Drug reactions
- Parasitic infections
- Inflammatory disorders (celiac disease, inflammatory bowel disease)
- Some cancers, certain acute or chronic leukemias or lymphomas
- Addison disease
- Connective tissue disorders
Absolute basophil count, % basophils
(Baso)
Conventional Units
Percent (mean) 0.3%
Absolute count (per microliter)
0-200SI Units
Mean number fraction 0.030
Absolute count X 109 per liter
0-0.20As with eosinophils, numbers are normally low in the blood; usually not medically significant - Rare allergic reactions (hives, food allergy)
- Inflammation (rheumatoid arthritis, ulcerative colitis)
- Some leukemias
- Uremia
1 from Wintrobe's Clinical Hematology. 14th ed. Greer J, editor. Philadelphia, PA: Wolters Kluwer: 2019.
2 from Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. McPherson R, Pincus M, eds. Philadelphia, PA: Elsevier Saunders; 2011.
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Platelet Tests
For detailed information on each test component, click on the name of the component to go to the specific article.
To see an example of a CBC lab report, see this sample report.
Note: The reference ranges provided here represent a theoretical guideline that should not be used to interpret your test results. Some variation is likely between these numbers and the reference range reported by the lab that ran your test. Please consult your doctor. For more information on reference ranges, please read Reference Ranges and What They Mean.
Reference ranges listed here are for adults older than 18 years old. They are not available for youths 0-18 years old due to wide variability. See the child's lab report for reference ranges.
Conventional Units are typically used for reporting results in U.S. labs. SI Units are used to report lab results outside of the U.S.
Test Reference Range2 Examples of causes of low result Examples of causes of high result (Plt)
Conventional Units
150-450 x 103/microliter
SI Units
150-450 x 109/L
Known as thrombocytopenia: - Viral infection (mononucleosis, measles, hepatitis)
- Rocky mountain spotted fever
- Platelet autoantibody
- Drugs (acetaminophen, quinidine, sulfa drugs)
- Cirrhosis
- Autoimmune disorders (e.g., ITP)
- Sepsis
- Leukemia, lymphoma
- Myelodysplasia
- Chemo or radiation therapy
Known as thrombocytosis: - Cancer (lung, gastrointestinal, breast, ovarian, lymphoma)
- Rheumatoid arthritis, inflammatory bowel disease, lupus
- Iron deficiency anemia
- Hemolytic anemia
- Myeloproliferative disorder (e.g., essential thrombocythemia)
(Not always reported)
Mean Platelet Volume Indicates average size of platelets is small; older platelets are generally smaller than young ones and a low MPV may mean that a condition is affecting the production of platelets by the bone marrow. Indicates a high number of larger, younger platelets in the blood; this may be due to the bone marrow producing and releasing platelets rapidly into circulation. (Not always reported)
Platelet Distribution Width Indicates uniformity in size of platelets. Indicates increased variation in the size of the platelets, which may mean that a condition is present that is affecting platelets. 1 from Wintrobe's Clinical Hematology. 14th ed. Greer J, editor. Philadelphia, PA: Wolters Kluwer: 2019.
2 from Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. McPherson R, Pincus M, eds. Philadelphia, PA: Elsevier Saunders; 2011.




