How to read blood test results

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on April 22, 2022.

There are several blood tests that your care team may order to help them find, diagnose or treat cancer, or monitor how your treatment is affecting you. Each test measures different substances in your blood.

Your care team will order different laboratory tests depending on what they’re looking for. They may ask for blood test results every few weeks or months so they can compare the results over time.

It’s helpful to go over your test results with your cancer care team and ask them to explain the results to you. Make sure to ask any questions you have. You may also want to ask for a copy of the test results for your records.

Asking your care team questions about your tests is a great way to learn more about your care and treatment. Consider asking the questions below before and after the test.

Questions to ask before the test:

  • What will this test tell us?
  • How will I get my test results?
  • How is this test done?
  • Do I need to change my routine before the test, such as not having anything to eat or drink?

Questions to ask after the test:

  • What do my test results mean?
  • How accurate is this test?
  • What are my next steps?
  • Do I need more tests?
  • When is the next time I’ll have this test?

Complete blood count (CBC) test results

A CBC test is one of the most common blood tests. It measures the main components of your blood.

A CBC test may be used to diagnose some blood cancers, such as leukemia. It’s also common to have a CBC test after you’ve been diagnosed, to help your care team get a bigger picture of your overall health.

A CBC test can help your care team:

  • See if cancer has spread to bone marrow
  • Monitor how your body is reacting to treatment, such as chemotherapy 
  • Diagnose another condition you might have, like anemia (low blood iron) or an infection

Main components of a CBC test

White blood cells

These cells help your body fight infection. There are many different types of white blood cells, each with its own specific job. A CBC shows the levels of several types of white blood cells, called neutrophils, lymphocytes, monocytes, eosinophils and basophils. Your care team will pay close attention to your neutrophil level. Low levels of neutrophils may mean you’re at higher risk of an infection.

Red blood cells

These cells carry oxygen to cells throughout the body, and they carry carbon dioxide away from your cells. In addition to an overall red blood cell count, a CBC measures the levels of hemoglobin (a part of the red blood cell that is rich in iron) and hematocrit (the percent of red blood cells in the blood). Low levels of red blood cells indicate anemia, which can cause you to feel tired and lack energy. High levels may indicate dehydration.


Platelet cells help your blood clot, which helps control bruising and bleeding when you have a wound or injury. Your platelet count can help your care team know if you’re at high risk for bleeding problems.

Complete blood count normal ranges

The numbers below show what the normal ranges for the main components of a CBC look like. Some components have different normal ranges for women and men.

Normal ranges for CBC components:

  • White blood cells (WBC):
    • Women: ;4,500 to 10,000 cells/mcL
    • Men: 4,500 to 10,000 cells/mcL
  • Red blood cells (RBC):
    • Women: 4.2 to 5.4 million cells/mcL
    • Men: 4.7 to 6.1 million cells/mcL
  • Hemoglobin (Hgb):
    • Women: 12.1 to 15.1 gm/dL
    • Men: 13.8 to 17.2 gm/dL
  • Hematocrit (Hct):
    • Women: 36.1% to 44.3%
    • Men: 40.7% to 50.3%
  • Platelets (Plt):
    • Women: 150,000 to 450,000/dL
    • Men: 150,000 to 450,000/dL

Keep in mind that there are many reasons that certain levels could be abnormal. Factors such as recent diet and activity may affect the results. Your cancer care team can help you understand your results, catch things early and avoid complications.

Comprehensive metabolic panel (CMP) results

A comprehensive metabolic panel—also called a blood chemistry panel—is another type of blood test that measures 14 different substances in your blood. This blood test can help your care team get information about your metabolism, or how your body is using food and spending energy.

A CMP measures substances like:

  • Sugars
  • Fats (lipids)
  • Proteins
  • Electrolytes
  • Enzymes

Your care team may use a CMP to see how your body is responding to treatment. Some treatments can change the level of certain substances in your blood.

Some side effects from treatment—like vomiting and diarrhea—may cause you to be dehydrated, which can affect your blood chemistry, too. You won’t feel these changes in your blood chemistry level until it’s a bigger problem.

A CMP measures many different substances, and each one tells your care team something different about your body. Your care team may monitor electrolytes, for example, to see how you’re handling treatments and to make sure you’re not dehydrated. They may monitor certain waste products to see how well your kidneys or liver are working. And they may look at enzyme and protein results to see how your liver is functioning.

Check with your doctor, as you may need to fast before having a CMP.

Your care team may also order a basic metabolic panel (BMP) depending on the information they need. A BMP measures only eight of the substances that a CMP does and doesn’t include testing liver function and proteins.

Comprehensive metabolic panel normal ranges, according to the National Library of Medicine:

  • BUN (blood urea nitrogen), kidney waste product: 20 mg/dL
  • Calcium, mineral: 8.5–10.2 mg/dL
  • Carbon dioxide, electrolyte: 23–29 mEq/L
  • Chloride, electrolyte: 96–106 mmol/L
  • Creatinine, kidney waste product: 0.6–1.3 mg/dL
  • Glucose, sugar: 70–100 mg/dL
  • Potassium, electrolyte: 3.7–5.2 mEq/L
  • Sodium, electrolyte: 135–145 mEq/L
  • Albumin, liver protein: 3.5–5.4 g/dL
  • ALP (alkaline phosphatase), liver enzyme: 20–130 U/L
  • ALT (alanine transaminase), liver enzyme: 4–36 U/L
  • AST (aspartate aminotransferase), liver enzyme: 8–33 U/L
  • Bilirubin, liver waste product: 0.1–1.2 mg/dL
  • Total protein, blood protein: 6.0–8.3 g/dL

Circulating tumor cells (CTC) results

If your care team has diagnosed or suspects you have metastatic breast, prostate or colorectal cancer, results from a CTC test may help them learn more about your cancer. For these cancers, CTC test results can help your care team find cancer early, provide a prognosis (likelihood of recovery) and monitor how cancer treatment is working.

Circulating tumor cells come from a tumor. Most tumors shed fragments of dead cells, which then flow into the bloodstream. If the tumor has shed enough cells, a CTC test may help your care team know more about your cancer. That’s true of even a very small, undetectable tumor.

CellSearch™ circulating tumor cell (CTC) test results

The CTC test is also called the CellSearch™ CTC test. A description of CTC test result ranges is shown below.

  • Favorable, usually indicates a better prognosis:
    • Metastatic breast cancer: 0-4 CTCs
    • Metastatic prostate cancer: 0-4 CTCs
    • Metastatic colorectal cancer: 0-2 CTCs
  • Unfavorable, usually indicates a worse prognosis:
    • Metastatic breast cancer: ≥ 5 CTCs
    • Metastatic prostate cancer: ≥ 5 CTCs
    • Metastatic colorectal cancer: ≥ 3 CTCs

Lower CTC numbers tend to mean that the cancer will be slower to progress (meaning to grow or get worse) and that the patient may survive longer than if the test showed higher numbers. Higher numbers tend to mean the cancer will grow or get worse faster and that there’s less chance the patient will recover.

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