Aim: We assessed the feasibility of using hematological parameters (such as hemoglobin and reticulocyte mRNA) in dried blood spot (DBS) samples to test athletes for doping and to improve patient care. Methods: Hemoglobin and erythropoiesis-related mRNAs were measured in venous blood and DBSs from both healthy athletes and hemodialysis patients. Results: We accurately measured hemoglobin changes over time in both venous blood and DBS samples. Combining hemoglobin and mRNA analyses, we detected erythropoietin injection in DBSs more sensitively and with higher efficiency by using the DBS OFF-score than by using the athlete biological passport OFF-score. Conclusion: DBS-based measurements are practical for calculating hemoglobin levels and athlete biological passport OFF-scores. This approach may help detect blood doping and help predict patient response to EPO.