CA 15-3 — What It Means in Your Blood Test
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Tumour marker results are complex. This page explains what the test measures — your doctor or specialist interprets your result in full clinical context, alongside your history and other tests.
What CA 15-3 cannot tell you
CA 15-3 is not a screening test for breast cancer. Benign breast and liver conditions raise it, and a normal result does not rule cancer out. Your doctor reads it with an examination and imaging [ASCO, 2007].
This is a protein fragment some cells shed, which several benign conditions can raise.
A raised CA 15-3 often has a benign cause such as a liver or breast condition. It is used mainly to follow a known breast cancer, not to find one.
Also known as: Cancer antigen 15-3, Carbohydrate antigen 15-3
This isn't a case where higher or lower is better. Your body keeps it in a narrow band, and both directions can matter.
Last reviewed: 2026-08-16
What does CA 15-3 do in your body?
A specialist uses CA 15-3 mostly to watch a breast cancer that has already spread, seeing whether it settles with treatment. It is not used to screen and its trend matters most [ASCO, 2007].
What is CA 15-3?
CA 15-3 is a fragment of a protein carried on the surface of many cells, including breast cells. Several conditions of the breast and liver can shed more of it into the blood.
Why is CA 15-3 tested?
You may have this test to keep track of a breast cancer already found, within a specialist's assessment. It is read with an examination and a scan.
What can raise CA 15-3
Common, non-cancer causes
- Benign breast conditions, such as fibroadenoma or mastitis [NACB, 2010]
- Long-standing liver disease, such as hepatitis or cirrhosis [NACB, 2010]
- Some benign ovarian and endometrial conditions [NACB, 2010]
- Pregnancy and breastfeeding [NACB, 2010]
Causes a doctor will also consider
- Breast cancer, which a specialist follows with CA 15-3 once it is known about, mainly when advanced [ASCO, 2007]
- Some other cancers, considered only in full clinical context [NACB, 2010]
One CA 15-3 reading means little alone. A specialist watches how it changes across tests, and reads it with an examination and imaging [ASCO, 2007].
What is a normal CA 15-3 range?
- India
- No India-specific national reference interval is published for this parameter; your lab's printed range is the most reliable comparison.
- Global
- Laboratories often report against a general figure of about 30 U/mL, but benign liver and breast conditions can raise it; what a value means depends on the wider picture [NACB, 2010]
Ranges vary by lab, method and equipment — the range printed on your own report is the one that applies to your result.
Source: [ASCO, 2007]
What does your CA 15-3 value mean?
There is no widely-accepted set of value bands for this parameter. Compare your result with the reference range printed on your own report, and discuss it with your doctor.
What does a high CA 15-3 result mean?
A raised CA 15-3 often reflects a benign breast or liver condition. Your doctor weighs these first, with an examination and imaging, before any next step.
What does a low CA 15-3 result mean?
A low or within-range CA 15-3 is reassuring when following a known condition. It is still read with your examination and scan, as no single marker is enough.
What can affect your CA 15-3 result?
- Benign breast conditions
- Long-standing liver disease
- Pregnancy and breastfeeding
- The laboratory method — the same lab is used for monitoring
Questions to ask your doctor
About this result
- My CA 15-3 is [value] U/mL — read with my examination and scan, how concerned should we be?
- Could a benign breast or liver condition explain my CA 15-3?
What to do next
- Should the CA 15-3 be repeated at the same lab to show the trend?
- Do my result and imaging together point to any next step?
Frequently asked questions
- What is CA 15-3?
- CA 15-3 is a fragment of a protein carried on the surface of many cells, including breast cells. Several conditions of the breast and liver can shed more of it into the blood. You may have this test to keep track of a breast cancer already found, within a specialist's assessment. It is read with an examination and a scan.
- What is a normal CA 15-3 test (breast marker) range?
- A typical adult range is around Laboratories often report against a general figure of about 30 U/mL, but benign liver and breast conditions can raise it; what a value means depends on the wider picture [NACB, 2010]. No India-specific national reference interval is published for this parameter; your lab's printed range is the most reliable comparison. Ranges vary by lab, method and equipment — the range printed on your own report is the one that applies to your result.
- What does a high CA 15-3 result mean?
- A raised CA 15-3 often reflects a benign breast or liver condition. Your doctor weighs these first, with an examination and imaging, before any next step.
- What does a low CA 15-3 result mean?
- A low or within-range CA 15-3 is reassuring when following a known condition. It is still read with your examination and scan, as no single marker is enough.
- What can affect your CA 15-3 result?
- Several everyday factors can influence it, including Benign breast conditions, Long-standing liver disease, Pregnancy and breastfeeding, The laboratory method — the same lab is used for monitoring.
Sources
- ASCO (2007) — ASCO 2007 Update of Recommendations for the Use of Tumor Markers in Breast Cancer
- NACB (2010) — NACB Laboratory Medicine Practice Guidelines: Use of Tumor Markers in Testicular, Prostate, Colorectal, Breast, and Ovarian Cancers
Part of the Tumour Markers
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