Skip to content

Serum/plasma cancer antigen 19-9 (CA 19-9) concentration

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of a protein called cancer antigen 19-9 in your blood. It may help detect or monitor certain cancers, including pancreatic cancer.

Quick summary

["CA 19-9 can help track cancer progression or response to treatment."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
24108-3
Short code
CA19-9
Synonyms
Cancer Ag19-9 SerPl-aCnc
Category
chemistry
Sample
serum
Container
SST (Serum Separator Tube) or Red-top tube; also acceptable in lithium-heparin plasma tube
Units
N/A
Ref low
0
Ref high
37
Critical range
0.5 N/A – 1000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Immunoassay (Electrochemiluminescence or Chemiluminescent)
CPT
86301
SNOMED
1152690006
Specimen volume
1 mL serum or plasma
Stability
Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 3 months; Avoid repeated freeze-thaw cycles
Hemolysis max
100
Lipemia max
500
Icterus max
30
TAT
4–24 hours
Order
routine

What Is CA 19-9 Used For?

CA 19-9 is primarily used as a biomarker for pancreatic cancer screening and monitoring. It may also be checked in other cancers, such as stomach, bile duct, or gallbladder cancers, though less commonly. Doctors may order this test if you have symptoms like abdominal pain, unexplained weight loss, or a known risk for these cancers.

How Is the Test Performed?

A blood sample is taken from a vein in your arm. The blood is sent to a lab where it is analyzed for the presence of CA 19-9 protein using immunoassay techniques. This process helps determine the concentration of the protein in your blood.

What Does a High or Low Level Mean?

High levels of CA 19-9 can indicate pancreatic cancer or other cancers mentioned above. However, elevated levels can also occur in non-cancerous conditions, such as chronic pancreatitis or liver disease. Low levels typically suggest no cancer is present, but they don’t rule out other conditions.

When Might You Need This Test?

Your doctor may recommend a CA 19-9 test if you have symptoms related to cancer, a known history of cancer, or if you are undergoing treatment for a cancer that may produce CA 19-9. It may also be used as part of follow-up care to monitor the progression or effectiveness of treatment.

Reference range

Normal: <37 U/mL; Values >37 U/mL may indicate malignancy or benign conditionsN/A

Specimen: serum

No fasting required. Specimen should be collected prior to administration of biotin-containing supplements or medications when possible, as high biotin levels may interfere with immunoassay results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: CA 19-9 is a tumor marker that can assist in diagnosing, staging, and monitoring pancreatic cancer. While it is not a definitive test on its own, it can provide important information alongside other diagnostic tests, such as imaging studies. It is important to discuss results with your healthcare provider, as they will consider the full clinical picture when interpreting your test results.

Short name

CA 19-9 blood test

Frequently asked questions

Why might my CA 19-9 test be ordered?
Your doctor might order this test if you have symptoms like unexplained weight loss, abdominal pain, or jaundice, or if you have a known risk for pancreatic or other related cancers. It may also be used during cancer treatment to check how well your body is responding to therapy.
Can CA 19-9 levels be affected by other health conditions?
Yes, conditions such as chronic pancreatitis, liver disease, or certain infections can cause CA 19-9 levels to be elevated. It’s important to inform your doctor about any medical conditions you have, as they will help determine if the test results are relevant to your situation.
What should I do if my CA 19-9 test results are abnormal?
If your test results are abnormal, your doctor will discuss them with you and may recommend further testing or follow-up. They will consider your overall health and symptoms to determine the next steps, which could include additional imaging, biopsies, or other diagnostic procedures.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy