Blood Tests for Cancer

Blood testing is a tool healthcare providers use to help diagnose and manage cancer. Examples include complete blood count and tumor markers. The results can provide important information about overall health, organ function and potential disease. But they should be considered along with other factors and tests.


Can you detect cancer with a blood test?

Blood testing is one of many tools healthcare providers use to diagnose and manage cancer. The tests can provide important information about:

  • Chemicals and proteins in your blood that might indicate cancer.
  • Levels of blood cells that are too high or too low, perhaps because of cancer.
  • Overall health.
  • Organ function.
  • Stage of cancer.
  • Treatment options.
  • Whether treatment is working or the disease is progressing.
  • Whether cancer has come back (recurrence).

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What tests are done to check for cancer?

Blood tests for cancer fall into four general categories:

  • Complete blood count (CBC).
  • Tumor markers.
  • Blood protein testing.
  • Circulating tumor cell tests.

Although blood tests are useful in cancer diagnosis, they’re not used by themselves. Other tests are almost always necessary, including:

What cancers are detected by blood tests?

Blood tests can be useful in all types of cancer, particularly blood cancers such as:


Who performs blood tests for cancer?

Blood tests take place in a doctor’s office, clinic, lab or hospital. They’re performed by many healthcare providers, often lab technicians and nurses.

What is a complete blood count?

A complete blood count (CBC) measures three types of blood cells circulating in your bloodstream. The results can help healthcare providers diagnose cancer or detect whether cancer has spread.

In addition, some cancer treatments can affect blood counts, so your healthcare provider may recommend regular CBCs as you’re going through treatment.

Each type of blood cell has a range that’s considered normal or healthy. Labs use ranges because the number can vary from person to person or within the same person from day to day.

The three cell types and their ranges are:

  • Platelets, which help blood clot. The normal range for platelet count is 150,000/milliliter (mL) to 400,000/mL.
  • Red blood cells, which deliver oxygen throughout your body. Red blood cells may be measured in two different ways. Hematocrit is the proportion of red blood cells in your blood. The normal range for men is 40% to 55% and for women is 36% to 48%. Hemoglobin is a protein in red blood cells. The normal range for men is 13.0/deciliter (dL) to 17.0 g/dL and for women is 11.5/dL to 15.5 g/dL.
  • White blood cells, which fight infection. The normal range for white blood cells is 5,000/mL to 10,000/mL.

Many factors can affect your CBC. Your healthcare provider will help you understand what your numbers mean. The results must be considered along with other factors, such as symptoms and additional test results.


What are tumor markers?

Tumor markers are substances made by cancerous cells or your body’s normal cells in response to cancer. Some tumor markers indicate a specific type of cancer. Others can indicate several different types of cancer.

Scientists are still learning about known tumor markers and discovering new tumor markers. Some tumor markers currently used include:

If a blood test detects a tumor marker, your healthcare provider will discuss what that means and recommend additional testing.

What is blood protein testing?

Blood protein testing uses a special process called electrophoresis to find certain proteins in your blood. The proteins are called immunoglobulins, which your immune system releases in response to diseases such as myeloma.

What is a circulating tumor cell test?

A new type of blood test for cancer looks for circulating tumor cells. These cells have broken off from a tumor and are in your bloodstream. This may indicate that cancer is spreading (metastasizing). The test can currently help monitor certain types of cancer, such as breast, prostate and colorectal cancers. Scientists are still developing the technology.

Test Details

How do I prepare for a blood test?

Your healthcare provider will give you specific instructions on how to prepare for your blood test. The instructions may differ depending on the type of test and other bloodwork you’re having at the same time.

You may have to fast for eight to 12 hours. That means you shouldn’t eat or drink anything besides water. You also may have to avoid certain medications beforehand.

What can I expect during a blood test?

Collecting a sample for a blood test takes only a few minutes. In an office, clinic, lab or hospital, your healthcare provider will:

  1. Wrap a tight band around your upper arm.
  2. Clean part of your skin inside of your elbow area.
  3. Insert a needle into that area, which may cause a stinging or pinching feeling.
  4. Attach a tube to the needle and fill the tube with blood.
  5. Remove the band and the needle.
  6. Put pressure on the puncture wound to help stop any bleeding.
  7. Place a bandage on your skin.

What should I expect after a blood test?

After a blood test, you should keep the bandage on for a few hours. You may also need to avoid exercise for a few hours afterward.

What are the risks of blood testing for cancer?

Blood tests are very safe and involve little risk. You may have a small bruise where the needle went into your skin. Rarely, the vein may swell, and warm compresses can help.

Results and Follow-Up

When should I know the results of my cancer blood tests?

Many blood test results are ready within a day or two, but others take several days to a week.

Your healthcare provider will let you know when to expect your results and discuss them with you at an appointment.

A note from Cleveland Clinic

Blood tests can provide important information about your overall health, organ function and potential diseases. If you’re having a blood test for cancer, ask your healthcare provider what’s being tested and why. The results will be considered with several other factors, including symptoms and additional tests.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 02/01/2022.

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