CBC Blood Test: What It Shows and What It Does Not
Quick answer: A CBC counts and sizes your red blood cells, white blood cells and platelets. It is one of the most common blood tests and is used to look for anemia, infection and other blood conditions. A result outside the range is a clue, not a diagnosis.
About this test
A complete blood count measures the number and size of your red blood cells, white blood cells and platelets. It also reports hemoglobin, the oxygen carrying protein in red cells, hematocrit, the share of your blood made up of red cells, and average red cell size (MCV). The differential breaks white cells into their types.
Why is it ordered?
- A routine check of general health.
- Looking for anemia, infection or immune conditions.
- Following a blood condition or a treatment that affects blood cells.
- Looking at causes of tiredness, pale skin or hair thinning, usually together with iron tests.
What results may show
- Low red cells, hemoglobin or hematocrit can go along with anemia, low iron or other causes.
- High red cell values can go along with dehydration or other conditions.
- White cell counts outside the range can relate to infection, medicine reactions, immune conditions or bone marrow conditions.
- Platelet counts relate to how your blood clots.
What this test may not show
- It does not identify the cause of an abnormal result on its own. Providers often order more tests.
- A normal CBC does not always rule out low iron stores. Ferritin and iron tests look at iron directly.
- Diet, activity, medicines, menstrual periods and hydration can change results.
- An abnormal result does not always mean a medical condition.
How to prepare
- No special preparation is usually needed.
- Fasting may be needed only if other tests are drawn from the same sample. Follow any instruction given when you order.
Where you can get this test
| Option | Price | Includes |
|---|---|---|
| Wellness Panel | $149 | CBC, CMP, lipid panel, vitamin D, A1c, hs-CRP, urinalysis, TSH |
| Comprehensive Health Panel, Women’s | $149 | CBC, CMP, lipid panel, vitamin D, A1c, hs-CRP, urinalysis, TSH |
| Comprehensive Health Panel, Man | $149 | CBC, CMP, lipid panel, total testosterone, A1c, hs-CRP, urinalysis, TSH |
| Hair Loss Panel | $199 | CBC, ferritin, iron and TIBC, TSH, free T4, vitamin D, total testosterone, DHEA-S |
The Anemia Panel also includes the main blood count markers: red cells, white cells, hemoglobin, hematocrit and platelets.
A doctor’s visit is not required to order. Order online, then visit our Buffalo Grove or Lake Zurich location for the sample. Review results with your own healthcare provider.
Related tests
- Ferritin: Ferritin is a protein that stores iron, so a ferritin test shows roughly how much iron your body has in storage.
- Iron and TIBC: An iron and TIBC test measures the iron circulating in your blood and how much iron your blood can carry.
- Browse the full Lab Test Library
Frequently asked questions
What does a CBC measure?
Red cells, white cells and platelets, plus hemoglobin, hematocrit and red cell size.
Can a CBC show iron deficiency?
It can show signs such as low hemoglobin or small red cells, but ferritin and iron tests look at iron directly.
Do I need to fast for a CBC?
Usually not. Follow any instruction given when you order, especially if other tests are drawn at the same time.
What does a differential mean?
It counts each type of white blood cell separately.
Sources
Medically reviewed by Rodion Levin, FNP-C, Founder and Medical Director. This page is for general education. It does not diagnose a condition or replace advice from your healthcare provider.
