Background: Erythroid stimulating agents (ESAs) have pleiotropic effects, and in animal and human studies those exposed to high erythropoietin had lower blood glucose. Objective: To determine the association between ESA and glucose in anemia-treated patients with myelodysplastic syndromes (MDS) or multiple myeloma (MM). Patients and Methods: Patients’ glucose levels were compared while on to while off ESA, and all served as their own controls. To test the association between ESA and blood glucose, we employed a linear mixed model, accounting for variability in the number of measurements for each patient. Results: Charts of 20 patients were reviewed. Mean age was 77 ± 9.8 years (range 50–91). Thirteen patients had MDS, and 8 had MM (1 with both). Glucose (mean ± standard error of the mean) was 116.38 ± 5.21 mg/dL without ESA, as opposed to 105.64 ± 5.11 mg/dL with ESA (p < 0.0001). The 3 diabetic and 5 steroid-treated patients also demonstrated reduced glucose by approximately 19 mg/dL with ESA (p = 0.003 and p = 0.0001, respectively). There was no difference in collective hemoglobin levels between the 2 groups. Conclusion: ESA treatment for anemia is associated with lower blood glucose in hematologic patients. In those who also have diabetes mellitus, ESA might contribute to glucose control, and even to hypoglycemia. Glucose monitoring is thus advised. Further studies with both diabetic and nondiabetic patients are needed to clarify this association and underlying mechanisms.