Glycoantigen 199 will not be elevated when a woman has her blood drawn during her period, and the results of this test have little to do with the onset of menstruation. CA199 is a glycoprotein and a tumor marker, and several systemic diseases may cause CA199 to increase, but menstruation will not cause CA199 to increase. CA199 is mainly used to detect pancreatic cancer, but it needs to be combined with alpha-fetoprotein and carcinoembryonic antigen, etc. CA199 is also useful for the diagnosis of gastrointestinal tumors, and when there is hepatocellular carcinoma, CA199 will also be elevated. There are some non-tumor diseases, which may also cause CA199 increase, such as acute pancreatitis, acute hepatitis, cirrhosis, cholestatic cholangitis, cholelithiasis and so on. If CA199 is significantly elevated in blood tests, you need to go to the hospital for further examination, such as ultrasound, CT or MRI, etc., in order to make a clear diagnosis.