ObjectiveThe main objective was to analyze unjustified discrepancies during the medication reconciliation process in patients admitted to the Hematology Service of our hospital and the pharmaceutical interventions. As a secondary objective, to detect possible points of the procedure to be perfected with a view to protocolizing the medication reconciliation process in hematological patients that adapts to the conditions of our center. MethodsCross-sectional observational pilot study carried out in a reference hospital in hematology for a population of 800,000 inhabitants. Adult inpatients admitted to the Hematology Service between August and October 2022 whose medication had been reconciled were included. The main variables were: number and type of unjustified discrepancy, proposed pharmaceutical intervention, and acceptance rate. Results36 conciliation processes were analyzed, 34 admissions and 2 intrahospital transfer. 58.3% of the patients presented at least one unjustified discrepancy. 38 unjustified discrepancies were detected, with an acceptance of pharmaceutical interventions of 97.4%. The most common types of discrepancy were medication omission (56.8%) and drug interaction (24.3%). The most frequent pharmaceutical interventions were reintroducing medication (48.6%) and treatment discontinuation (16.2%). Polypharmacy and chemotherapy multiplied by 4 the probability of presenting drug interactions. ConclusionsThe most common unjustified discrepancies in the medication reconciliation process in hospitalized hematology patients are: Medication omission and drug interactions. The reintroduction of medication and suspension of the prescription are the most frequent accepted pharmaceutical interventions. Polypharmacy is related to an increase in unjustified discrepancies. The factors that promote the appearance of interactions are admissions to receive chemotherapy treatment and polypharmacy. The main point of improvement detected is the need to create a circuit that allows conciliation to be carried out on discharge. Medication reconciliation contribute to improving patient safety by reducing medication errors.