No routine blood test can rule cancer in or out. Tumour markers such as PSA, CA125 and CEA are not screening tests for the general population: they can be raised when there is no cancer and normal when there is. Doctors use them to help diagnose and monitor cancer alongside other tests. If you have a symptom that worries you, the right next step is your GP, not a blood test you buy online.
Sources: NHS, Cancer Research UK, the UK National Screening Committee and UCL (NHS-Galleri trial), all checked November 2026. Written by James Smillie, founder of TrueVitals, a blood testing company: see our bias statement below.
The NHS lists these as possible signs of cancer that you should get checked by a GP. Most turn out to be something less serious, but do not wait for, or rely on, a private blood test result.
If your GP thinks your symptoms could be cancer, you may get an urgent referral for tests or to see a specialist. If you feel very unwell, contact NHS 111, or call 999 in an emergency. A normal blood test, from us or anyone else, is never a reason to ignore a symptom.
Source: NHS, "Cancer: signs and symptoms" (nhs.uk/conditions/cancer/symptoms), reviewed May 2025, checked November 2026.
Tumour markers are substances, usually proteins, that may be raised in the blood when a cancer is present. Familiar examples are PSA (prostate-specific antigen) and CA125. Cancer Research UK explains that some tumour markers are also found in conditions that are not cancer, and some cancers do not produce a marker at all.
In hospital, doctors use tumour markers together with other tests to help diagnose a cancer, help plan treatment, see how well treatment is working and check whether a cancer has come back. That is where they are most useful: in someone who already has symptoms, a scan finding or a known diagnosis, so the result can be read in context.
What they are not designed for is answering the question "do I have cancer?" in a healthy person with no symptoms.
A screening test has to do two things well: find most cancers early, and not raise the alarm in lots of people who do not have cancer. Tumour markers struggle with both.
False positives. Cancer Research UK reports that around 72 to 80% of men with a raised PSA do not have prostate cancer. PSA can also rise after ejaculation, exercise or a urine infection, according to the NHS. CA125 can be raised by endometriosis, fibroids, pelvic inflammatory disease and pregnancy. A false alarm can mean anxiety, repeat tests and sometimes invasive investigations.
False negatives. Around 15% of men with a normal PSA level do have prostate cancer (Cancer Research UK). Some women with ovarian cancer have a normal CA125, and not all testicular cancers raise the markers AFP or hCG. A normal result is therefore not an all-clear.
Finding cancer earlier is not always the same as saving lives. The large UK ovarian cancer screening trial (UKCTOCS) used CA125. Cancer Research UK reports that it did detect cancers earlier, but this did not lead to saving lives, and the researchers concluded the tests could not be used to screen the general population. That is why there is no national screening programme for ovarian cancer.
Overdiagnosis. Some cancers found by testing would never have caused harm. Cancer Research UK describes overdiagnosis as the diagnosis of a cancer that would not have gone on to cause harm, which can lead to treatment, and side effects, that someone did not need. This is one of the main reasons the UK does not screen all men with PSA.
This is a general guide, not a diagnostic tool. Hospital teams choose which markers to test based on the person in front of them.
| Marker | Mainly linked with | What it is used for | Known limits |
|---|---|---|---|
| PSA (total, free, ratio) | Prostate | Investigating symptoms, informed-choice testing after a GP discussion, monitoring known prostate cancer | Most raised results are not cancer; can be raised by infection, ejaculation or exercise; can be normal with cancer |
| CA125 | Ovary | Investigating symptoms such as persistent bloating in women; monitoring known ovarian cancer | Raised by endometriosis, fibroids, pelvic inflammatory disease and pregnancy; can be normal with cancer |
| CEA | Often associated with bowel cancer, and others | With other tests in people with symptoms or a diagnosis; monitoring treatment and recurrence | Not specific to one cancer; can be raised in non-cancer conditions |
| CA 19-9 | Often associated with pancreatic and bile duct cancers | With imaging and other tests in people with symptoms, a finding or a diagnosis | Not specific; can be raised in non-cancer conditions |
| CA 15-3 | Often associated with breast cancer | With other tests in people with a diagnosis, for example to follow treatment | Not a breast screening test: NHS breast screening uses mammograms |
| AFP and hCG | Testicular (germ cell) and, for AFP, liver | With other tests to help diagnose testicular cancer, and throughout and after treatment | Not all testicular cancers raise them; other conditions can too |
Sources: Cancer Research UK pages on blood tests, ovarian cancer tests and testicular cancer tests; NHS PSA test page. Checked November 2026.
Screening on the NHS is done with tests that have been shown to do more good than harm in a whole population. In England, the adult cancer screening programmes are:
Prostate (PSA): informed choice, not routine screening. The NHS says routine PSA testing is not currently offered, but anyone with a prostate can ask a GP about it, and the doctor will discuss the benefits and risks before a decision is made. In May 2026 the UK National Screening Committee recommended targeted screening, a PSA test every 2 years, for men aged 45 to 61 with a BRCA2 gene change and a relevant family history. Cancer Research UK reports that the government accepted this for England in June 2026, with roll-out starting in 2027; Scotland, Wales and Northern Ireland are still considering it. Our PSA blood test guide covers the test in more detail.
If you are invited to any of these programmes, take it up. A private blood test is not a substitute for any of them.
Sources: NHS, "NHS screening" (reviewed July 2024) and "PSA test" (reviewed September 2024); Cancer Research UK, "Screening for prostate cancer" (reviewed June 2026). Checked November 2026.
Multi-cancer early detection (MCED) tests look for signals from tumour DNA in the blood and try to flag many cancer types from one sample. The best known is Galleri, made by GRAIL. They work differently from the tumour markers above, and they are still being evaluated.
What the NHS-Galleri trial found. More than 142,000 volunteers aged 50 to 77 in England gave three blood samples over two years. First results were published in June 2026. According to UCL, the main aim, a reduction in stage 3 and stage 4 cancers combined over three years, was not met: there was no overall difference in late-stage diagnoses. A pre-specified secondary measure did show more than a 20% reduction in stage 4 cancers, strengthening by the third year, and 25% fewer cancers were found in emergency settings such as A&E. Just over half of people with a positive Galleri result were diagnosed with cancer.
What happens next. Analysis continues, including whether yearly screening reduces deaths from cancer and the psychological impact of a positive result. The NHS and other health organisations are reviewing the results in detail. Galleri is not part of NHS screening.
What that means for you. An MCED test is a different thing from a general health blood test, and a negative result does not rule out cancer. If you are considering one privately, talk it through with your GP first, and keep doing your NHS screening.
Source: UCL News, "First results from the NHS-Galleri trial announced", 1 June 2026. Checked November 2026.
We include tumour markers in our larger panels, so we owe you a plain explanation of what they mean. These lists come from our Ultimate panel and Signature panel pages.
What they can do. Give you, and your GP, a baseline. Flag a value that is outside the laboratory range so that it can be discussed, repeated or investigated. Your clinician-reviewed report reads each marker alongside your other results and your own lifestyle quiz, and anything raised is flagged with advice to follow up with your GP.
What they cannot do. They cannot tell you that you have cancer, and they cannot tell you that you do not. A normal result is not an all-clear, and a raised result is usually not cancer. Our tests are not a cancer screening test and should not replace NHS screening, a GP appointment or an urgent referral.
Know what you are signing up for. If you would rather not receive a tumour marker result that may need follow-up, or you would find a borderline result distressing, think about that before you book. It is a fair reason to choose a smaller panel.
If you have symptoms, see your GP. They can examine you, order the right tests and refer you urgently if needed. A panel bought online cannot do that, and waiting for one can delay the help you need.
If your main worry is cancer and you have no symptoms, a general health panel is not the tool for that job. Take up your NHS screening invitations, and talk to your GP about your personal risk.
If cancer runs in your family, for example several close relatives with breast, ovarian, bowel or prostate cancer, or a known BRCA gene change, ask your GP whether you should be referred for genetic assessment or enhanced screening. That is far more useful than a tumour marker.
If you are being treated or monitored for cancer, use your hospital team's tests. They compare results over time in the same laboratory, which matters for tumour markers.
Where a private panel can help is as a broad health check (heart, metabolic, liver, kidney, hormones, nutrients and more) for people who understand that the tumour markers in it are context, not a verdict. If you feel unwell and your NHS results came back normal, our guide to feeling unwell with a normal blood test may help, and our list of blood tests to ask your GP for is a good starting point.
TrueVitals is a UK blood testing company and some of our panels include tumour markers, so we have an interest in this topic; we compare ourselves too. This page was written on 2 November 2026 using only sources we opened that day or that month: NHS pages on cancer symptoms, NHS screening and the PSA test; Cancer Research UK pages on blood tests, ovarian cancer screening and tests, testicular cancer tests and prostate cancer screening; and UCL's report of the NHS-Galleri trial results. It is general information, not medical advice, and it is not a diagnosis. Written by James Smillie; reviewed by the TrueVitals clinical review team.
Ultimate: 140 biomarkers (139 for women), £399 including your blood draw, clinician-reviewed report within 4 working days. Not a cancer test: anything raised is flagged for your GP.
Not sure? Take the free quiz: answer a few questions about you and see which markers are worth checking.
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