CA 19-9 is a substance made by cells of the pancreas, bile ducts, stomach and bowel, and in some cancers, especially pancreatic and bile duct cancer, its level in the blood rises [1, 3]. The usual upper limit is 37 units per millilitre [2]. A high level does not show cancer on its own: a blocked bile duct and jaundice, inflammation of the pancreas, poorly controlled diabetes and liver disease can also raise it [2, 3]. The main job of this test is to follow treatment in people whose cancer has already been diagnosed, not to check healthy people [2, 5].
Key points
- CA 19-9 is not suitable for finding cancer in healthy people: in a study of about 71,000 people without symptoms, fewer than 1 in every 100 people with a high CA 19-9 had pancreatic cancer [3].
- A blocked bile duct and jaundice are among the most important causes of a "false" high result; the doctor usually repeats the test once the duct has been opened [2, 4].
- About 1 in every 10 to 20 people make no CA 19-9 because of an inherited feature of their blood group [2]; in some populations this number is higher [3]. In these people the test is usually normal even when cancer is present [2, 3].
- In pancreatic cancer, a fall in CA 19-9 with treatment is a good sign, and a rise over several tests in a row may be a sign that the disease is growing; but this must be confirmed with scans [2, 5].
What is CA 19-9 and what is it tested for?
CA 19-9 is a substance on the surface of cells, made by the cells of the pancreatic and bile ducts and by the lining of the stomach, bowel, womb and salivary glands [3]. Among cancers it rises most often in pancreatic cancer, but it can also be raised in cancer of the gallbladder and bile ducts, stomach, liver, bowel and several other cancers [1, 3].
This test has two main uses [1, 2, 4]:
- Following treatment: in people who have cancer of the pancreas, gallbladder, bile ducts or stomach, it shows whether treatment is working.
- Helping with the diagnosis in someone who has symptoms: always together with scans and a biopsy, never on its own.
Read about tumour markers in general: What is a tumour marker?
What should CA 19-9 be? (normal range)
In most laboratories, the upper limit of normal for CA 19-9 is about 37 units per millilitre [2, 3]. Compare your number with the range printed on your lab report.
- A slightly raised CA 19-9 in someone with no sign of cancer or of pancreatic or bile duct disease is common and has many harmless causes [3].
- The higher the number, and the longer it stays high in later tests, the more further checks are needed [3].
- In people who have pancreatic cancer, a very high number often means more widespread disease [2, 3].
What besides cancer can raise CA 19-9?
| Cause | Explanation |
|---|---|
| A blocked bile duct and jaundice, for example from a stone in the bile duct | An important cause of falsely high results; it usually falls once the duct is opened, and the test should then be repeated [2, 3, 4] |
| Infection of the bile ducts (cholangitis) | Can raise the number a great deal; after treatment it usually returns to normal within about two months [3] |
| Inflammation of the pancreas (pancreatitis) and pancreatic cysts | CA 19-9 is raised in some of these patients, and the test alone cannot tell them apart from cancer [3] |
| Diabetes, especially when blood sugar is high and poorly controlled | High blood sugar itself raises CA 19-9 [3] |
| Liver disease: hepatitis and cirrhosis | The more severe the liver damage, the higher the CA 19-9 [3] |
| Diseases of the lungs and airways, and some harmless gynaecological and urinary conditions | Inflammation or blockage of the airways also raises CA 19-9 [3] |
| Other cancers | Gallbladder and bile ducts, stomach, liver, bowel, ovary and lung [1, 3] |
A single high number is never enough to diagnose any illness; the doctor reads it together with your symptoms, liver blood tests and scans.
Is CA 19-9 useful as a check-up or for finding pancreatic cancer early?
No. CA 19-9 is not suitable for screening people without symptoms, because most high results in these people have another cause [2, 3]. In a large study of about 71,000 people without symptoms, fewer than 1 in every 100 people with a high CA 19-9 had pancreatic cancer [3].
Even in people who have symptoms, about 8 in 10 patients with pancreatic cancer have a raised CA 19-9; so a normal number does not rule out cancer [2, 4]. If you have symptoms, the main step is an examination by a doctor and, when needed, a CT scan [8]. Read about the symptoms: What are the symptoms of pancreatic cancer? If several of your close relatives have had pancreatic cancer, read about genetic counselling: Is cancer hereditary?
What is CA 19-9 used for in pancreatic and bile duct cancer?
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Before treatment
The first number helps predict how the disease will behave: among patients who had surgery, those with a normal CA 19-9 before the operation lived, on average, more than twice as long [2]. A very high number may show that the disease is more widespread than the scans suggest; for this reason the doctor sometimes asks for further tests such as a PET scan [2, 6].
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During treatment
The effect of treatment is judged by your general condition, the trend in CA 19-9 and scans, usually every 2 to 3 months [5, 6]. If CA 19-9 rises over several tests in a row, the disease may be growing, but this must be confirmed with other tests [5]. In people who have chemotherapy before surgery, a fall in CA 19-9 is one of the signs that surgery may be possible [6].
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After surgery or chemotherapy
If CA 19-9 returns to normal or falls clearly, patients live longer; if it does not fall, or rises, that is an unfavourable sign [2]. Read more: Pancreatic cancer
- 4
In bile duct cancer
CA 19-9 helps with the diagnosis together with scans, but it is normal in about 3 in 10 patients [7], and jaundice can also raise it for no other reason [2, 3]. Read more: Bile duct and gallbladder cancer
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In stomach and bowel cancer
In stomach cancer it is sometimes used to follow treatment [1]. In bowel cancer, the main follow-up test is CEA [5]: What does a high CEA blood test mean?
When should I call my doctor?
Show your CA 19-9 result to the doctor who ordered it; a single number is neither a reason to worry nor a reason to feel reassured. In these situations do not wait; see a doctor within the next few days:
- yellowing of the skin or the whites of the eyes [8]
- unexplained weight loss with abdominal or back pain, nausea, vomiting, diarrhoea or constipation, especially after the age of 60 [8]
- new diabetes with weight loss, especially after the age of 60 [8]
- if you have pancreatic or bile duct cancer and your CA 19-9 has risen during follow-up, contact your care team [5]
Jaundice with fever and shivering, severe abdominal pain or repeated vomiting needs urgent care: call your local emergency number.
Frequently asked questions
My CA 19-9 is slightly elevated; should I worry?
A slightly raised CA 19-9 with no clear illness is common [3]. The doctor usually checks liver blood tests, blood sugar and HbA1c (average blood sugar over the past three months) and a thyroid test, and if needed asks for scans of the chest, abdomen and pelvis [3]. If the number stays clearly high over 3 months of follow-up, or is 80 or more from the start, further checks for cancer are needed [3].
Does a high CA 19-9 mean I have pancreatic cancer?
My CA 19-9 is normal; does that mean I do not have cancer?
Not necessarily. Of every 10 patients with pancreatic cancer who have symptoms, about 2 have a normal CA 19-9 [2, 4], and most people with an inherited blood group feature called "Lewis negative" make no CA 19-9 [2, 3]. If you have symptoms such as jaundice or unexplained weight loss, keep following them up despite a normal result [8].
I have jaundice and a very high CA 19-9; does that mean cancer?
Not necessarily. A blocked bile duct, even from a stone, raises CA 19-9; usually only a little, but sometimes a great deal if the bile duct is also infected [2, 3]. This is why the doctor usually repeats the test once the bile duct has been opened, for example by placing a small tube (stent) [3, 4]. In people without a bile duct infection, CA 19-9 mostly returned to normal within about three weeks [3]. Either way, always have jaundice checked promptly [8].
I have diabetes and my CA 19-9 is high; what should I do?
High, poorly controlled blood sugar itself raises CA 19-9 [3]. Review the test again with your doctor once your blood sugar is better controlled. But if your diabetes has only just started and you are losing weight for no reason, talk to your doctor about checking the pancreas [8]. Read more: What are the symptoms of pancreatic cancer?
How often is CA 19-9 checked during treatment for pancreatic cancer?
How is CA 19-9 different from CA-125 and AFP?
Each is linked mainly to particular cancers: CA 19-9 to the pancreas and bile ducts, CA-125 to the ovary, and AFP to the liver and germ cell tumours such as testicular cancer [1]. Read: What does a high CA-125 mean? and What does a high AFP mean?
Interpreting CA 19-9: numbers and evidence (for doctors)
For physicians
Diagnostic accuracy in PDAC. In symptomatic patients, sensitivity 79% to 81% and specificity 82% to 90%; PPV in screening 0.5% to 0.9%; false positives in obstructive jaundice 10% to 60%; false negatives in the Lewis-negative phenotype (5% to 10%) [2]. Systematic review (pooled data from 2283 patients): median sensitivity 79% (70 to 90) and median specificity 82% (68 to 91); elevation in non-malignant jaundice lowers specificity, and elevated values should be repeated after relief of jaundice [4]. In the Kim study of 70,940 asymptomatic individuals, sensitivity was 100% and specificity 98.5%, but the PPV was only 0.9% [3]. The Le(a−b−) genotype occurs in about 6% of Caucasian and 22% of non-Caucasian people; nevertheless, in a study of 1482 patients, 27.4% of Lewis-negative patients had a CA 19-9 above 37 U/mL [3].
Prognosis and resectability. A normal preoperative CA 19-9 (below 37 U/mL) is associated with a median survival of 32 to 36 months versus 12 to 15 months with elevated levels; below 100 U/mL suggests likely resectable disease and above 100 U/mL unresectable or metastatic disease; normalisation or a decrease of 20% to 50% or more after resection or chemotherapy is associated with longer survival [2]. In the Berger series (129 resected patients), median survival with CA 19-9 below 37, 38 to 200 and above 200 U/mL was 35, 22 and 16 months, respectively; 80% to 90% of stage III–IV patients have levels above 100 U/mL [3]. IAP biological criterion for borderline resectable disease: CA 19-9 above 500 IU/mL [6].
Recommendations. ESMO (Pan-Asian adaptation 2025): CA 19-9 can be used as a serum marker to measure disease burden and potentially guide treatment decisions [III, B]; after induction therapy, medically fit patients without progression and with a decrease in CA 19-9 should undergo surgical exploration [III, A]; in locally advanced disease, exploration for resection could be discussed with a significant decrease in CA 19-9, clinical improvement and tumour downstaging [IV, B]; PET-CT is useful in localised tumours when distant metastases are uncertain (doubtful imaging or high CA 19-9) [III, B]; in metastatic disease, efficacy should be evaluated every 8 to 12 weeks based on clinical status, CA 19-9 trajectory and imaging [III, A] [6]. ASCO 2006: in locally advanced or metastatic disease on active therapy, CA 19-9 every 1 to 3 months; serial elevations suggest progressive disease, but confirmation with other studies should be sought [5].
Unexplained mild elevation. Suggested work-up: chest X-ray or CT, glucose and HbA1c, liver and thyroid function tests and abdominopelvic CT for gynaecological disease; a benign cause is likely if CA 19-9 changes follow the course of the benign disease; a marked elevation over 3 months of follow-up or a baseline of 80 U/mL or more raises the suspicion of cancer. In cholangitis, normalisation after treatment occurred within two months, and in most patients without cholangitis within three weeks [3].
Cholangiocarcinoma. Meta-analysis of 31 studies (1264 patients and 2039 controls): pooled sensitivity 0.72, specificity 0.84 and area under the curve 0.83; sensitivity was lower in European patients [7]. In primary sclerosing cholangitis, a cut-off of 129 U/mL had a sensitivity of 78.6%, specificity of 98.5%, PPV of 56.6% and NPV of 99.4%; a CA 19-9 above 100 U/mL with a malignant-looking stricture and no bacterial cholangitis suggests perihilar CCA [3].
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References
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Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
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