What a Positive Cancer Blood Test Result Means

By Dr. Diana Rangaves, PharmD

Positive cancer blood test results, such as elevated tumor markers or abnormal cell counts, don’t necessarily mean you have cancer. It simply indicates something unusual that may need further investigation. ^[1]

Blood tests alone can’t diagnose cancer, so healthcare providers often follow up with cancer diagnosis tests like imaging (CT, MRI, PET), biopsies, or more blood work to confirm what’s going on.^[1]

If you’ve received a positive result, you’re not alone. Here, we’ll break down what CBC positive cancer blood test results might indicate, why further testing is essential, and what steps to take next for your health and peace of mind.

What Blood Tests Can Reveal

While blood tests can’t diagnose cancer on their own, they can pick up on abnormalities that warrant further testing:

Complete Blood Count (CBC)

CBC tests measure the levels of different blood cells, including the red blood cells, white blood cells, and platelets ^[2]. Irregularities in these blood counts may point to various health concerns.

For example, a low red blood cell count may suggest anemia, which can sometimes be associated with cancers such as colon cancer.^[1] Very high or very low white blood cell levels may indicate leukemia or other disorders involving the bone marrow.^[1]

Tumor Marker Tests

Tumor markers are substances, often proteins, produced by cancer cells or by the body in response to cancer.^[3] Elevated levels may raise suspicion for cancer, but they are not definitive, as non-cancerous conditions can also cause these levels to rise.^[5]

Common examples include PSA (prostate-specific antigen) for prostate cancer, CA-125 for ovarian cancer, CEA (carcinoembryonic antigen) for colorectal and other cancers, and AFP (alpha-fetoprotein) for liver cancer.^[4] Not all cancers produce detectable tumor markers, and not all elevated markers indicate cancer.^[5]

Blood Protein Testing

This test assesses the presence and levels of specific proteins in the blood, including immunoglobulins. One commonly used method, called electrophoresis, can detect abnormal proteins known as M-proteins, which are often associated with multiple myeloma and occasionally with lymphoma.^[1] These findings can help guide further diagnostic steps.

Circulating Tumor Cells (CTCs)

These advanced tests detect fragments of tumor cells that circulate in the bloodstream.^[1] Although they are primarily used to monitor existing cancers and evaluate cancer treatment response, ongoing research is exploring their potential for earlier detection and broader clinical use.

What a “Positive” Result Actually Means

Getting a “positive” result on a cancer-related blood test can sound alarming. Yet in this context, it simply means that something abnormal was detected. That could be an elevated tumor marker, an unusual blood cell count, or an irregular protein level.^[1] None of them confirms blood cancer on their own.

These results often act as early signals, prompting further investigation. Sometimes, false positives can happen, especially with tumor markers like CA-125 or PSA, which can rise for reasons unrelated to cancer.^[6]

Next Steps After a Positive Blood Test

If you’ve received a positive or abnormal result from a cancer-related blood test, the next steps are important. While it’s completely natural to feel anxious, keep in mind that this result is often just the beginning of a larger diagnostic process, not a conclusion.

1. Schedule a Follow-Up Appointment

Your first move should be to talk with your healthcare provider. They will explain the results, place them in the context of your medical history, consider possible non-cancer causes, and recommend any necessary next steps.

2. Repeat the Blood Test (If Advised)

Sometimes, abnormalities appear due to lab errors, temporary illnesses, or other non-serious factors. Your healthcare provider might suggest repeating the test after a short interval to confirm whether the results are consistent.

3. Undergo Imaging Tests

If the concern persists, imaging studies like CT scans, MRIs, ultrasounds, or PET scans may be ordered to check for tumors or other internal abnormalities. These tests help assess the size, shape, and location of anything unusual.^[7]

4. Receive a Biopsy

A biopsy, where a small tissue sample is taken and examined under a microscope, is often used to confirm or rule out cancer. The type of biopsy depends on the suspected area, such as needle, surgical, or endoscopic.^[8]

5. Referral to a Specialist

Depending on the findings, your healthcare providers may refer you to a specialist such as an oncologist, hematologist, or radiologist for further evaluation and care planning.

6. Monitor Symptoms and Lifestyle Factors

While tests are underway, keep track of any changes in your body, such as fatigue, weight loss, or new lumps, and inform your healthcare provider. Lifestyle choices like smoking, alcohol use, and stress can also influence results, so they may be part of the conversation too.

When to and When Not to Worry

A positive cancer-related blood test can be unsettling, but not every abnormal result points to something serious. Knowing when to act and when to stay calm can help you respond wisely.

When to Be Concerned

Take it more seriously if:

• You have ongoing symptoms like unexplained weight loss, fatigue, new lumps, or unusual bleeding^[9]
• Multiple blood tests show abnormalities (eg, high tumor markers and low red blood cells)^[9]
• You have a personal or family history of cancer^[9]
• Your healthcare provider recommends further testing or specialist care

When Not to Panic

Sometimes, results are abnormal but not alarming:

• Mild or borderline changes could be due to infection, stress, or even menstruation
• You have no symptoms and feel well overall
• Your results are just outside the normal range and stabilize over time
• Similar results in the past turned out to be harmless

Take the Next Step With Confidence

A positive cancer blood test result doesn’t mean you have cancer. It means further steps are needed. While it can be alarming, it’s often just the beginning of a deeper investigation, not a final answer.

If you want to stay proactive about your health, Everlywell offers an easy at-home lab test for colon cancer and an in-person test for multi-cancer detection.