Ovarian cancer does not reliably show up in standard blood work like a complete blood count or metabolic panel. There are specialized blood tests that detect proteins linked to ovarian cancer, but none are accurate enough to serve as a screening tool for women without symptoms. The most commonly used marker, CA-125, misses about half of early-stage ovarian cancers and can be elevated by dozens of non-cancerous conditions.
That said, blood tests play an important role once ovarian cancer is suspected. Understanding what these tests can and cannot tell you helps make sense of results you may already have in hand.
What Routine Blood Work Can and Cannot Show
A standard complete blood count (CBC) and comprehensive metabolic panel (CMP), the tests most people get at an annual physical, are not designed to detect ovarian cancer. They measure blood cell counts, electrolytes, liver enzymes, and kidney function. These values can sometimes look abnormal in someone with advanced cancer (low red blood cells from chronic disease, elevated platelet counts, or shifts in liver markers if cancer has spread), but those changes are vague. They point to dozens of possible causes and would never lead a doctor to suspect ovarian cancer on their own.
There is currently no approved screening blood test for ovarian cancer. The American College of Obstetricians and Gynecologists states this plainly: some tests are marketed directly to consumers as ovarian cancer screens, but they are not accurate or reliable for women who have no symptoms. This is a critical distinction, because many people assume a normal blood panel means nothing serious is going on, when in reality, early ovarian cancer simply doesn’t disturb these routine markers in a noticeable way.
CA-125: The Most Common Tumor Marker
CA-125 is a protein found on the surface of ovarian cancer cells. When levels in the blood rise above 35 units per milliliter, it raises suspicion for malignancy. About 80% of ovarian cancers overall produce elevated CA-125. That number sounds reassuring until you break it down by stage: in early-stage disease (stages I and II), only about 50% of cases show a high reading. In advanced disease, that figure jumps to 92%.
The test is also plagued by false positives. CA-125 rises during menstruation, pregnancy, and ovulation. It climbs with endometriosis, pelvic inflammatory disease, uterine fibroids, liver disease, and even fluid buildup in the chest or abdomen from unrelated causes. In premenopausal women especially, an elevated result is more likely to reflect one of these benign conditions than cancer. This is the core reason CA-125 is not recommended as a screening tool: too many healthy people get alarming results, and too many early cancers slip through undetected.
Where CA-125 does prove useful is in monitoring. If you’ve already been diagnosed with ovarian cancer, doctors track CA-125 levels over time to gauge how treatment is working or to catch a recurrence early.
HE4: A Newer, More Specific Marker
HE4 (human epididymis protein 4) is a blood marker that fills some of the gaps CA-125 leaves behind. Its biggest advantage is specificity: in studies comparing the two, HE4 was far less likely to be elevated in women with benign ovarian masses, meaning fewer false alarms. One study found HE4 had 100% specificity for distinguishing cancerous masses from benign ones, compared to about 90% for CA-125.
HE4 also performs better at catching early-stage disease. Its sensitivity for early-stage ovarian cancer reached roughly 93% in one study, compared to 63% for CA-125 at the same stage. It was particularly strong at detecting early serous tumors, the most common and aggressive subtype. That said, HE4 is less effective at flagging mucinous cancers and non-epithelial types, so it has blind spots of its own.
The two markers work best together. When CA-125 and HE4 are combined, sensitivity for detecting ovarian cancer rises to about 93%, capturing cases that either test alone would miss.
The ROMA Score: Combining Markers With Risk
Rather than looking at CA-125 or HE4 in isolation, doctors sometimes use a calculation called ROMA (Risk of Ovarian Malignancy Algorithm). This formula takes your CA-125 level, your HE4 level, and your menopausal status, then generates a percentage score estimating the likelihood that an ovarian mass is cancerous.
The math behind ROMA weights HE4 more heavily in premenopausal women and gives more influence to CA-125 in postmenopausal women, reflecting how each marker behaves across age groups. The output is a single number that helps your doctor decide how urgently to investigate a mass found on imaging. A high ROMA score typically triggers referral to a gynecologic oncologist rather than a general surgeon, which improves outcomes because specialists are more likely to perform the optimal procedure.
What Happens After an Abnormal Result
An elevated blood marker alone does not confirm ovarian cancer. It triggers a chain of further testing. The typical next step is an ultrasound, often a transvaginal scan where a small probe is inserted into the vagina to get detailed images of the ovaries. Sometimes an abdominal ultrasound is done as well. Together, these scans reveal the size, shape, and internal structure of any masses, helping distinguish fluid-filled cysts (usually benign) from solid or complex growths.
If both the blood test and ultrasound raise concern, you’ll likely move on to a CT scan to check whether anything has spread beyond the ovaries. From there, confirmation requires tissue. That can mean a needle biopsy guided by imaging, a laparoscopy (a minimally invasive procedure using a camera inserted through a small abdominal incision), or in some cases, surgery to remove the mass entirely for examination. Only a pathologist looking at actual tissue under a microscope can definitively diagnose ovarian cancer.
Why Screening Remains So Difficult
Ovarian cancer is relatively rare, affecting about 1 in 78 women over a lifetime. When a disease is uncommon, even a test with good accuracy produces more false positives than true positives when applied to the general population. Large trials that attempted to screen healthy women with CA-125 and ultrasound did not reduce deaths from ovarian cancer and led to unnecessary surgeries that carried their own risks.
This is why current guidelines reserve these blood tests for women who already have symptoms (persistent bloating, pelvic pain, difficulty eating, or urinary urgency that’s new and frequent) or who have a known pelvic mass. For women at very high genetic risk, such as those carrying BRCA1 or BRCA2 mutations, doctors may offer more frequent monitoring, but even in this group, no blood test strategy has been proven to catch the disease early enough to change survival rates consistently.
Liquid Biopsies and What’s on the Horizon
Researchers are working on blood tests that go beyond single proteins. Liquid biopsies analyze fragments of tumor DNA, tiny RNA molecules, and other cellular debris that cancers shed into the bloodstream. Early studies show these approaches can detect ovarian cancer signals that CA-125 and HE4 miss, especially when combined with artificial intelligence models that weigh multiple data types at once.
These technologies are not yet available for routine clinical use. The main obstacles are standardizing the tests across laboratories and proving through large, long-term studies that they actually catch cancers early enough to save lives. For now, CA-125 and HE4, used alongside imaging, remain the practical tools available to you and your doctor.