A complete blood count (CBC) is a blood test that measures amounts and sizes of your red blood cells, hemoglobin, white blood cells and platelets. A provider can use it to monitor and diagnose medical conditions and check on the health of your immune system. Infections, medications, anemia and cancer can cause abnormal results.
A complete blood count (CBC) is a blood test that providers use to monitor or diagnose health conditions. It can give your provider information about how medications or medical conditions are affecting your body, and about the health of your immune system. It can detect blood cancers, anemia, infections and other conditions.
For a CBC blood test, a healthcare provider takes a sample of your blood and sends it to a lab. The lab measures the amount of red blood cells, hemoglobin (the protein that carries oxygen in your red blood cells), white blood cells and platelets. They also measure the size of your blood cells. Along with a CBC, your provider might order a peripheral blood smear, which gives them more information about how your blood cells look under a microscope.
A CBC with differential means that the lab also counts each different type of white blood cell and immature (not-yet-fully-developed) blood cells. This gives your provider more information about what’s happening with different immune system cells.
Your provider might order a CBC test:
A CBC test can tell your provider if you have:
These can be signs of many health conditions, including infections, cancer, blood conditions and medication side effects. But your provider can use the results of your CBC, along with your symptoms, to narrow down or diagnose the cause.
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During a CBC test, a special computer counts and looks at the size of red blood cells (erythrocytes), white blood cells (leukocytes) and platelets (thrombocytes). If your provider orders a CBC with differential, it also counts the different types of white blood cells and immature cells in your sample. If there’s anything unclear about your results, a pathologist will look at your sample under a microscope to verify the computer’s results.
In a CBC for red blood cells, your providers look at:
You might also see indices, which describe the size of your red blood cells and hemoglobin concentrations. These include:
The results of your platelet count on a CBC include:
Your provider can order a CBC with just total white blood cell counts or with a differential. A differential counts each different type of white blood cell and immature red blood cells. These might be shown as an absolute number of cells (written as “abs”) or a percentage (%) of all of your white blood cells.
You might see on your CBC report:
You don’t need to fast or follow special instructions to prepare for a CBC. You can eat, drink and take your medications as you normally would. But if your provider is taking samples for other blood tests at the same time, you may have special instructions for those tests.
To get a blood sample, your provider cleans your arm and inserts a needle. The needle may sting or pinch a little. In infants, providers usually insert the needle into the baby’s heel.
Through the needle, your provider removes a sample of your blood and collects it in a tube. Sometimes, your provider takes more than one tube of blood.
After drawing blood, your provider removes the needle and places a bandage on your arm. Your provider sends the blood to a lab for testing.
After a blood draw for a CBC test, you’ll have some gauze and a bandage on your arm, secured with tape. Your arm may be a little sore for a few hours. You may develop a small bruise where your provider inserted the needle.
A CBC is a safe, common test. There’s a small risk of infection at the site of the blood draw, especially if you have a weakened immune system. Rarely, some people feel a little faint or lightheaded after a blood draw.
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Normal ranges for values on your complete blood count can vary some, but in general, they include:
Test | Normal value for adults |
---|---|
WBC | 4,000 to 10,000 cells per mcL (4.0 to 10 k/mcL) |
RBC | 4.0 to 5.4 million cells per mcL (for people assigned female at birth/AFAB or taking estrogen) or 4.5 to 6.1 million cells per mcL (for people assigned male at birth/AMAB or taking testosterone) |
Hb | 11.5 to 15.5 g/dL (for people AFAB or taking estrogen) or 13 to 17 g/dL (for people AMAB or taking testosterone) |
Hct | 36% to 48% (for people AFAB or taking estrogen) or 40% to 55% (for people AMAB or taking testosterone) |
MCV | 80 to 100 fL (femtoliters) |
MCH | 27 to 31 pg (picograms) per cell |
MCHC | 32 to 36 g/dL (grams per deciliter) |
RDW | 12% to 15% |
Platelet count | 150,000 to 400,000 cells per mcL (150 to 400 k/mcL) |
MPV | 7.0 fL to 9.0 fL |
Neutrophils | 2,500 to 7,000 per mcL (2.5 to 7.0 k/mcL) |
Lymphocytes | 1,000 to 4,800 per mcL (1.0 to 4.8 k/mcL) |
Monocytes | 200 to 800 per mcL (0.2 to 0.8 k/mcL) |
Eosinophils | Less than 500 per mcL (0.5 k/mcL) |
Basophils | Less than 300 per mcL (0.3 k/mcL) |
Immature granulocytes | Less than 100 mcL (0.1 k/mcL) |
NRBC | Less than 10 mcL (0.01 k/mcL) |
Test | |
WBC | |
Normal value for adults | |
4,000 to 10,000 cells per mcL (4.0 to 10 k/mcL) | |
RBC | |
Normal value for adults | |
4.0 to 5.4 million cells per mcL (for people assigned female at birth/AFAB or taking estrogen) or 4.5 to 6.1 million cells per mcL (for people assigned male at birth/AMAB or taking testosterone) | |
Hb | |
Normal value for adults | |
11.5 to 15.5 g/dL (for people AFAB or taking estrogen) or 13 to 17 g/dL (for people AMAB or taking testosterone) | |
Hct | |
Normal value for adults | |
36% to 48% (for people AFAB or taking estrogen) or 40% to 55% (for people AMAB or taking testosterone) | |
MCV | |
Normal value for adults | |
80 to 100 fL (femtoliters) | |
MCH | |
Normal value for adults | |
27 to 31 pg (picograms) per cell | |
MCHC | |
Normal value for adults | |
32 to 36 g/dL (grams per deciliter) | |
RDW | |
Normal value for adults | |
12% to 15% | |
Platelet count | |
Normal value for adults | |
150,000 to 400,000 cells per mcL (150 to 400 k/mcL) | |
MPV | |
Normal value for adults | |
7.0 fL to 9.0 fL | |
Neutrophils | |
Normal value for adults | |
2,500 to 7,000 per mcL (2.5 to 7.0 k/mcL) | |
Lymphocytes | |
Normal value for adults | |
1,000 to 4,800 per mcL (1.0 to 4.8 k/mcL) | |
Monocytes | |
Normal value for adults | |
200 to 800 per mcL (0.2 to 0.8 k/mcL) | |
Eosinophils | |
Normal value for adults | |
Less than 500 per mcL (0.5 k/mcL) | |
Basophils | |
Normal value for adults | |
Less than 300 per mcL (0.3 k/mcL) | |
Immature granulocytes | |
Normal value for adults | |
Less than 100 mcL (0.1 k/mcL) | |
NRBC | |
Normal value for adults | |
Less than 10 mcL (0.01 k/mcL) |
Normal ranges for a CBC blood test can vary based on:
Always be sure to check the reference range (the range of numbers considered normal) provided on your results and compare your numbers only to the reference. Ask your provider if you have any questions.
Results are usually ready within a few days. Sometimes, it only takes 24 hours to get results. Your provider will contact you to explain the results and discuss next steps.
Many health conditions can cause high or low blood counts. Some of these are serious and others are common and easily treatable. For example:
If your results are out of the reference range, talk to your provider about what they might mean. They may order follow-up tests or start a treatment plan. Or you may not need treatment, only monitoring.
Contact your provider if you have any questions about the test or the results.
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A CBC doesn’t directly show how well your kidneys are functioning. But some numbers, like lymphocytes and MCV, along with other tests, can help your provider get a better picture of how well your kidneys are working.
A note from Cleveland Clinic
A complete blood count is a common blood test that providers use to learn more about your health. You may have one as part of a routine exam or to help your provider understand the symptoms you’re having. While waiting for the results of a test might make you feel anxious, it can be helpful to remember that the results of a CBC give your provider important clues about what’s happening inside your body. These clues can help you get the right diagnosis and treatment to help you feel better.
Last reviewed on 03/14/2024.
Learn more about the Health Library and our editorial process.
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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy