CA 125 Test

Home / CA 125 Test

WHAT IS CA 125 TEST? A CA 125 test determines the amount of CA 125 meaning “Cancer Antigen 125” in your blood. Therefore, CA 125 test means Cancer Antigen 125 test. Cancer antigen is a certain protein present in ovarian cancer cells. The protein is produced by the cells and flows into the bloodstream. A… Read More

CA 125 Test


A CA 125 test determines the amount of CA 125 meaning “Cancer Antigen 125” in your blood. Therefore, CA 125 test means Cancer Antigen 125 test.

Cancer antigen is a certain protein present in ovarian cancer cells. The protein is produced by the cells and flows into the bloodstream.

A CA 125 test may be used to monitor certain cancers (such as ovarian, endometrial, or fallopian tube cancers) during and after treatment. 

In some cases, a CA 125 blood test may be used to search for early signs of ovarian cancer in women with a very high risk of the disease. But it is not accurate enough to use for ovarian cancer screening in general. 

This is because many noncancerous conditions can increase the normal CA 125 level. This renders CA 125 blood test imperfect. Different conditions can cause an increase in CA 125, and these include:

  • Normal conditions (such as menstruation and pregnancy).
  • Noncancerous conditions (including uterine fibroids).
  • Certain cancers (such as an ovarian, endometrial, fallopian tube, and peritoneal cancers).

CA 125 marker is the only tumor marker recommended for clinical use when diagnosing and managing ovarian cancer. 

CA 125 normal value is 0.35 units per millimeter (U/mL). Generally, more than 35U/mL of CA 125 could be a sign of ovarian cancer.


  • For Monitoring Cancer Treatments.

Patients with ovarian, endometrial, peritoneal, or fallopian tube cancer may be asked to undergo a CA 125 test regularly to monitor their condition and treatments. For ovarian cancer, additional tests are necessary.

  • For Screening Those At High Risk Of Ovarian Cancer.

Those with a strong family history of ovarian cancer or who have the BRCA-2 gene mutation may be sent for CA 125 test as one way to screen for ovarian cancer. Some doctors may combine it with transvaginal ultrasound every six months, for those at very high risk.

  • For Checking Cancer Recurrence

Rising CA 125 levels may show a return of ovarian cancer after treatment. Regular monitoring of CA 125 has not been shown to improve conditions of ovarian cancer patients, but always leads to additional and worthless rounds of chemotherapy or other treatments.

The early stages of ovarian cancers often witness no symptoms, but the later stages are associated with symptoms that may be non-specific. 

Symptoms may include:

  • Weight loss.
  • Loss of appetite.
  • Bloating.
  • Indigestion.
  • Change of bowel habits.
  • Lump in the abdomen.
  • Fluid in the abdomen.
  • Nausea.
  • Fatigue.
  • Abnormal fullness after eating.
  • Increase in urinating and urge to urinate.
  • Menstrual irregularities.
  • Painful intercourse.
  • Dermatomyositis (a rare inflammatory disease that causes skin and muscle weakness).


  1. Epithelial tumors (90%).
  2. Stromal tumors (7%).
  3. Germ cell tumors.


Ovarian cancer has four stages, and each of them has sub-stages. They are:

Stage 1 (the early stage; with three sub-stages):

  1. Stage 1A.
  2. Stage 1B.
  3. Stage 1C.

Stage 2:

  1. Stage 2A.
  2. Stage 2B.

Stage 3:

  1. Stage 3A.
  2. Stage 3B.
  3. Stage 3C.

Stage 4 (the most advanced stage; with two sub-stages):

  1. Stage 4A.
  2. Stage 4B.


If the purpose is for your blood to be tested only for CA 125 ovarian cancer, you can eat and drink normally before the test. 

The steps are:

  • A qualified nurse will clean and disinfect the area, where the blood is to be drawn, with an antiseptic.
  • He/she will wrap an elastic band around your upper arm for your veins to swell up with blood.
  • A needle is gently inserted into the vein and your blood sample is collected in a small tube attached to the needle.
  • After drawing enough blood, the nurse will remove the needle, while applying pressure on the puncture site, with the cotton wall.
  • He/she covers the puncture site to stop any bleeding.
  • Your blood sample will then be sent to a laboratory for analysis.
  • Your blood sample will be analyzed in the lab and the result is sent to your doctor.

Once your doctor gets your result, your doctor will schedule an appointment to discuss your CA 125 test result with you.


Usually, CA 125 blood test results can vary depending on the laboratory that did the analysis. 

In most cases, CA 125 normal level is less than 35U/mL. With a CA 125 range higher than normal, you may be having a benign condition; or the test result could indicate that you have ovarian, endometrial, peritoneal, or fallopian tube cancer. 

Other tests or procedures may be recommended by your doctor to determine your diagnosis. For those diagnosed with ovarian, endometrial, peritoneal, or fallopian tube cancer, an indication of response to treatment is often proven by a decreasing CA 125 range. An elevated CA 125 level may indicate a recurrence or continued growth of cancer.

Some normal and noncancerous conditions can produce an elevated CA 125 level. They include:

  • Menstruation.
  • Pregnancy.
  • Endometriosis.
  • Liver disease.
  • Uterine fibrosis.
  • Pelvic inflammatory disease.

No major professional organizations recommend using the CA 125 test as a screening test for patients with an average risk of ovarian cancer.


The risks of a CA 125 blood test are common to all blood tests. These common risks include:

  • The obstacle in obtaining a blood sample (finding a vein).
  • Bleeding at the puncture site.
  • Fainting due to loss of blood (which is usually rare).
  • Infection at the puncture site.


More than 80% of ovarian cancers are discovered after they had spread. This is why researchers are in search of a way to effectively screen for ovarian cancer. 

Many of these researchers are looking at a particular biomarker, CA 125 tumor marker. Unfortunately, this marker test is imperfect. 

Elevated levels of CA 125 can be caused by several other factors such as uterine fibrosis, pregnancy, menstruation, etc. These “false positive” and “false negative” results can lead to unnecessary clinical tests and procedures.

About 20% of women with ovarian cancer do not have elevated CA 125 levels. The tests lack specificity in pre-menopausal women. Due to its inaccuracy, widespread screening for ovarian cancer lacks recommendation. It is important to note that while other tests can guide your doctor, the only sure diagnosis to confirm whether you have ovarian cancer is a biopsy.


  • What cancers do CA 125 tests detect?

Cancer antigen (125) is a protein in most ovarian cancer cells and is secreted into the bloodstream, and can be measured. CA 125 can also be seen in other normal, noncancerous, and cancerous cells in the body. Eg: uterine fibroid, fallopian tube cancer, pancreatic cancer, breast cancer, lung or colorectal cancers.

  • Is CA 125 only for ovarian cancer?

CA 125 is the only tumor marker recommend for clinical use in the diagnosis and management of ovarian cancer.

  • How do you check for ovarian cancer?

The two tests used most often (in addition to a complete pelvic exam) to screen for ovarian cancer include transvaginal ultrasound (TVUS) and the CA 125 blood test. TVUS is a test that uses sound waves to look at the uterus, fallopian tube, and ovary, by putting an ultrasound wand into the vagina.

  • Where is ovarian cancer pain located?

One of the most common ovarian cancer symptoms is pain. It is often felt in the stomach, side, or back.

  • What are the symptoms of Stage 1 ovarian cancer?

The early symptoms of ovarian cancer are:

  • Abdominal bloating, pressure, and pain.
  • Abnormal abdominal fullness after eating only a little.
  • Eating difficulties.
  • Increase in urination.
  • Increased urge to urinate.