Gastrointestinal bleeding is a significant cause of morbidity and mortality worldwide. In addition, it constitutes an important part of health expenditures.

In this study, we aimed to determine whether there is a relationship between plasma copeptin levels and the etiology, location and severity of gastrointestinal bleeding.

This study was performed prospectively in 104 consecutive patients who were admitted to an emergency department with complaints of bloody vomiting or bloody or black stool. To evaluate the level of biochemical parameters such as Full Blood Count (FBC), serum biochemistry, bleeding parameters and copeptin, blood samples were obtained at admission. For the copeptin levels, 2 more blood samples were obtained at the 12th and 24th hours after admission.

The values obtained were compared using statistical methods.

In terms of the etiology of bleeding, the copeptin levels in the patients with peptic ulcer were higher than the levels in patients with other gastrointestinal bleeding. However, the difference was not statistically significant.

There were no significant differences among all groups' 0th, 12th and 24th hour levels of copeptin.

We conclude that copeptin cannot be effectively used as a biochemical parameter in an emergency department to determine the etiology and location of gastrointestinal bleeding. It can, however, be used to make decisions on endoscopy and the hospitalization of patients with suspected gastrointestinal bleeding.