The CA 19-9 test measures the level of the CA 19-9 protein (a tumor marker) in the blood. It is mainly used to:

• Help monitor pancreatic cancer treatment and recurrence.
• Assist in evaluating other gastrointestinal cancers, such as bile duct, gallbladder, or colorectal cancers.
• Sometimes used to check for disease progression in certain cancers, but not recommended for routine screening in healthy individuals.