Anticoagulants represent a main source of medication errors (MEs) and complications that have catastrophic implications, posing an obligation on health care providers to assess anticoagulant-related MEs and factors affecting their occurrence.This study investigates the occurrence and severity of prescribing MEs in patients on anticoagulants and explores their potential predictors.Methods: This study was a prospective cohort study in a tertiary hospital on 116 patients with a total of 2166 anticoagulant doses.Results: Forty-four percent of prescribed anticoagulant doses resulted in MEs with low molecular weight heparin (LMWH) and unfractionated heparin (UFH) causing 61% and 34%, respectively, of the total MEs. More than 50% of all MEs were incorrect doses (high and low) shared between heparin and tinzaparin. The highest severity of error was Category D followed by Category F and Category C. A Poisson regression analysis model revealed that female (incidence rate ratio [IRR] 1.32, 95%