Repeat or extend testing
A clinician may repeat the result, order a more specific blood test or examine a blood smear to determine whether the pattern persists.
Evidence-led blood test guide
Can a Blood Test Detect Cancer? What Tumor Markers and Routine Blood Tests Show
A practical guide to routine blood work, cancer markers, CRP, confirmatory testing and newer blood-based approaches.
Start with routine blood workHLI editorial team
Evidence reviewed by the editorial team. A named clinician was not supplied, so no medical reviewer is represented in the page schema.
The answer first
A blood test can detect some cancers, but most routine blood tests cannot. A complete blood count can flag blood cancers such as leukemia, and tumor marker tests help diagnose or monitor specific cancers. The National Cancer Institute reports that circulating tumor markers have generally not worked well for screening. Galleri® is a different, newer kind of blood test. Galleri is under FDA review and is not FDA-approved.
FDA status checked 6 Oct 2026: GRAIL filed its premarket approval application on 29 Jan 2026; an FDA advisory panel voted favorably on 23 Sep 2026 (7–2 on benefit versus risk, 6–4 on effectiveness). The vote is non-binding and no FDA decision has been issued. See the current Galleri FDA status.
Human Longevity sells the Galleri test.
What routine panels reveal
Can a Routine Blood Test Detect Cancer?
A routine blood test, such as a complete blood count or metabolic panel, usually cannot detect cancer. Cleveland Clinic states that blood work alone cannot detect most cancers, with blood cancers among the exceptions. A normal result does not rule cancer out, and most abnormal blood results have non-cancerous causes.
| Routine test or finding | What it can flag | What it does not show |
|---|---|---|
| Complete blood count | Unusual red-cell, white-cell or platelet patterns that can prompt evaluation for leukemia, lymphoma or myeloma. | It does not directly detect most solid tumors, including lung, breast and colon cancer. |
| Metabolic panel | Changes in organ function or electrolytes that may need follow-up for many possible causes. | It cannot identify cancer or establish why a value is abnormal. |
| Indirect clues | A raised red-cell count can prompt a doctor to consider kidney cancer among many more common explanations, according to MD Anderson. | An indirect clue is not a cancer diagnosis and is not specific to one disease. |
| Lipid panel | Cholesterol and triglycerides used in cardiovascular risk assessment. | Cleveland Clinic notes that a lipid panel does not check for cancer. |
City of Hope notes that leukemia may sometimes be diagnosed from blood when leukemia cells have moved from bone marrow into circulation. Even then, blood smear, flow cytometry and bone marrow testing may be needed. A normal routine panel does not mean that no cancer is present.
Proteins and other measurable substances
What Are Tumor Markers, and Which Cancer Markers Show Up in a Blood Test?
A tumor marker is a substance made by cancer cells, or by the body in response to cancer, that can be measured in blood, urine or tissue. Common blood markers include PSA, CA-125, CEA, AFP and CA 19-9. NCI notes that many cancers have no known marker and non-cancerous conditions can raise the same markers.
| Marker | Usually linked to | Sample |
|---|---|---|
| PSA | Prostate cancer | Blood |
| CA-125 | Ovarian cancer; read more about ovarian cancer and the Galleri test | Blood |
| CEA | Colon, pancreatic and other cancers; see colon cancer and blood tests | Blood |
| AFP | Liver cancer, ovarian cancer and germ-cell tumors | Blood |
| CA 19-9 | Pancreatic, gallbladder, bile duct and stomach cancers; see pancreatic cancer and the Galleri test | Blood |
| CA 15-3 / CA 27.29 | Breast cancer | Blood |
| hCG | Germ-cell tumors | Blood or urine |
| LDH | Leukemia, lymphoma, melanoma and other cancers | Blood |
| Calcitonin | Medullary thyroid cancer | Blood |
| Beta-2-microglobulin | Myeloma, chronic lymphocytic leukemia and some lymphomas | Blood, urine or cerebrospinal fluid |
NCI distinguishes circulating markers—measured in blood, urine, stool or bone marrow—from tissue markers measured in a tumor. Gene-based markers such as BRCA or BRAF can guide inherited-risk assessment or treatment selection; they are not tumor-marker evidence that cancer is present.
Purpose matters more than the name
Cancer Marker Blood Tests by Purpose: Screening, Diagnosis, Staging and Monitoring
Most cancer marker blood tests are used after cancer is diagnosed to stage it, guide treatment, check response or watch for recurrence. MedlinePlus says tumor marker tests have a limited screening role. PSA is the best-known exception: the USPSTF 2018 recommendation makes screening an individual decision for men 55 to 69.
| Marker | Clinical purpose described by NCI | Average-risk screening role |
|---|---|---|
| AFP | Help diagnose liver cancer and germ-cell tumors; follow treatment. | No routine screening role. |
| CA 19-9 | Assess whether treatment is working. | No routine screening role. |
| CA-125 | Support diagnosis, treatment-response assessment and recurrence monitoring. | No routine screening role. |
| CA 15-3 / CA 27.29 | Assess treatment response, recurrence and metastasis. | No routine screening role. |
| Beta-2-microglobulin | Estimate prognosis and follow treatment. | No routine screening role. |
| Beta-hCG | Support staging, prognosis and response assessment. | No routine screening role. |
| PSA | Support prostate evaluation and follow known prostate cancer. | USPSTF 2018: individual decision for men 55–69 (Grade C); recommends against for men 70+ (Grade D). An update is in progress. |
NCI explains the screening problem plainly: circulating markers can miss people who have cancer and flag people who do not. Studies have generally not shown them to be sensitive and specific enough for population screening.
A result is context, not a verdict
What Does a High or Normal Cancer Marker Result Mean?
A high tumor marker result means the value is above that laboratory's reference range; it does not mean cancer. Non-cancerous conditions, medications and procedures can raise markers, while some people with cancer have normal levels. Each marker has its own range, so the marker, laboratory and trend over time all matter.
A “tumor marker of 400” means nothing on its own because different markers use different units and ranges. CA-125 can rise with endometriosis, according to MD Anderson. Cleveland Clinic also lists medications, procedures, stress and some foods as possible influences on results.
Blood Cancer United notes that about 1 in 20 healthy people falls outside the reference range on a given blood test. A single high result often has a benign explanation. Contact the ordering clinician rather than self-interpreting or self-ordering a marker panel.
Timing and next steps
Cleveland Clinic says routine blood results often return in a day or two, while biopsy results may take a week or longer. Repeat testing and the direction of change can be more useful than one isolated value. A biopsy is usually needed to diagnose or rule out cancer.
Inflammation is not a cancer signal
Does a CRP Blood Test Detect Cancer?
No. A C-reactive protein blood test measures inflammation, and MedlinePlus states that the result shows neither what is causing the inflammation nor where it is. CRP is not on NCI's list of tumor markers in common use. Infections, autoimmune diseases and other conditions can raise CRP, so it cannot confirm or rule out cancer.
Research has examined associations between CRP and cancer risk, but an association is not a diagnostic test. High-sensitivity CRP has a different use: it may be used in cardiovascular risk assessment.
From clue to diagnosis
What Confirms Cancer After an Abnormal Blood Test?
A biopsy, in which a tissue sample is examined under a microscope, is the standard way to confirm cancer. MD Anderson states that no single blood test can say with certainty that a person has cancer. A doctor combines the blood result with examination, imaging and sometimes bone marrow testing.
Locate the cause
Imaging can look for a structural explanation. For a suspected blood cancer, flow cytometry can characterize abnormal cells.
Confirm with tissue
A tissue or bone marrow biopsy can establish a diagnosis. Liquid biopsies are used mainly to characterize or monitor known cancer, not to diagnose it alone.
A newer category with different limits
Is There a Blood Test That Looks for Many Cancers at Once?
An MCED test analyzes cell-free DNA for a shared cancer signal in people who have no diagnosis. Galleri, made by GRAIL, is one. It is under FDA review and is not FDA-approved. PATHFINDER 2 prospectively followed 35,878 adults.
39.3%Sensitivity across all cancers diagnosed within one year in PATHFINDER 2 full results
69.8%Sensitivity for GRAIL's pre-specified group of 12 in PATHFINDER 2
99.6%Specificity in PATHFINDER 2; positive predictive value was 60.3%
Cancer signal origin accuracy was 91.3% in the PATHFINDER 2 full results reported by GRAIL at ASCO on 31 May 2026 and published in Nature Medicine on 22 Sep 2026. NHS-Galleri results were mixed: the 142,250-participant study did not meet its primary endpoint of reducing Stage III–IV diagnoses.
| Question | Routine panel | Tumor marker | MCED test |
|---|---|---|---|
| What it measures | Blood counts or chemistry | A protein or other substance against a reference range | Cancer-associated patterns in cell-free DNA |
| Usual role | General health assessment and clues that prompt workup | Mostly diagnosis support, treatment response or recurrence monitoring | Look for a shared cancer signal in adults without a diagnosis |
| Meaning of a normal result | Does not rule cancer out | Does not rule cancer out | “No Cancer Signal Detected” does not rule cancer out |
| Meaning of an abnormal result | Needs clinical interpretation | Needs clinical interpretation and possibly workup | “Cancer Signal Detected” requires diagnostic workup |
| Screening status | Not a population cancer screen | Generally not used for average-risk screening; PSA is a limited exception | Does not replace guideline screening; no USPSTF, ACS or NCCN endorsement |
What does “50+ cancer types” mean?
Galleri's “50+” language refers to cancer types observed in study participants when a signal was detected; it is not a claim of demonstrated performance for every listed cancer. Galleri states that it does not detect a signal for all cancers. Evidence is strongest for GRAIL's pre-specified group of 12: anus, bladder, colorectal, esophagus, head and neck, liver/bile duct, lung, lymphoma, myeloma/plasma cell neoplasm, ovary, pancreas and stomach. PATHFINDER 2 sensitivity across all cancers was 39.3%.
NCI says multi-cancer detection tests are still being studied and a key question is whether treating cancers they find reduces deaths. Galleri is prescription-only and costs $798 through Human Longevity. It is not covered by Medicare. The Nancy Gardner Sewell Medicare MCED Screening Coverage Act allows possible coverage of FDA-approved tests from 2028 at the earliest, but Galleri would first need FDA approval and a CMS decision. See Galleri cost and coverage and the cancers evidence overview.
Human Longevity sells Galleri and does not sell Cancerguard. Exact Sciences' Cancerguard site, retrieved 6 Oct 2026, states that its prescription-only laboratory-developed test is not FDA cleared or approved.
Match the test to the question
Which Blood Test Makes Sense for Your Situation?
The right blood test depends on the situation. Adults without symptoms follow guideline screening. Doctors may order blood counts or markers when evaluating an abnormal finding or known risk, and markers are often used after diagnosis. A multi-cancer test is an addition to guideline screening, not a replacement.
| Situation | Usual approach | Who guides it | Important note |
|---|---|---|---|
| No symptoms, average risk | Age- and risk-appropriate guideline screening | Primary care clinician | Routine blood work is not a substitute. |
| A concerning finding | Targeted blood tests, examination and imaging | Clinician evaluating the finding | Do not self-order marker panels. |
| Strong family history | Risk assessment and genetic counseling | Genetic counselor or specialist | Inherited risk and current cancer signals are different questions. |
| Already diagnosed | Disease-specific markers when clinically useful | Oncology team | Markers may help monitor treatment or recurrence. |
| Interested in a multi-cancer blood test | Discuss potential benefits, limits and follow-up with a physician | Prescribing clinician | Galleri remains supplemental to guideline screening. |
A different question on a different timeline
Do Blood Tests Show Inherited Cancer Risk?
Tumor markers, routine blood counts and Galleri do not report inherited cancer risk. GRAIL states that Galleri does not predict future genetic risk. Inherited risk is assessed from a person's DNA by genetic testing, which is generally done once; whole genome sequencing does not detect cancer that is already present.
| Approach | Question it can help answer | Timing |
|---|---|---|
| Routine tests, markers and Galleri | Is there an abnormality or signal in the blood now? | Repeated when a clinician orders it |
| Genetic testing or a genome | Which inherited variants does a person carry? | Generally performed once |
People with a family history of breast or ovarian cancer can ask about BRCA1 and BRCA2 testing. A family history of colorectal or endometrial cancer may warrant discussion of Lynch syndrome. A genetic counselor can help choose the appropriate test and interpret results. Human Longevity sells both Galleri and a genome service, but they answer different questions.
Clear answers
Frequently Asked Questions
Can a blood test detect all cancers?
No. Blood counts can flag some blood cancers, and tumor markers can help with specific cancers, mostly after diagnosis. Most solid tumors do not show up on routine blood work, and Galleri does not detect a signal for all cancers.
What is the best blood test to detect cancer?
There is no single best blood test. The appropriate test depends on whether someone has symptoms, a known diagnosis, inherited risk or no symptoms at all. Guideline screening remains the starting point for adults without symptoms.
What are the most common tumor markers?
Common blood tumor markers include PSA, CA-125, CEA, AFP and CA 19-9. Each is associated with particular cancers and clinical purposes, but none can diagnose cancer by itself.
What is a normal range for cancer markers?
Each marker has its own reference range, and ranges can vary by laboratory. The range printed with the result, the reason for testing and the trend over time all matter.
What does a tumor marker of 400 mean?
Nothing by itself. Different markers use different units and reference ranges, so a value of 400 cannot be interpreted without knowing the marker, laboratory, clinical context and prior results.
Does cancer show up in routine blood work?
Usually not. A complete blood count can reveal patterns associated with leukemia and other blood cancers, but a normal blood panel does not rule out cancer and a CBC does not detect most solid tumors.
Which cancers do not show up on routine blood tests?
Most solid tumors, including lung, breast and colon cancer, do not appear directly on a routine complete blood count. This is one reason guideline screening tests remain necessary.
Is CRP a tumor marker?
No. CRP measures inflammation. It cannot show what is causing inflammation, where it is occurring, or whether cancer is present.
If my blood tests are normal, can I still have cancer?
Yes. Normal routine blood work and normal tumor marker levels do not rule cancer out. A doctor considers the result alongside history, examination, imaging and, when needed, biopsy.
What 50 types of cancer can be detected by a blood test?
Galleri’s “50+” language refers to cancer types observed in study participants when a signal was detected, not proven performance for every listed cancer. In PATHFINDER 2, sensitivity across all cancers was 39.3%.
Is the Galleri test FDA-approved?
No. Galleri is under FDA review and is not FDA-approved. As of October 6, 2026, an advisory panel vote had occurred, but no FDA decision had been issued.
Should I worry about an elevated tumor marker?
Do not interpret the number alone. Many non-cancerous conditions can raise tumor markers. Contact the clinician who ordered the test; repeat testing and the trend over time may be more informative than one result.
Sources and Evidence Notes
Sources were selected from government health agencies, prospective studies and medically reviewed clinical references. Regulatory and study-status claims were checked against the brief on October 6, 2026.
- National Cancer Institute — Tumor Markers
- National Cancer Institute — Tumor Marker Tests in Common Use
- MedlinePlus — Tumor Marker Tests
- MedlinePlus — C-Reactive Protein Test
- USPSTF — Prostate Cancer Screening (2018)
- GRAIL — PATHFINDER 2 full results, ASCO, 31 May 2026
- Nature Medicine — PATHFINDER 2, 22 Sep 2026, NCT05155605
- Nature Medicine — NHS-Galleri, 22 Sep 2026, NCT05611632
- Galleri — Important Safety Information
- Congress.gov — H.R.842
- Cleveland Clinic — Blood Tests for Cancer, updated 6 May 2024
- Cleveland Clinic — Tumor Marker Tests, updated 4 May 2026
- MD Anderson — Which blood tests show cancer?, 19 May 2025
- City of Hope — Blood Test for Cancer, 12 Jun 2024
- Blood Cancer United — Understanding reference ranges, read 6 Oct 2026