Abstract. The present study aimed to identify novel predictors of upper gastrointestinal (GI) bleeding by assessing change ratios of blood test variables. Records of 1,023 patients (431 men and 592 women) who underwent endoscopy between October 2014 and September 2015 at the National Hospital Organization Shimoshizu Hospital (Yotsukaido, Japan) were retrospectively analyzed. Patients whose blood test variables for the time-point of endoscopy and three months previously were available were enrolled and subsequently categorized into a group with and another one without upper GI bleeding (n=32 and 84, respectively), and the respective change ratios were calculated for each group. One-way analysis of variance revealed that in patients with upper GI bleeding, change ratios of white blood cell count and alkaline phosphatase were significantly higher than those in patients without, while change ratios of hemoglobin (Hb), total protein and albumin were significantly reduced. Logistic regression analysis demonstrated that the change ratio of Hb was significantly correlated with upper GI bleeding. Receiver-operator characteristic analysis revealed that an 18.7% reduction of Hb was the threshold value for the prediction of upper GI bleeding. In conclusion, the present study revealed that a ≥18.7% reduction in Hb over three months has predictive value for upper GI bleeding.