Background: This study was conducted to assess the comparison between dosages and plasma concentrations of dexmedetomidine in clinically ill patients.Material and methods: Using a single-blind method, ultra performance liquid chromatography coupled with tandem mass spectrometry was used to measure the plasma dexmedetomidine concentrations of 65 samples taken from 50 patients who had been in an intensive care unit for a period of two months. Additionally, the correlation coefficient between dosages and plasma concentrations was calculated. The criteria for exclusion included individuals who were less than 15 years old and samples acquired from patients whose dosage of dexmedetomidine was altered within a period of three hours. SPSS software was used for evaluation of the results. Results:Among the patients, 30 (60%) of the 50 were given dexmedetomidine at a dosage range of 0.22–0.85μg/kg/h. Furthermore, in the 50 samples that were administered dexmedetomidine, this occurred for a median length of 17.9 hours, with a range that extended from three to eighty-seven hours. Dexmedetomidine plasma concentrations ranged from 0.25 to 2.58 ng/ml throughout the investigation. Conclusion:Patients were able to achieve an effective concentration of dexmedetomidine ranging from 0.25 to 2.58 ng/ml by administering a dosage of 0.22 to 0.85μg/kg/h.