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.
Blood testing is one of many tools healthcare providers use to diagnose and manage cancer. The tests can provide important information about:
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Blood tests for cancer fall into four general categories:
Although blood tests are useful in cancer diagnosis, they’re not used by themselves. Other tests are almost always necessary, including:
Blood tests can be useful in all types of cancer, particularly blood cancers such as:
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.
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:
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.
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.
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.
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.
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.
Collecting a sample for a blood test takes only a few minutes. In an office, clinic, lab or hospital, your healthcare provider will:
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.
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.
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.
Last reviewed by a Cleveland Clinic medical professional on 02/01/2022.
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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy