A complete blood count (CBC) is a blood test that examines the numbers and features of blood cells. The 3 types of cells it examines are
A CBC measures the following:
- total number of red blood cells (the RBC count)
- total amount of
hemoglobin in the blood - percentage of blood made up of red blood cells (the
hematocrit ) - average red blood cell size (the mean corpuscular volume)
- average weight of hemoglobin per red blood cell (the mean corpuscular hemoglobin)
- average amount of hemoglobin per red blood cell (the mean corpuscular hemoglobin concentration)
- total number of white blood cells
- number of each type of white blood cell (the WBC differential), including
neutrophils (the absolute neutrophil count, or ANC) - number of platelets (the platelet count)
Why a CBC is done @(Model.HeadingTag)>
A CBC is a common blood test. It is often done as part of a routine checkup, but can be done at any time.
A CBC may be done to:
- learn information about your general health
- check how well the
bone marrow andspleen are working - help diagnose diseases and conditions that affect blood cells, such as
anemia , infection, blood disorders orleukemia - provide a baseline to compare with future CBCs
- check for
bone marrow suppression - monitor a condition (as a part of follow-up)
How a CBC is done @(Model.HeadingTag)>
A CBC is usually done in a community lab or hospital.
You may be given special instructions to follow before having a CBC done. Some medicines may affect CBC results, so you may be asked to stop taking certain medicines before a CBC. Check with the lab to see if you should avoid any medicines and for how long.
Blood is usually taken from a vein in the arm. An elastic band (tourniquet) is wrapped around your upper arm to apply pressure to the area and make the veins easier to see. You may be asked to make a fist so the veins stand out more. The skin is cleaned and disinfected. A needle is inserted into the vein and a small amount of blood is removed. You may feel a prick or stinging sensation.
The blood is collected in a tube and labelled with your name and other identifying information. Sometimes more than one tube of blood is collected. The tourniquet is removed and the needle is withdrawn. You may feel mild discomfort when the needle is withdrawn. Pressure is applied to the area where the needle was inserted until bleeding stops. A small bandage may be put on the area.
The blood collected is examined by a specialist in the lab (a lab technologist) using microscopes and other special equipment.
Side effects @(Model.HeadingTag)>
A CBC does not usually cause any side effects. If side effects happen, they are usually minor and happen at the needle site. Side effects that may happen include:
- discomfort
- bleeding
- bruising
- swelling
- infection
What the results mean @(Model.HeadingTag)>
CBC results are given as numbers and often depend on certain factors including sex, age and medical history. They should be compared to a normal reference range or to previous results to have meaning. Normal ranges for CBCs may vary slightly from lab to lab.
A CBC usually provides general information that can give doctors clues to possible health problems. Information from a CBC helps doctors decide whether other tests or procedures are needed to make a diagnosis. The information may also help your doctor develop or revise treatment plans.
A doctor familiar with your medical history and overall health is the best person to explain your CBC results and what they mean for you.
Common terms used to describe CBC results are:
- anemia – not having enough healthy RBCs or hemoglobin
- leukopenia – a low number of WBCs
- neutropenia – a low number of neutrophils
- leukocytosis – an increased number of WBCs
- thrombocytopenia – a low number of platelets
- thrombocytosis – an increased number of platelets
CBC results can be low or high for many reasons. Some examples of abnormal CBC results related to cancer are listed below.
Abnormal RBC counts @(Model.HeadingTag)>
A low RBC count may be due to:
- anemia due to prolonged bleeding or blood loss (hemorrhage), a diet lacking iron or certain vitamins, certain types of chemotherapy, blood disorders or chronic disease
- Hodgkin lymphoma and other lymphomas
- cancers of the blood, such as
leukemia andmultiple myeloma - some myeloproliferative disorders
A high RBC count may be due to:
- dehydration, such as from severe diarrhea
- kidney tumours
- lung diseases
- polycythemia vera (a myeloproliferative disorder)
Abnormal WBC counts @(Model.HeadingTag)>
A low WBC count may be due to:
- viral infection
- severe bacterial infection
- bone marrow suppression caused by treatments like chemotherapy or radiation therapy
- bone marrow diseases, such as leukemia or
myelodysplastic syndrome (MDS) - anemia
A high WBC count may be due to:
- infection
- leukemia
- some
myeloproliferative disorders - some types of cancer, such as
bronchogenic carcinoma - certain drugs, such as
colony-stimulating factors - stress, allergies or tissue injury
Abnormal platelet counts @(Model.HeadingTag)>
A low platelet count may be due to:
- some types of cancer, such as leukemia or lymphoma
- autoimmune diseases
- bacterial infection
- viral infection
- chemotherapy or radiation therapy
- having many blood transfusions
- certain drugs, such as nonsteroidal anti-inflammatory drugs (NSAIDs) including acetylsalicylic acid (ASA, Aspirin, salicylate) and ibuprofen (Motrin, Advil, Nuprin)
A high platelet count may be due to:
- prolonged bleeding or blood loss (hemorrhage)
- anemia from low iron levels
- infection (inflammation)
- surgical removal of the spleen (splenectomy)
- polycythemia vera
- some types of leukemia
What happens if the results are abnormal @(Model.HeadingTag)>
Your doctor may recommend more tests, procedures, follow-up care or treatment. Sometimes therapies or doses may need to be changed to avoid problems when blood cell counts are low.
Special considerations for children @(Model.HeadingTag)>
Blood samples may need to be taken from very small blood vessels (called capillaries) in a finger or heel of an infant or young child. This is done by pricking the skin with a needle.
Preparing children before a test or procedure can help lower their anxiety, increase their cooperation and develop their coping skills. This includes explaining to children what will happen during the test, such as what they will see, feel and hear.
Parents or caregivers can help reassure and prepare children by giving them brief but accurate information about what will happen, such as:
- A big rubber band that feels like a balloon will be placed around your arm. This will feel tight, like someone is squeezing your arm.
- When your skin is cleaned it will feel cold.
- When the needle is placed in your arm, you will feel a prick or pinch. It may sting or hurt a little, or it may not hurt at all.
- Once the needle is in your arm, you will see the blood come out into a tube. You can look away if you don’t want to watch this.
Children may worry about not having enough blood after some has been taken from their arm. You can reassure them that bodies make new blood all the time and that their body will not run out of blood.
Ideas for helping children during blood tests @(Model.HeadingTag)>
Parents or caregivers can help distract children during blood tests to help make it easier for them.
Toddlers (1 to 2 years) might like to watch bubbles or toys that move or make sounds, such as magic wands, light-up toys or pinwheels. They may want to hold their favourite toy.
Preschoolers (3 to 5 years) may want to hold a favourite toy or watch toys that light up and make sounds.
School-age children (6 to 12 years) may want to:
- look at items, such as magic wands, light-up toys, video games and picture or “search and find” books
- bring their favourite stuffed animal or toy to hold
- blow bubbles or practise deep breathing while blowing bubbles
- imagine their favourite place
- hear a joke or story or tell you a joke or story
Teenagers (13 to 18 years) can try deep breathing or imagining their favourite place. They also might want to hear a joke or story.
Preparing a child for a blood test depends on the age and experience of the child. Find out more about helping your child cope with tests and treatments.
Expert review and references
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OneCare Media . Testing.com: Where Lab Tests Are Performed . 2015 : https://www.testing.com/.
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OneCare Media . Testing.com: Tips on Blood Testing . 2016 : https://www.testing.com/.
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OneCare Media . Testing.com: Complete Blood Count (CBC) . Seattle, WA : 2015 : https://www.testing.com/.
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American Cancer Society. Understanding Your Lab Test Results. 2016: https://www.cancer.org/treatment/understanding-your-diagnosis/tests/understanding-your-lab-test-results.html.
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American Society of Clinical Oncology. Complete Blood Count Tests. 2017: https://www.cancer.net/navigating-cancer-care/diagnosing-cancer/reports-and-results/complete-blood-count-tests.
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Cancer Research UK. Blood Tests. Cancer Research UK; 2015: http://www.cancerresearchuk.org/about-cancer/cancer-in-general/tests/blood-tests.
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Chabner BA, Chabner Thompson E. Cancer diagnosis. Beers MH, Berkow R (eds.). Merck Manual Professional Edition. 2013: http://www.merckmanuals.com/en-ca/professional/hematology-and-oncology/overview-of-cancer/cancer-diagnosis.
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CureSearch. Blood Studies. Bethesda, MD: National Childhood Cancer Foundation & Children's Oncology Group; https://curesearch.org/Blood-Studies.
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Fischbach FT, Fischbach MA. Fischbach's A Manual of Laboratory and Diagnostic Tests. 10th ed. Wolters Kluwer; 2018.
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Leukemia and Lymphoma Society of Canada. Blood Tests. http://www.llscanada.org/managing-your-cancer/lab-and-imaging-tests/blood-tests.
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National Cancer Institute. Understanding Laboratory Tests. 2013: https://www.cancer.gov/about-cancer/diagnosis-staging/understanding-lab-tests-fact-sheet.
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National Cancer Institute. How Cancer Is Diagnosed. 2015: https://www.cancer.gov/about-cancer/diagnosis-staging/diagnosis.
(Video) Hematology - Complete Blood Count (CBC) - Critical Care Labs -
National Heart, Lung, and Blood Institute; National Institute of Health. Blood Tests. Bethesda, MD: US National Library of Medicine; https://www.nhlbi.nih.gov/health-topics/blood-tests.
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Nemours Foundation. KidsHealth: Blood Test - Complete Blood Count. Nemours Foundation; 2011.
FAQs
What is included in a complete blood count CBC? ›
The CBC test identifies and counts the 7 types of cells found in the blood, red blood cell, neutrophil, eosinophil, basophil, lymphocyte, monocyte, and platelet.
What is a CBC blood test done for? ›A complete blood count (CBC) is a blood test. It gives your provider information about your blood and overall health. CBCs help providers diagnose, monitor and screen for a wide range of diseases, conditions, disorders and infections.
What are normal CBC levels? ›| Parameter | Males | Females |
|---|---|---|
| Hematocrit (%) | 40 to 50 | 35 to 43 |
| RBC count (×106/microL) | 4.2 to 5.7 | 3.8 to 5.0 |
| MCV (fL) | 82.5 to 98 | |
| MCHC | 32.5 to 35.2 | |
A full blood count (FBC) is a very common blood test that is also sometimes called a complete blood count (CBC) or full blood examination (FBE). It is a test for general health, but it can also provide information about a range of conditions.
What diseases can CBC detect? ›A complete blood count (CBC) is a blood test used to evaluate your overall health and detect a wide range of disorders, including anemia, infection and leukemia. A complete blood count test measures several components and features of your blood, including: Red blood cells, which carry oxygen.
What are the three main blood tests? ›A blood test is typically composed of three main tests: a complete blood count, a metabolic panel and a lipid panel.
Can a CBC detect heart problems? ›Complete blood count results can help a cardiologist detect complications of the pumping organ of the human body. CBC is used as a tool to detect CHF (Congestive Heart Failure) since it can diagnose anaemia which is known to induce CHF and create similar symptoms of CHF.
What cancers are detected by blood tests? ›- Hodgkin lymphoma.
- Leukemia.
- Non-Hodgkin lymphoma.
- Multiple myeloma.
When your doctor orders a CBC, there are no special preparations you'll need to take before the test. You are not required to fast (not eat solid foods for 12 hours or so), unless you are having other tests done at the same time that require it.
Does CBC show kidney function? ›Following are a variety of blood tests that help determine whether or not you have kidney disease: CBC – complete blood count of your red blood cells, white blood cells, and platelets—low CBC level can mean kidney function is reduced.
What causes low blood count? ›
Vitamin deficiency anemia.
Besides iron, your body needs folate and vitamin B-12 to produce enough healthy red blood cells. A diet lacking in these and other key nutrients can cause decreased red blood cell production. Some people who consume enough B-12 aren't able to absorb the vitamin.
Abnormal levels of red blood cells, hemoglobin, or hematocrit may be a sign of anemia, heart disease, or too little iron in your body. Low white cell count may be a sign of an autoimmune disorder, bone marrow disorder, or cancer. High white cell count may be a sign of an infection or a reaction to medicine.
Does a full blood count show diabetes? ›A finger prick test using a home testing kit may show you have high blood sugar levels but won't confirm you have diabetes. A normal blood test result will show you don't have diabetes. But the result will also show if you have diabetes or are at risk of developing type 2 diabetes.
What indicates infection in a blood test? ›White blood cells (also called leukocytes) fight bacteria, viruses, and other organisms your body identifies as a danger. A higher than normal amount of WBCs in your blood could mean that you have an infection. But too few WBCs can indicate you're at risk of developing an infection.
What happen if white blood cells are high? ›Produced in your bone marrow, they defend your body against infections and disease. But, when there are too many white blood cells, it usually means you have infection or inflammation in your body. Less commonly, a high white blood cell count could indicate certain blood cancers or bone marrow disorders.
What causes a high CBC count? ›Lifestyle factors that can cause a high red blood cell count include: Smoking cigarettes. Living at a high altitude. Taking performance-enhancing drugs such as anabolic steroids (for example, synthetic testosterone) or erythropoietin.
What should you not do before a blood test? ›Avoiding specific foods and drinks such as cooked meats, herbal tea, or alcohol. Making sure not to overeat the day before a test. Not smoking. Avoiding specific behaviors such as strenuous exercise or sexual activity.
Does a CBC show blood clots? ›A complete blood count (CBC) is one of the most common blood tests. It is usually done as part of a routine checkup and can help detect a number of blood disorders, such as anemia, infections, clotting problems, blood cancers, and immune system problems.
What are the most important blood tests? ›- Complete Metabolic and Lipid Panel. This is the test you might receive at an annual physical. ...
- Vitamin D-25 Hydroxy. ...
- Hemoglobin A1C. ...
- DHEA. ...
- Homocysteine. ...
- C-reactive protein. ...
- Thyroid-stimulating hormone. ...
- Testosterone (free testosterone)
Some test results will be ready the same day or a few days later, although others may not be available for a few weeks. You'll be told when your results will be ready and how you'll be given them.
What is included in a full blood panel? ›
Complete Blood Count (CBC)
A complete blood count test measures the range of a person's red blood cells, white blood cells, hemoglobin, hematocrit, and platelets.
For example, the red blood cell (RBC) count, hemoglobin (Hgb), and hematocrit (HCT) are the most important values needed to tell whether a person has anemia, but the red blood cell indices and the blood smear also help with the diagnosis and may show a possible cause for the anemia.
Can a CBC detect heart problems? ›Complete blood count results can help a cardiologist detect complications of the pumping organ of the human body. CBC is used as a tool to detect CHF (Congestive Heart Failure) since it can diagnose anaemia which is known to induce CHF and create similar symptoms of CHF.
How do you read a CBC report? ›When you get your report, you'll see two columns: a “reference range” and your results. If your results are inside the reference range, they're considered normal. If your results are higher or lower than the reference range, they're abnormal.
Can a CBC detect parasites? ›Blood parasites and some microorganisms are found by careful inspection of the blood cells during the CBC. In some cases, the results of the CBC will prompt your veterinarian to recommend other diagnostic tests.
What cancers are detected by blood tests? ›- Hodgkin lymphoma.
- Leukemia.
- Non-Hodgkin lymphoma.
- Multiple myeloma.
Following are a variety of blood tests that help determine whether or not you have kidney disease: CBC – complete blood count of your red blood cells, white blood cells, and platelets—low CBC level can mean kidney function is reduced.
What does it mean if your full blood count is abnormal? ›Abnormal levels of red blood cells, hemoglobin, or hematocrit may be a sign of anemia, heart disease, or too little iron in your body. Low white cell count may be a sign of an autoimmune disorder, bone marrow disorder, or cancer. High white cell count may be a sign of an infection or a reaction to medicine.
Does a CBC show blood clots? ›A complete blood count (CBC) is one of the most common blood tests. It is usually done as part of a routine checkup and can help detect a number of blood disorders, such as anemia, infections, clotting problems, blood cancers, and immune system problems.
Can CBC detect lung problems? ›Blood tests are not used to diagnose lung cancer, but they can help to get a sense of a person's overall health. For example, they can be used to help determine if a person is healthy enough to have surgery. A complete blood count (CBC) looks at whether your blood has normal numbers of different types of blood cells.
Does a full blood count detect blood clots? ›
Plasma proteins, such as fibrin, along with platelets work together to coagulate over the injury – preventing excess blood loss. By examining the plasma and platelets as part of a Full Blood Count blood test, this can give an insight into any potential bleeding or clotting conditions.
What indicates infection in a blood test? ›White blood cells (also called leukocytes) fight bacteria, viruses, and other organisms your body identifies as a danger. A higher than normal amount of WBCs in your blood could mean that you have an infection. But too few WBCs can indicate you're at risk of developing an infection.
What happen if white blood cells are high? ›Produced in your bone marrow, they defend your body against infections and disease. But, when there are too many white blood cells, it usually means you have infection or inflammation in your body. Less commonly, a high white blood cell count could indicate certain blood cancers or bone marrow disorders.
How does CBC diagnose leukemia? ›Complete blood count (CBC): This blood test lets your healthcare provider know if you have abnormal levels of red blood cells, white blood cells and platelets. If you have leukemia, you'll likely have higher than normal counts of white blood cells.
Do I need to fast for CBC blood test? ›When your doctor orders a CBC, there are no special preparations you'll need to take before the test. You are not required to fast (not eat solid foods for 12 hours or so), unless you are having other tests done at the same time that require it.
What are the symptoms of stomach worms? ›- Abdominal pain.
- Diarrhea.
- Nausea or vomiting.
- Gas or bloating.
- Dysentery (loose stools containing blood and mucus)
- Rash or itching around the rectum or vulva.
- Stomach pain or tenderness.
- Feeling tired.
In summary, the CBC cannot be used in isolation to differentiate bacterial from viral illness. The CBC can, however, augment clinical data from the history and physical examination to predict the likelihood of serious bacterial illness.