Complete Blood Count (CBC) Test
Overview
A complete blood count (CBC) is a laboratory blood test that checks the levels and types of cells in the blood. It helps doctors assess a person’s general health and can give early clues about a variety of conditions such as infection, anemia, or problems with blood clotting.
Key elements measured in a CBC include:
| Component | Role in the Body |
|---|---|
| Red blood cells | Deliver oxygen to tissues. |
| White blood cells | Defend against infections. |
| Hemoglobin | Holds and moves oxygen in red blood cells. |
| Hematocrit | Measures red blood cell concentration. |
| Platelets | Help the blood to clot. |
By looking at these values, health professionals can spot if any results are higher or lower than expected, which may need more blood tests or lab investigations.
Reasons for Testing
A complete blood count (CBC) helps healthcare providers learn more about a person’s well-being. This test checks the amounts of different blood cells and can show signs of health problems. The results help guide decisions about other testing or care.
Additional Details
A CBC is useful in several situations:
- Detecting Blood Disorders: Low or high numbers of certain cells can point to anemia, leukemia, or clotting problems.
- Finding the Cause of Symptoms: Issues like tiredness, bruising, or lasting fevers may be linked to abnormal blood cell counts.
- Monitoring Current Health Problems: Some conditions change blood cell levels over time. By repeating the CBC, doctors can track these changes.
- Observing Treatment Effects: Medicines or therapies like chemotherapy sometimes affect blood cells. The CBC helps check if these treatments are safe for the patient.
Here is a table listing some conditions for which a CBC may provide helpful details:
| Condition | Category |
|---|---|
| Anemia | Blood disorder |
| Chronic lymphocytic leukemia | Cancer |
| Lupus | Autoimmune disease |
| Uterine fibroids | Reproductive disorder |
| Thalassemia | Blood disorder |
| Heart disease | Cardiovascular condition |
| Fibromyalgia | Chronic pain condition |
| Tonsillitis | Infection |
| Porphyria | Rare disorder |
Getting Ready for the Test
Most people do not need to change their diet or routine before a complete blood count test. Normal eating and drinking is allowed if the test is only for a blood count. If the blood will be checked for other things, it may be necessary to fast for several hours. Check with your health provider for clear instructions.
What You Might Experience
During a complete blood count, a healthcare professional collects a small blood sample from a vein in the arm, often near the elbow, using a needle. The lab then analyzes the blood.
- Most people can return to normal activities right after the procedure.
- No special recovery or aftercare is needed.
- The process is quick and usually causes minimal discomfort.
Lab Findings
Not a Conclusive Assessment
A complete blood count (CBC) by itself often does not confirm or rule out health conditions. This test’s measurements may sometimes fall outside the typical range even when a person is healthy and has no symptoms.
If results are only slightly high or low, and there are no other signs of illness, no action might be needed. However, for individuals with ongoing medical problems, such as those receiving treatment for cancer, abnormal readings could mean a treatment adjustment is necessary.
When CBC results show numbers much higher or lower than expected, a healthcare provider may recommend seeing a specialist called a hematologist, who deals with disorders of the blood.
Possible Health Insights from the Results
Lab results from a CBC can reveal patterns or unusual findings linked to a range of health issues. Each major component relates to different body functions:
Red Blood Cell Measures
- Red blood cell count, hemoglobin, and hematocrit give information about oxygen transport in the body.
- Low levels of these may signal anemia. Common causes of anemia include blood loss, not enough iron, or specific health conditions. People with anemia can feel weak, tired, or short of breath.
- If any of these are above the usual range, it could mean erythrocytosis, which is sometimes related to blood cancers, heart disease, or problems with the bone marrow.
Normal Ranges Table
| Measure | Typical Range (Male) | Typical Range (Female) |
|---|---|---|
| Red Blood Cell Count | 4.35–5.65 trillion cells/L | 3.92–5.13 trillion cells/L |
| Hemoglobin | 13.2–16.6 g/dL | 11.6–15 g/dL |
| Hematocrit | 38.3%–48.6% | 35.5%–44.9% |
White Blood Cell Count
- White blood cell count helps point to infections, inflammation, immune system activity, and more.
- A low white blood cell count (leukopenia) may come from bone marrow problems, autoimmune diseases, cancer, or side effects from medicine. It may make a person more likely to get infections.
- High white blood cell levels usually happen with infections or inflammation, but they may also result from immune system disorders, reactions to medicine, hard exercise, or blood cancers like leukemia.
| Type | Typical Range |
|---|---|
| White Blood Cells | 3.4–9.6 billion cells/L |
Platelet Count
- Platelets are important for blood clotting.
- Fewer platelets than normal (thrombocytopenia) might suggest bone marrow disorders, vitamin deficiencies, or a side effect from certain medicines. It may lead to increased bruising or bleeding.
- More platelets than usual (thrombocytosis) can be related to infections, blood loss, inflammation, or some forms of cancer.
- If platelet numbers are very abnormal, doctors will want to find out why with more tests.
| Measure | Typical Range (Male) | Typical Range (Female) |
|---|---|---|
| Platelet Count | 135–317 billion/L | 157–371 billion/L |
Conditions Linked to CBC Values
- Anemia: Low red blood cells, hemoglobin, or hematocrit.
- Iron Deficiency: Often leads to anemia with low values.
- Sickle Cell Disease: Changes shape and count of red blood cells; shown in certain CBC patterns.
- Infection or Inflammation: Causes high white blood cell counts.
- Leukopenia/Neutropenia: Low white blood cells or neutrophils; can mean bone marrow problems or immune issues.
- Leukemia: Cancer that affects the bone marrow; can cause very high or very low blood cell counts.
- Bleeding Problems: Seen as low platelets or low red cell counts.
- Blood Cancers: May affect any measure.
List of CBC Results That May Need Further Review
- Red blood cell count above or below normal.
- Hemoglobin out of the typical range.
- Hematocrit not in the expected range.
- White blood cell count very high or very low.
- Platelet count much higher or lower than standard values.
If any of these are found, more testing and evaluation are often needed. The right steps depend on symptoms, history, and other lab findings.
