Complete blood count (CBC) results: what each part measures and typical ranges
A complete blood count is a group of blood tests that counts and sizes the cells in your blood: red cells, white cells and platelets. It is one of the most common blood tests and is often part of a checkup. (MedlinePlus CBC) (NHLBI)
What a CBC measures
- Red blood cells: carry oxygen from your lungs to the rest of your body. (MedlinePlus CBC)
- Hemoglobin: the iron-rich protein in red cells that carries the oxygen. (MedlinePlus CBC)
- Hematocrit: how much of your blood is made up of red cells. (MedlinePlus CBC)
- MCV (mean corpuscular volume): the average size of your red cells. Reports often add related numbers called MCH and MCHC, about the hemoglobin in each cell. (MedlinePlus CBC) (MedlinePlus RBC indices)
- White blood cells: fight infections and other diseases. A CBC gives the total; a CBC with differential also counts each of the five main types. (MedlinePlus CBC)
- Platelets: cell fragments that help your blood clot and stop bleeding. (MedlinePlus CBC) (NHLBI) Your platelet count is also one of the numbers in the FIB-4 liver score; see fatty liver screening and FIB-4.
Is it a screening test?
- USPSTF: a complete blood count is not on its list of recommended (A and B) services for adults without symptoms. (USPSTF A and B list) See blood tests by age for the blood tests that are.
- In pregnancy: for screening for iron deficiency and iron deficiency anemia in pregnant people, the USPSTF found the evidence insufficient to weigh the benefits and harms (I statement, 2024). (USPSTF, 2024) An I statement is not advice against testing; see USPSTF grades explained.
- Why it is still common: doctors often include it in a checkup to look at your overall health, and order it for symptoms such as tiredness, fever, weakness, bruising or bleeding, during treatments that can change blood counts, or to follow a long-term condition such as chronic kidney disease. (MedlinePlus CBC) (MedlinePlus encyclopedia) See what an annual physical includes.
The test itself
A health care professional takes a small sample of blood from a vein in your arm; it usually takes less than five minutes. No special preparation is usually needed, but you may need to fast if other tests are being done on the same sample. (MedlinePlus CBC) See fasting before a blood test.
Typical adult ranges, and why they differ
Three US government pages give three slightly different sets of adult ranges. That is normal: labs use different methods and so print different reference ranges, which are based on results from large groups of healthy people. Compare your result with the range on your own lab report, not with a table like this one, and use the same lab if you want to follow a trend. (MedlinePlus lab results)
| Part of the CBC | Unit | MedlinePlus test pages | MedlinePlus encyclopedia CBC page | NHLBI |
|---|---|---|---|---|
| Red blood cells, men | million cells per microliter | 4.2 to 5.7 (MedlinePlus RBC) | 4.6 to 6.2 (MedlinePlus encyclopedia) | 5 to 6 (NHLBI) |
| Red blood cells, women | million cells per microliter | 3.8 to 5.1 (MedlinePlus RBC) | 4.2 to 5.4 (MedlinePlus encyclopedia) | 4 to 5 (NHLBI) |
| Hemoglobin, men | grams per deciliter (g/dL) | 13.8 to 17.2 (MedlinePlus hemoglobin) | 13 to 18 (MedlinePlus encyclopedia) | 14 to 17 (NHLBI) |
| Hemoglobin, women | grams per deciliter (g/dL) | 12.1 to 15.1 (MedlinePlus hemoglobin) | 12 to 16 (MedlinePlus encyclopedia) | 12 to 15 (NHLBI) |
| Hematocrit, men | percent of blood volume | 37% to 48% (MedlinePlus hematocrit) | 40% to 55% (MedlinePlus encyclopedia) | 41% to 50% (NHLBI) |
| Hematocrit, women | percent of blood volume | 34% to 43% (MedlinePlus hematocrit) | 36% to 48% (MedlinePlus encyclopedia) | 36% to 44% (NHLBI) |
| MCV (average red cell size) | femtoliters | 79 to 95 (MedlinePlus RBC indices) | 80 to 100 (MedlinePlus encyclopedia) | Not used here (NHLBI) |
| White blood cells | cells per microliter | 4,500 to 11,000 (MedlinePlus WBC) | 4,500 to 11,000 (MedlinePlus encyclopedia) | 4,500 to 10,000 (NHLBI) |
| Platelets | per microliter | 150,000 to 400,000 (MedlinePlus platelets) | 150,000 to 400,000 (MedlinePlus encyclopedia) | 140,000 to 450,000 (NHLBI) |
- What changes the range: NHLBI notes that some ranges differ between men and women, and that age, high altitude and race can also affect them. (NHLBI) Red cell, hemoglobin and hematocrit levels rise for several weeks at higher altitude. (MedlinePlus hemoglobin) (MedlinePlus hematocrit)
- Units: some reports give white cells and platelets in billions per liter, so 4,500 per microliter appears as 4.5, and 150,000 as 150. (MedlinePlus WBC) (MedlinePlus platelets)
- Where the edges fall: MedlinePlus calls a white cell count below 4,500 per microliter low, a platelet count below 150,000 low and a platelet count of 400,000 or higher high. (MedlinePlus WBC) (MedlinePlus platelets)
The white cell differential
A differential reports each type of white cell as a percentage of all white cells. A rise in one type lowers the percentage of the others. (MedlinePlus differential)
| White cell type | Share of all white cells |
|---|---|
| Neutrophils | 40% to 60% (MedlinePlus differential) |
| Lymphocytes | 20% to 40% (MedlinePlus differential) |
| Monocytes | 2% to 8% (MedlinePlus differential) |
| Eosinophils | 1% to 4% (MedlinePlus differential) |
| Basophils | 0.5% to 1% (MedlinePlus differential) |
| Bands (young neutrophils) | 0% to 3% (MedlinePlus differential) |
What a high or low flag can mean
These are the general reasons the sources list. They are possibilities to look into, not a diagnosis.
- Low red cells, hemoglobin or hematocrit: can be a sign of anemia or bleeding. (NHLBI) Anemia has many causes, including blood loss, too little iron, folate or vitamin B12, long-term conditions such as chronic kidney disease, and pregnancy. (MedlinePlus encyclopedia) (MedlinePlus hemoglobin)
- High red cells, hemoglobin or hematocrit: are most often caused by low oxygen levels over a long time, for example from heart or lung disease. Other causes include dehydration, smoking, living at high altitude and a bone marrow disease that makes too many red cells. (MedlinePlus encyclopedia) (MedlinePlus hemoglobin)
- MCV: small red cells can point to low iron or thalassemia, and large red cells to low folate or vitamin B12 or to liver disease. This helps sort out what type of anemia is present. (MedlinePlus RBC indices) (NHLBI)
- High white cells: can come from an infection, inflammation, some medicines, smoking, pregnancy, severe physical or emotional stress, or a blood cancer such as leukemia. (MedlinePlus WBC)
- Low white cells: can follow a viral illness, some medicines, or come with an autoimmune or bone marrow problem. MedlinePlus also lists an inherited trait, not uncommon in African American people, that gives a lower count. (MedlinePlus WBC)
- Platelets: a low count can come from the bone marrow making too few or from platelets being destroyed; below 50,000 the risk of bleeding is higher. A high count can follow iron deficiency, an infection, surgery or injury, or come from a bone marrow disease. (MedlinePlus platelets) NHLBI notes that platelet levels outside the range may be a sign of a clotting or bleeding disorder. (NHLBI)
An abnormal level does not always mean you have a condition that needs treatment. Diet, activity, medicines, a menstrual period and not drinking enough water can all affect the results, and a CBC is only one of the tools your provider uses together with your history and symptoms. (MedlinePlus CBC) It is common for healthy people to have some results outside the range, and a normal result is not a guarantee of good health. (MedlinePlus lab results) Your doctor decides what your result means for you.
Where they differ: on whether to test, the USPSTF does not list a CBC among its recommended services for adults without symptoms, (USPSTF A and B list) while MedlinePlus and NHLBI describe it as often done in a routine checkup. (MedlinePlus CBC) (NHLBI) On the numbers, the platelet range is 150,000 to 400,000 on the MedlinePlus platelet page (MedlinePlus platelets) and 140,000 to 450,000 on the NHLBI page, (NHLBI) and the hematocrit and hemoglobin ranges differ as the table shows. Your own lab's range is the one your result is read against. (MedlinePlus lab results)
This page does not give diagnosis, diet, supplement, medicine or treatment advice. If you have a flagged result, see after an abnormal screening result for questions to ask.
Questions people ask
Is a CBC a routine screening test?
Not under the USPSTF: a complete blood count is not on its list of recommended (A and B) services for adults without symptoms. MedlinePlus and NHLBI note that it is often done as part of a routine checkup, and doctors also order it for symptoms, to monitor a long-term condition, or during treatments that can change blood counts. (USPSTF A and B list) (MedlinePlus CBC) (NHLBI) (MedlinePlus encyclopedia)
What is a normal hemoglobin level for an adult?
MedlinePlus gives about 13.8 to 17.2 g/dL for men and 12.1 to 15.1 g/dL for women, and NHLBI gives 14 to 17 and 12 to 15. Ranges vary between labs and with altitude, so compare your result with the range printed on your own lab report. (MedlinePlus hemoglobin) (NHLBI) (MedlinePlus lab results)
What is a normal platelet count?
About 150,000 to 400,000 per microliter, which some reports write as 150 to 400. A count below 150,000 is low and 400,000 or higher is high. NHLBI gives a slightly wider range of 140,000 to 450,000. (MedlinePlus platelets) (NHLBI)
Does a CBC need fasting?
Usually not. You may need to fast if other tests are being done on the same blood sample; your provider will tell you if there are special instructions. (MedlinePlus CBC)
Does a result outside the range mean something is wrong?
Not always. It is common for healthy people to have some results outside the reference range, and things such as activity level, medicines, a menstrual period or not drinking enough water can affect a CBC. A result inside the range is not a guarantee of good health either. Your doctor decides what your result means for you. (MedlinePlus lab results) (MedlinePlus CBC)