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Lab test
What does a complete blood count (CBC) show, and what are normal ranges?
A complete blood count (CBC) counts red blood cells, white blood cells and platelets and measures hemoglobin and hematocrit. It is ordered in routine checkups and to look for anemia, infection and other conditions. The NHLBI lists adult hemoglobin of about 14 to 17 g/dL for men and 12 to 15 g/dL for women.
What does the CBC test measure?
A CBC counts the cells in your blood: red blood cells, white blood cells and platelets. It also measures hemoglobin, the protein that carries oxygen, and hematocrit, the share of blood made up of red cells. MedlinePlus
Red cell indices such as mean corpuscular volume (MCV) describe the average size of red blood cells. NHLBI
Why is the CBC test ordered?
- As part of a routine checkup, or to look into symptoms such as fatigue. MedlinePlus
- Abnormal red cell, hemoglobin or hematocrit levels may be a sign of anemia, dehydration, heart disease or too little iron. MedlinePlus
- A high white cell count may be a sign of infection or a reaction to a medicine; a low count may point to an autoimmune or bone marrow disorder. MedlinePlus
What are typical CBC ranges?
The NHLBI publishes these typical adult ranges, and notes that red cell, hemoglobin and hematocrit values vary with altitude. NHLBI
Reference ranges differ between laboratories and testing methods, and many also differ by age, sex, pregnancy or the phase of the menstrual cycle. The range printed on your own report is the one that applies to your result, and a clinician interprets it alongside your history.
| Measure | Adult men | Adult women |
|---|---|---|
| Red blood cells | 5 to 6 million cells/mcL | 4 to 5 million cells/mcL |
| Hemoglobin | 14 to 17 g/dL | 12 to 15 g/dL |
| Hematocrit | 41 to 50 percent | 36 to 44 percent |
| Mean corpuscular volume | 80 to 95 fL | 80 to 95 fL |
What can affect CBC results?
- Diet, activity level, medicines, having a menstrual period and not drinking enough water can all affect CBC results. MedlinePlus
- Living at higher altitude changes red cell, hemoglobin and hematocrit values. NHLBI
When should you talk to a clinician about a CBC result?
- A result outside the printed range does not always mean a condition that needs treatment; ask the clinician who ordered it what it means for you. MedlinePlus
- A CBC is one tool; a clinician considers it with your history, symptoms and other tests. MedlinePlus
DiscoverMedica explains what a test measures and what named sources publish. It does not interpret individual results; the clinician who ordered your test, or one you choose, does.
Where can you get a CBC test?
A clinician can order it as part of routine or follow-up care. Some services also let you order lab tests yourself; check that a service’s panel includes this marker, which laboratory runs it, and who reviews the result with you.
- Function HealthAnnual membership for broad lab panels, drawn at Quest sites or at home.
- Quest HealthOrder individual lab tests from Quest Diagnostics online, without a doctor’s visit.
CBC (Complete Blood Count): questions, answered
What is a normal hemoglobin level?
The NHLBI lists a typical adult range of 14 to 17 g/dL for men and 12 to 15 g/dL for women, and notes that hemoglobin varies with altitude. Laboratories print their own ranges, so compare a result with the range on your report and ask the clinician who ordered it what it means for you.
Do I need to fast for a CBC?
A CBC on its own usually needs no fasting, but it is often drawn with other tests, such as a metabolic panel, that may. Follow the instructions from whoever orders the tests, and mention any medicines you take, since MedlinePlus lists medicines among the factors that can affect results.
Can a CBC detect iron deficiency?
A CBC can show low hemoglobin, low hematocrit or small red blood cells, which MedlinePlus lists as possible signs of too little iron. It cannot confirm the cause on its own, so clinicians often add ferritin and iron tests to look at iron stores directly.
Sources
Last reviewed October 7, 2026. Every source above was checked on or before that date. Educational information only, not medical advice; it does not replace a conversation with a licensed clinician. DiscoverMedica does not employ clinicians.
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