CA 19-9
CA 19-9 is a protein shed by tumor cells into the bloodstream. This test measures CA 19-9 levels and is primarily used to monitor treatment of pancreatic cancer.
Category: Tumor Markers
Also known as: ca 19-9, ca19-9, ca 19 9, cancer antigen 19-9
Reference range: 0–37 U/mL (Source: ABIM)
Standard unit: U/mL
High values may indicate
High CA 19-9 levels may indicate pancreatic cancer, bile duct cancer, gallbladder cancer, or non-cancerous conditions such as pancreatitis, bile duct obstruction, or liver disease.
Low values may indicate
Low CA 19-9 levels are normal and may indicate a good response to cancer treatment in patients being monitored.
Frequently asked questions
- What is a normal CA 19-9 level?
- A typical reference range for CA 19-9 is 0–37 U/mL (source: ABIM). Reference ranges vary by laboratory, age, and sex, so always compare against the range on your own lab report.
- What units is CA 19-9 measured in?
- CA 19-9 is most commonly reported in U/mL. Labs in different countries may use other units — you can convert between them with BloodId's blood test unit converter.
- Where do CA 19-9 reference ranges come from?
- BloodId uses ABIM standard reference ranges and educational information from MedlinePlus (see our methodology). Reference ranges still vary by lab, age, and sex, so always compare against your own report.
- Can I track CA 19-9 over time?
- Yes. Upload results from any lab and BloodId charts your CA 19-9 over time against its reference range, so you can see whether the trend is rising, falling, or stable.