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Cancer Antigen 19-9 (CA 19-9) with Serum/Plasma

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

This test measures a protein (antigen) that may be produced in higher amounts by certain cancers, including pancreatic cancer, and sometimes by other types of cancer or non-cancerous conditions.

Quick summary

["CA 19-9 helps monitor cancer progression and response to treatment."]

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

Key facts at a glance

LOINC
50780-6
Short code
CA19-9 PF
Synonyms
Cancer Ag19-9 Pcar-aCnc
Category
chemistry
Sample
serum
Container
Sterile, leak-proof container without anticoagulants; red-top vacuum tube acceptable for transport
Units
N/A
Ref low
0
Ref high
37
Critical range
0.5 N/A – —
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
Immunoassay (Chemiluminescent)
CPT
86316
SNOMED
165539006
Specimen volume
2-5 mL of pericardial fluid
Stability
Room temperature: 8 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 3 months
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
24–72 hours
Order
routine

What Is CA 19-9 Used For?

CA 19-9 is primarily used to detect or track pancreatic cancer, though it can also be elevated in other cancers like bile duct, stomach, or colorectal cancers. It may also appear in non-cancerous conditions such as chronic pancreatitis or liver disease. This test is often used alongside other diagnostic tools to guide treatment decisions.

How Is the Test Performed?

A blood sample is drawn from a vein, usually in your arm. The blood is then sent to a lab where it is tested for the presence of CA 19-9. The test can be performed on either serum or plasma, depending on the lab’s protocol.

Why Might Your Doctor Order This Test?

Your doctor may order a CA 19-9 test if you have symptoms of pancreatic cancer (such as abdominal pain, unexplained weight loss, or jaundice), if you have a history of pancreatic cancer or other related cancers, or if you are undergoing treatment for these conditions. It can also be used to monitor cancer spread or treatment effectiveness.

What Do Results Mean?

Elevated levels of CA 19-9 can indicate cancer, but they can also be raised in non-cancerous conditions. A single elevated result does not definitively diagnose cancer. Your doctor will consider your symptoms, medical history, and other test results to interpret the results accurately.

Reference range

No established reference range for pericardial fluid; serum reference range <37 U/mL is commonly applied as interpretive baselineN/A

Specimen: serum

No special patient preparation required for pericardial fluid sampling; pericardiocentesis performed by qualified clinician

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

CA 19-9 is a tumor marker that can be useful in diagnosing pancreatic cancer and assessing its progression. However, it is not specific to cancer alone, so it should be used alongside other diagnostic tests and clinical findings. High levels may suggest cancer, but further testing is required to confirm a diagnosis. Regular monitoring of CA 19-9 levels can help track cancer activity during treatment.

Short name

CA 19-9 Test

Frequently asked questions

What Are the Possible Causes of Elevated CA 19-9 Levels?
Elevated CA 19-9 can be caused by pancreatic cancer, but it can also be linked to other conditions such as chronic pancreatitis, liver disease, bile duct blockages, or certain infections. If your levels are high, your doctor will investigate further to determine the underlying cause.
How Often Should I Get This Test?
The frequency of CA 19-9 testing depends on your medical condition. If you have pancreatic cancer or are at high risk, your doctor may recommend regular monitoring. If you have no known risk factors, this test may not be routinely recommended unless symptoms appear or further evaluation is needed.
Can CA 19-9 Levels Decrease After Treatment?
Yes, CA 19-9 levels can decrease after cancer treatment if the tumor is effectively controlled. However, the test is not always reliable for this purpose due to its non-specific nature. Your doctor will use the results in combination with other assessments to evaluate treatment success.
  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