A complete blood count (CBC) is a group of blood tests that measure the number, types, and size of the cells in your blood. It reports red blood cells (which carry oxygen), white blood cells (which help fight infection), and platelets (which help blood clot), along with hemoglobin (the oxygen-carrying protein in red cells), hematocrit (the fraction of blood made up of red cells), and red blood cell indices such as MCV, MCH, and MCHC (the average size and hemoglobin content of your red cells). Only a small blood sample, usually drawn from a vein in your arm, is needed.
A CBC is often part of a routine checkup. A healthcare provider may also order it to help detect, diagnose, or monitor conditions that can affect blood cell counts — such as anemia, infections, immune system disorders, and blood cancers — or to keep an eye on an existing condition or a treatment that may change these counts.
These are general reference ranges from MedlinePlus, provided only as broad context. Reference ranges vary by laboratory, and by a person's age, sex, and the testing method or sample used — some labs use different measurements. The specific ranges printed on your own lab report are the ones that apply to your results, and only your healthcare provider can interpret what your numbers mean for you. This is not a personal diagnostic cutoff. - Red blood cell (RBC) count: about 4.6–6.2 million cells/mcL (male); 4.2–5.4 million cells/mcL (female) - White blood cell (WBC) count: about 4,500–11,000 cells/mcL - Hemoglobin: about 13–18 g/dL (male); 12–16 g/dL (female) - Hematocrit: about 40%–55% (male); 36%–48% (female) - MCV: about 80–100 femtoliters - MCH: about 27–32 pg/cell - MCHC: about 32–36 g/dL - Platelet count: about 150,000–400,000/mcL
Higher-than-usual values are general possible associations, not a diagnosis, and the lists below are not complete. A higher RBC count, hemoglobin, or hematocrit can be seen with dehydration, kidney disease, chronically low oxygen levels, smoking, or a condition called polycythemia vera, among others. A high white blood cell count may be seen with infections, inflammatory conditions such as lupus or rheumatoid arthritis, certain medicines, severe physical or emotional stress, tissue injury, or blood disorders such as leukemia. A high platelet count can be seen with bleeding, iron deficiency, certain blood diseases, or some cancers. An abnormal result does not always mean there is a medical condition that needs attention, because diet, activity, medicines, menstrual periods, not drinking enough water, and other everyday factors can also affect results.
Lower-than-usual values are also general possible associations, hedged and incomplete, not a diagnosis. A low RBC count, hemoglobin, or hematocrit may suggest anemia, which can be related to blood loss, iron or other nutritional deficiency, chronic disease, bone marrow problems, or the breakdown of red blood cells, among other causes. A low white blood cell count may be seen with some infections, autoimmune conditions, bone marrow problems, liver disease, chemotherapy, or certain medicines. A low platelet count can be seen with an enlarged spleen, certain immune or bone marrow conditions (including the effects of chemotherapy), or pregnancy. As with high values, a low result does not by itself confirm any specific condition — your results are best understood together, alongside your symptoms, history, and any other tests, and your healthcare provider is the one who interprets what a CBC means in your specific situation. This is general information, not medical advice.
Reference ranges vary by laboratory, age, sex, and method — the range on your own report is what applies to you. A single value out of range doesn’t confirm any condition; your clinician interprets it alongside your symptoms, history, and other results. This page is general information, not medical advice.
General reference, not medical advice, and not a substitute for your clinician. Lab reference ranges and interpretation depend on the laboratory and on your individual situation — discuss your results with a licensed healthcare professional.