CA 125: the tumour marker in ovarian cancer and what a raised value means
According to the NVKC, the Dutch society for clinical chemistry and laboratory medicine, CA 125 (cancer antigen 125) is a substance made by normal cells and also by tumour cells. According to the NVKC, cells in an ovarian tumour make extra CA 125, which is why CA 125 serves as a tumour marker for ovarian cancer.
According to the NVKC, besides ovarian cancer a raised CA 125 can also occur in pregnancy, in benign tumours and, in people without a tumour, in liver cirrhosis and in inflammation of the peritoneum, the pleura or the pericardium. According to the NVKC, a normal value cannot rule out ovarian cancer. Only a blood test shows how much CA 125 is in the blood.
The NVKC gives a reference value for CA 125 of 35 kU/L or less. Star-SHL uses 0 to 35 kE/l, Unilabs 0 to 30.2 kU/l and Diagnostiek voor U below 30 U/mL.
Turnaround 24 hours, estimate Turnaround: up to 24 hours after your blood draw (estimate).
According to the NVKC, CA 125 is a tumour marker made by normal cells and tumour cells, used to follow the effect of treatment for ovarian cancer. According to the NVKC, a normal CA 125 cannot rule out ovarian cancer.
- The NVKC gives a reference value for CA 125 of 35 kU/L or less; Star-SHL uses 0 to 35 kE/l, Unilabs 0 to 30.2 kU/l and Diagnostiek voor U below 30 U/mL.
- According to the NVKC, CA 125 can also be raised in pregnancy and benign tumours, and in people without a tumour in liver cirrhosis and inflammation of the peritoneum, pleura or pericardium.
- According to MedlinePlus, CA 125 is in general not used to screen healthy women without a diagnosis for ovarian cancer.
Reference Ranges
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Reference values can vary between laboratories. Discuss your results with your GP for explanation and treatment decisions.
CA-125: what Dutch laboratories use
| Laboratory | Group | Reference value (kU/l) | Relative scale |
|---|---|---|---|
| Star-shl | · Everyone | 0–35 kE/l kE/l | |
| Unilabs | · Everyone | 0.0–30.2 kU/l |
0 30.2
|
| Diagnostiek voor U | · Everyone · a limit, not a range | < 30 U/mL U/mL |
Source: Star-shl
Source: Unilabs
Source: Diagnostiek voor U
Each value as the laboratory itself publishes it, retrieved in 2026.
CA-125: what this test measures
According to the NVKC, the CA 125 test determines the amount of CA 125 in the blood, expressed in kU/l or U/mL. Star-SHL measures with an electrochemiluminescence immunoassay and Unilabs with a one-step immunometric immunoassay, and according to the NVKC the measurement methods differ between laboratories.
CA-125: why this value matters
According to the NVKC, CA 125 serves to follow the effect of treatment for ovarian cancer. According to the NVKC, before treatment starts CA 125 is measured as a baseline, and if the value then falls, the treatment is effective according to the NVKC. According to the NVKC, CA 125 can also be used to check whether a previously treated tumour in the ovaries is coming back.
CA-125: how the blood test works
- Referral
- No GP referral needed. After the order we arrange the referral through ZorgDomein, within one business day; orders after 17:00 or at the weekend start on the next business day. ZorgDomein emails a barcode, and that barcode is what the draw site needs.
- The draw
- A blood draw from a vein in the arm, at a partner laboratory's draw site. No home kit, no finger prick.
- Results
- Turnaround: up to 24 hours after your blood draw (estimate).
- Where
- 650+ draw sites run by independent laboratories across the Netherlands. Draw sites
CA-125: when is testing worthwhile?
According to the NVKC, the doctor has CA 125 measured in patients with ovarian cancer or an increased chance of it. According to MedlinePlus, the test may also be done in a woman with symptoms or ultrasound findings that suggest ovarian cancer. According to MedlinePlus, in general the test is not used to screen healthy women without a diagnosis for ovarian cancer.
CA-125: symptoms of a high or low value
Low Levels
According to the NVKC, a CA 125 within the reference value cannot rule out ovarian cancer. According to the NVKC, if CA 125 falls during treatment for ovarian cancer, this generally means the cancer is responding to the treatment. According to the NVKC, a fast fall of CA 125 after treatment for ovarian cancer is no guarantee, however, because the disease can still come back.
High Levels
According to the NVKC, a rising CA 125 during or after treatment for ovarian cancer generally means the cancer is not responding or has come back. According to MedlinePlus, in a woman without a diagnosis of ovarian cancer a high CA 125 may point to ovarian cancer, to other types of cancer or to diseases that are not cancer, such as endometriosis. According to MedlinePlus, most healthy women with an elevated CA 125 do not have ovarian cancer or any other cancer.
CA-125: causes of a low or high value
What lowers the value
-
Effective treatment of ovarian cancer
If CA 125 falls during treatment for ovarian cancer, this generally means the cancer is responding to the treatment.
What raises the value
-
Ovarian cancer
Cells in an ovarian tumour produce extra CA 125, which is why CA 125 is used as a marker for ovarian cancer.
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Endometriosis
In a woman without a diagnosis of ovarian cancer, a high CA 125 can also indicate diseases that are not cancer, such as endometriosis.
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Ovarian cyst
Other diseases can also put more CA 125 in the blood, for example a fluid-filled sac on the ovary.
-
Liver cirrhosis
In people without a tumour, CA 125 can be raised in liver cirrhosis.
-
Inflammation of the peritoneum, pleura or pericardium
In people without a tumour, CA 125 can be raised in inflammation of various membranes such as the peritoneum, pleura or pericardium.
CA-125: lifestyle and this value
Discuss a raised CA 125 with your GP. According to MedlinePlus, any woman with an abnormal CA 125 test needs further tests, and sometimes surgery is needed to confirm the cause.
CA-125: frequently asked questions
Is CA 125 a screening test for ovarian cancer?
No, according to MedlinePlus CA 125 is in general not used to screen healthy women for ovarian cancer when there is no diagnosis yet. According to the NVKC, a normal CA 125 cannot rule out ovarian cancer either.
Why is CA 125 preferably measured in the same laboratory each time?
According to the NVKC, when following therapy it matters that CA 125 is always measured by the same laboratory, because the measurement methods differ between laboratories.
CA-125: sources
- Star-shl, Labbepalingen (referentiewaarden per bepaling), star-shl.nl, geraadpleegd 2026-10-01 (retrieved 2026) star-shl.nl
- Unilabs, Bepalingenklapper (referentiewaarden per bepaling), bepalingenklapper.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenklapper.nl
- Diagnostiek voor U, eLabgids (Referentiewaarden DvU), diagnostiek.getincontrol.eu, geraadpleegd 2026-10-01 (retrieved 2026) diagnostiek.getincontrol.eu
- NVKC, Alles over testen: CA 125, allesovertesten.nl, geraadpleegd 2026-10-16 (retrieved 2026) allesovertesten.nl
- MedlinePlus Medical Encyclopedia, CA-125 blood test, medlineplus.gov, review date 2024-10-14, geraadpleegd 2026-10-16 (retrieved 2026) medlineplus.gov
- NHG, Thuisarts: Ik krijg onderzoeken in het ziekenhuis om te weten of ik eierstok-kanker heb, thuisarts.nl, geraadpleegd 2026-10-16 (retrieved 2026) thuisarts.nl
Results without a doctor's assessment
You receive your values with the unit and reference range. A doctor's assessment is not part of this site. Discuss your results with your GP for explanation and treatment decisions.