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Tumor Markers

CA 125 in women: ovarian cancer, symptoms and why a normal value does not say everything

According to the NVKC, cells in an ovarian tumour make extra CA 125, a substance normal cells make too, which is why CA 125 is used as a marker for ovarian cancer. According to Thuisarts, ovarian cancer gives no symptoms as long as it is only in the ovaries, and is therefore often discovered late.

According to Thuisarts, more CA 125 than normal can point to ovarian cancer, but also to a cyst on the ovary or an inflammation in the abdomen, and according to Thuisarts a normal CA 125 does not rule out ovarian cancer. Only a blood test shows how much CA 125 is in the blood.

Diagnostiek voor U uses a reference value below 30 U/mL for CA 125.

Doctor's Assessment Included

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

Female
kU/l
Normal < 35 High

Reference ranges may vary between laboratories. When you order a test, a BIG-registered doctor assesses your personal results in context. For treatment decisions, discuss your results with your GP.

Check your own value

CA-125: what Dutch laboratories use

Reference ranges by group, in kU/l
Star-shl · Everyone 0–35 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
0 33.22 kU/l

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

A Diagnostiek voor U CA 125 result counts in U/mL how much cancer antigen 125 is in the blood, measured on an Atellica analyser from a heparin tube. According to the NVKC, measurement methods differ between laboratories.

CA-125: why this value matters

In women with ovarian cancer, the doctor can use CA 125 to check whether a treatment is working and whether a treated tumour is coming back, according to the NVKC. Ovarian cancer itself usually only gives symptoms when the cancer is large or has spread, according to Thuisarts. According to Thuisarts, ovarian cancer can give symptoms such as pain low in the abdomen, a full feeling, a bloated abdomen, weight loss without trying and passing urine more often than normal, although these symptoms can also have other causes.

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.
Where
650+ draw sites run by independent laboratories across the Netherlands. Draw sites

CA-125: when is testing worthwhile?

According to MedlinePlus, a CA 125 test may be done in a woman with symptoms or ultrasound findings that suggest ovarian cancer. According to Thuisarts, in a woman being investigated in hospital for ovarian cancer, more testing is usually needed after a CA 125 result, because the result neither proves nor rules out ovarian cancer.

CA-125: symptoms of a high or low value

Low Levels

According to Thuisarts, a normal CA 125 does not mean ovarian cancer is ruled out: a woman can have ovarian cancer even without more CA 125 than normal. During treatment for ovarian cancer, a falling CA 125 value is according to the NVKC generally a sign that the cancer is responding.

High Levels

In a woman without a diagnosis of ovarian cancer, a high CA 125 can according to MedlinePlus point to ovarian cancer, to other types of cancer or to diseases that are not cancer, such as endometriosis. According to the NVKC, pregnancy and benign tumours can raise CA 125 as well.

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.

  • 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.

  • 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

According to Thuisarts, ovarian cancer is hereditary in about 12 of 100 women with the disease, and you discuss an abnormal CA 125 result with your GP.

CA-125: frequently asked questions

Does a raised CA 125 mean I have ovarian cancer?

According to Thuisarts, a raised CA 125 can point to ovarian cancer, but it does not have to: a cyst on the ovary or an inflammation in the abdomen can also give more CA 125 in the blood.

CA-125: sources

  1. Star-shl, Labbepalingen (referentiewaarden per bepaling), star-shl.nl, geraadpleegd 2026-10-01 (retrieved 2026) star-shl.nl
  2. Unilabs, Bepalingenklapper (referentiewaarden per bepaling), bepalingenklapper.nl, geraadpleegd 2026-10-01 (retrieved 2026) bepalingenklapper.nl
  3. Diagnostiek voor U, eLabgids (Referentiewaarden DvU), diagnostiek.getincontrol.eu, geraadpleegd 2026-10-01 (retrieved 2026) diagnostiek.getincontrol.eu
  4. NVKC, Alles over testen: CA 125, allesovertesten.nl, geraadpleegd 2026-10-16 (retrieved 2026) allesovertesten.nl
  5. MedlinePlus Medical Encyclopedia, CA-125 blood test, medlineplus.gov, review date 2024-10-14, geraadpleegd 2026-10-16 (retrieved 2026) medlineplus.gov
  6. 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

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