Can High ESR and CRP Levels Indicate Cancer?

A raised ESR or CRP can be a sign of cancer, but these tests only show that the body is inflamed somewhere, not why. Most people with a high result turn out to have something far more ordinary, such as an infection or a flare of a long-term condition. For doctors, these results work like a clue that points toward looking further, not a verdict.¹

What ESR and CRP Actually Measure

Doctors often group these two tests as inflammatory markers, meaning blood measurements that rise when the body is inflamed. CRP (C-reactive protein) is a protein the liver releases into the blood within hours of inflammation starting. ESR (erythrocyte sedimentation rate) measures how fast red blood cells sink to the bottom of a tube over an hour, reported in millimetres per hour. During inflammation, a clotting protein in the blood rises and makes red cells stick together in stacks that sink faster.² Because of how it works, ESR changes more slowly than CRP, both on the way up and on the way down. Both tests run on a routine blood draw, so you don’t need a special appointment.

Your doctor probably ordered them as cheap first-line tests for vague symptoms such as tiredness, weight loss or aches, usually when infection or inflammation is a possibility and no simpler test gives an answer. They often come bundled with a blood count, liver tests and calcium.

On your report, CRP is usually given in mg/L, and normal is typically under about 5 to 10 depending on the lab. ESR ranges vary with age and sex, so check the range printed beside your result. A result just above the line means something very different from a reading in the hundreds.

Some cancers set off an inflammatory response, and a hidden cancer can push CRP up before anyone knows it is there.³ Inflammation itself may also raise cancer risk, so a high level does not show which came first.⁴ Neither test can say which organ is inflamed or whether the cause is infection, autoimmune disease or a tumour. That is why doctors pair the result with your symptoms, an examination and other tests.

How Likely Cancer Is After a Raised Result

Among family-practice patients with a raised inflammation test, about 3.5 in 100 are diagnosed with cancer within the following year.⁵ For comparison, the figure is about 1.5 in 100 among people whose tests came back normal, and about 1 in 100 among people who were never tested.⁶ A raised result roughly doubles the short-term chance, but from a low starting point.

The figure comes from people already seeing a doctor, often with symptoms, so it may overstate the odds for a healthy person. The one-year window counts cancers found soon after the test, which includes some that were already present and causing the result. Many of those who are not diagnosed will still have a real cause, such as an infection or a flare of a long-term condition.

The odds are higher with higher readings, in older people, and in men.⁷ Age matters in two ways. Cancer is more common with age to begin with, so a 30-year-old and a 75-year-old with the same reading face different odds. ESR also rises naturally as people get older, which makes older people’s readings harder to interpret.

The odds rise further if a repeat test is still abnormal, and fall if it returns to normal.⁸ Waiting a few weeks lets a short-lived cause such as a recent infection settle, so a repeat separates a passing blip from a persistent rise. A result that stays high usually leads the doctor to look for a cause.

Common Non-Cancer Causes of High ESR and CRP

Kidney disease, being female and getting older all raise ESR on their own.⁹ Anaemia can speed up how quickly red cells settle, so ESR can be raised by conditions that aren’t really inflammation.

In people with no known inflammatory illness, body weight is the main thing driving CRP levels up.¹⁰ Fat tissue releases inflammatory signals that prompt the liver to make more CRP, so people carrying extra weight often have a constantly higher baseline. It is a modest, steady rise rather than the sharp spikes seen with infection, and it doesn’t mean something is acutely wrong, though it is still worth knowing about for long-term health. In that same group, older age is the main reason ESR runs high while CRP stays normal.¹¹

Short-term events matter too. A recent cold, flu, chest or urinary infection can raise CRP for days to weeks. So can recent surgery, an injury or a dental infection. Flares of arthritis, lupus or bowel disease raise both tests. Tell your doctor about any recent illness before you read too much into a result.

When ESR is extremely high, infection is the most common cause, at about a third of cases.¹² Cancer comes a close second, at just under a third, with kidney disease, rheumatic disease and unexplained cases making up the rest.¹³ An extremely high ESR calls for a proper search for the cause, even though infection remains the likelier answer.

When a Very High Reading Matters More

In family practice, about 14 in 100 people with an ESR of 100 or more are diagnosed with cancer within a year.¹⁴ With a CRP of 100 mg/L or more, it is about 7 in 100.¹⁵ Even at these levels most people do not have cancer, but these readings are worth chasing. A very high CRP with vague symptoms should prompt scans to look for infection or cancer, even in someone who already has a rheumatic condition.¹⁶ An ESR in the triple digits is rarely explained by age alone, and a high reading without any clear infection is the pattern doctors watch most closely.

Your doctor will usually start with a careful history and examination, looking for signs of infection, joint disease or lumps. Further blood tests and a urine test are common early steps, and imaging is considered if the cause is still unclear. The order depends on your symptoms: chest symptoms may lead to a chest X-ray, while bone pain may lead to blood or urine tests for abnormal proteins.

Some symptoms should go to your doctor along with a high result: unexplained weight loss, night sweats or an ongoing fever; new bone or back pain that doesn’t settle; lasting tiredness, breathlessness, or a cough that won’t go away. Mention any of these even if they seem minor.

Cancers Most Linked to High ESR and CRP

Multiple myeloma is a cancer of the plasma cells in the bone marrow. In the year before diagnosis, about 85 in 100 people with myeloma had an abnormal ESR, compared with 46 in 100 people without it.¹⁷ Only 46 in 100 had an abnormal CRP, close to the 37 in 100 seen in people without myeloma.¹⁸ ESR is the more useful of the two for spotting myeloma, while CRP adds little.¹⁹

The reason is that myeloma cells make large amounts of abnormal antibody proteins, and these extra proteins make red cells clump and sink faster. The cause isn’t classic inflammation, so ESR can be strikingly high even when CRP is normal. That is also why ESR is the test that sometimes first raises the question. Doctors then look for bone pain, anaemia, high calcium and kidney problems, and a simple blood or urine test for abnormal proteins can check for it. A high ESR alone does not mean myeloma.

In healthy people, a CRP above 3 mg/L is linked to about double the risk of later lung cancer compared with a CRP below 1.²⁰ The link with bowel cancer is weaker and less certain, and no link was found for breast cancer.²¹ In people with inflammatory bowel disease, higher CRP and ESR go with a higher risk of bowel cancer.²²

The lung cancer finding comes from following healthy people over time, so it shows a statistical link across groups rather than a prediction for you. Smoking drives both raised CRP and lung cancer, which makes the two effects hard to separate, and CRP is not used as a screening test for lung or bowel cancer in healthy people.

Why a Normal Result Does Not Rule Cancer Out

Among people in family practice who went on to be diagnosed with cancer, fewer than half had a raised CRP or ESR beforehand.²³ These tests cannot be used to rule cancer out.²⁴ Many early or small tumours cause little inflammation, and some cancer types simply don’t raise these markers. Scans, endoscopy and specific blood tests look for things ESR and CRP cannot detect.

Go back to your doctor if a symptom lasts more than a few weeks, and ask whether other tests, such as a scan or targeted bloodwork, fit what you’re feeling. Keep a note of when symptoms started and how they have changed.

When ESR and CRP Disagree

About 1 in 8 hospital adults tested for both got results pointing in opposite directions.²⁵ A high CRP with a normal ESR more often points to an infection such as a urinary, lung or gut infection.²⁶ A high ESR with a normal CRP more often points to lupus-type conditions, bone and joint infections, or recent stroke.²⁷ Outside hospital, a high ESR with normal CRP is mostly linked to age, and a high CRP with normal ESR mostly to body weight.²⁸

A split result doesn’t mean one test is wrong; the two respond to different processes and at different speeds. CRP rises and falls within days, while ESR lags behind. Early in an infection, CRP can be high before ESR catches up, and after recovery ESR can stay raised for weeks after CRP is normal. Doctors treat the pattern as a pointer toward likely causes. If your results disagree, you could ask which one your doctor is more interested in and why, whether timing or a recent illness explains the gap, and when the tests should be repeated.

What Happens After a High Result

Doctors treat these markers as clues to be combined with other routine tests and your symptoms.²⁹ A repeat test often follows.³⁰ Expect questions about recent infections, pain, weight changes and other symptoms. A physical examination may include checking your lymph nodes, abdomen, joints and blood pressure. Your doctor may also ask about family history, smoking and medicines, since these shape which causes are most likely, and will usually explain whether they plan to wait and repeat the test or investigate straight away.

If you already have cancer, ESR and CRP may be tracked over time, since higher levels tend to go with a harder course.³¹

Before the appointment, write down any recent colds, infections, injuries or dental problems, and list your symptoms with when they began. Bring your medicine list. Anti-inflammatory painkillers and steroids can lower inflammation tests, which may make a true problem look smaller than it is, so tell your doctor which you take and whether you took them before the blood draw. Don’t stop prescribed medicine to prepare for a repeat unless your doctor tells you to.

Further tests depend on the picture. More bloodwork may check blood counts, kidney and liver function, and calcium. Urine or blood protein tests may be used if myeloma is a question. Scans are usually reserved for very high or persistent results, especially with symptoms.