Cancer Antigen 15-3 (CA 15-3)

A tumor marker used to monitor breast cancer.

Last reviewedJune 16, 2026

Serum

sample type

~5 mL

blood needed

~7 days

results in app

Any time of day

best timing

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On this page

Why test Reference ranges What you'll learn What affects it How testing works Sources FAQ

In short

Cancer antigen 15-3, or CA 15-3, is a protein shed into the blood by certain cells, including breast tissue. Small amounts are present in healthy people.

It is measured as a tumor marker, most often in the context of breast conditions, but it is not specific to cancer.

Cancer Markers (Screening)

Reviewed against DGKL reference practice.

Why test this?

CA 15-3 is used mainly to monitor people already diagnosed with breast cancer, to watch response to treatment and check for return. It is not a screening test for healthy people and is often normal in early breast cancer.

Mild rises are common and often benign, seen with liver disease, some non-cancer breast and ovarian conditions, and other illnesses. A high or rising level needs a doctor to interpret in the full picture.

What is a normal result?

Aniva reads your result against research-backed ranges, not just the lab's wide normal. The reference shown below is specific to this biomarker.

Ranges are guidance only. CA 15-3 is an upper-cutoff marker.

Group	Common upper guide (SI)
Adults	up to about 30 kU/L (U/mL)

The exact cutoff depends on the assay. Aligned to German laboratory practice (DGKL).

Ranges are guidance and vary by lab and assay, aligned with DGKL practice. Always read your result against your own lab's reference interval.

What insights will this test give you?

A baseline CA 15-3 level, most useful when tracked over time.
An early flag that, with your doctor, may prompt further questions.
Context your concierge can read alongside your history in a personalized action plan.

What can affect this result?

What can skew the result

Liver disease and some benign breast, ovarian, and other conditions can raise CA 15-3. It is often normal in early cancer, so a normal result does not rule cancer out. Results from different assays are not interchangeable.

Best interpreted with

Sometimes read alongside CEA when monitoring breast cancer, and always with imaging and clinical history.

How is this tested?

Sample

Serum

Blood needed

~5 mL

Method

Immunoassay

Best timing

Any time of day

Sources. The evidence behind this

Mayo Clinic Laboratories: CA 15-3, Serum

Medscape: CA 15-3 Reference Range

MedlinePlus: CA 15-3 Blood Test

Common questions

Which Aniva panels include this marker?

Cancer and Tumor Screening

These tests measure key tumor markers linked to the most common and serious cancers.