How to read blood test results

This page was reviewed under our medical and editorial policy by

Bradford Tan, MD, Chair, Department of Pathology and Laboratory Medicine, City of Hope Atlanta, Chicago and Phoenix

This page was reviewed on September 25, 2022.

If my blood tests are normal, can I have cancer?

Yes, it’s possible to still have cancer despite normal blood tests, since routine blood work alone can’t detect most cancers. Leukemia is the only cancer that may be detected in routine blood work.

Blood tests may be performed every few weeks or months so the care team can compare the results over time.

It’s helpful to go over test results with the cancer care team and ask them to explain the results. That's also a good time to ask any questions and request a copy of the blood work results for the patient's records.

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

Questions to ask about blood work

Questions to ask before a blood test:

  • What will this test reveal?
  • How will the test results be shared?
  • How is this test done?
  • Are any changes required of the patient's routine before the test, such as not having anything to eat or drink?

Questions to ask after a blood test:

  • What do the test results mean?
  • How accurate is this test?
  • What are the next steps?
  • Are more tests necessary?
  • Will this test be repeated? If so, when?

Complete blood count (CBC) test

A CBC is one of the most common blood tests. It measures the main components of the patient's blood.

Can a CBC detect cancer?

A CBC test may be used to diagnose some blood cancers, such as leukemia, but it isn't typically used to diagnose solid tumor cancers, such as breast cancer or lung cancer.

It’s also common to have a CBC test after receiving a cancer diagnosis, to help the care team get a bigger picture of the patient's overall health.

A CBC test can help the care team:

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

CBC components

White blood cells

These cells help the 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. The care team will pay close attention to the patient's neutrophil level. Low levels of neutrophils may mean he or she is at higher risk of an infection.

Red blood cells

These cells carry oxygen to cells throughout the body, and they carry carbon dioxide away. 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 the patient to feel tired and lack energy. High levels may indicate dehydration.


Platelet cells help the blood clot, which helps control bruising and bleeding when the patient has a wound or injury. The patient's platelet count can help his or her care team know if he or she is at high risk for bleeding problems.

CBC test results

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.

Complete blood count normal ranges

The normal ranges below are measured in cells per microliter (mcL).

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


Keep in mind that there are many reasons why certain levels could be abnormal. Factors such as recent diet and activity may affect the results. The patient's cancer care team can help him or her understand the results, catch things early and avoid complications.

CBC with differential

A CBC with differential measures the components above, as well as assessing each type of white blood cell. The cancer care team may order these tests to track the status of the patient’s disease, evaluate what may be causing specific symptoms (such as fatigue or bruising) or to monitor the patient’s overall health.

Comprehensive metabolic panel (CMP) test

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

A CMP measures substances like:

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

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

Some side effects from cancer treatment—like vomiting and diarrhea—may cause the patient to be dehydrated, which can affect blood chemistry, too. The patient won’t feel these changes in his or her blood chemistry level until it’s a bigger problem.

CMP blood test components

A CMP measures many different substances, and each one tells the care team something different about the patient's body. The care team may monitor electrolytes, for example, to see how the patient is handling treatments and to make sure he or she isn't dehydrated. They may monitor certain waste products to see how well the patient's kidneys or liver are working. And they may look at enzyme and protein results to see how the patient's liver is functioning.

Check with the care team, as the patient may need to fast before having a CMP.

The 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.

Chart: CMP blood test results explained

Comprehensive metabolic panel normal ranges, according to the National Library of Medicine, are as follows, measured in grams (g), milligrams (mg), micrograms (U) and milliequivalents (mEq) per liter (L) or deciliter (dL).

CMP blood test component Normal range
Albumin, liver protein 3.4 to 5.4 g/dL
ALP (alkaline phosphatase), liver enzyme 20 to 130 U/L
ALT (alanine aminotransferase), liver enzyme 4 to 36 U/L
AST (aspartate aminotransferase), liver enzyme 8 to 33 U/L
BUN (blood urea nitrogen), kidney waste product 6 to 20 mg/dL
Calcium, mineral 8.5 to 10.2 mg/dL
Chloride, electrolyte 96 to 106 mEq/L
CO2 (carbon dioxide), electrolyte 23 to 29 mEq/L
Creatinine, kidney waste product 0.6 to 1.3 mg/dL
Glucose, sugar 70 to 100 mg/dL
Potassium, electrolyte 3.7 to 5.2 mEq/L
Sodium, electrolyte 135 to 145 mEq/L
Total bilirubin, liver waste product 0.1 to 1.2 mg/dL
Total protein, blood protein 6.0 to 8.3 g/dL

How long do blood test results take?

The timing of blood test results depend on the specific test the care team ordered and where testing was performed, but results are typically available within three to five days following the blood draw. 

In some cases, the provider who ordered the test will call the patient with the results or set up a follow-up appointment to discuss them, while in other instances, the results may show up in the patient’s health care online portal as soon as they’re ready. Talk to the care team about when to expect blood test results.

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Show references
  • American Cancer Society (2023, October 23). Understanding Your Lab Test Results.
  • Ried K, Eng P, Sali A (2017). Screening for Circulating Tumour Cells Allows Early Detection of Cancer and Monitoring of Treatment Effectiveness: An Observational Study. Asian Pacific Journal of Cancer Prevention, 18(8), 2275–85.
  • Lin D, Shen L, Luo M, et al. (2021, November 22). Circulating tumor cells: biology and clinical significance. Signal Transduction Targeted Therapy, 6.
  • National Cancer Institute: SEER Training Modules. Tumor Markers.
  • National Cancer Institute: SEER Training Modules. Lab Tests.
  • Menarini Silicon Biosystems (2021, September 22). How Are the Results Interpreted and What Do They Mean?
  • American Society of Clinical Oncology (2022, September). Understanding Your Complete Blood Count (CBC) Tests.
  • U.S. National Library of Medicine (2022, April 4). Complete Blood Count (CBC)
  • U.S. National Library of Medicine (2022, October 16). CBC Blood Test.
  • U.S. National Library of Medicine (2021, September 9). Comprehensive Metabolic Panel (CMP).
  • U.S. National Library of Medicine (2022, March 21). Comprehensive Metabolic Panel.
  • U.S. National Library of Medicine (2021, March 9). Basic Metabolic Panel (BMP).