Abstract: Objective To evaluate the degree and characteristics of interference by calcium dobesilate in urinary creatinine measure-ment. MethodsUrine samples were colected from the patients receiving calcium dobesilate. The concentration of calcium dobesilate in urine samples was determined by liquid chromatography-tandem mass spectrometry(LC-MS/MS）. In accordance with the CLSI EP07-A3 guideline，specimens with urinary creatinine concentrations 6.0,9.0,13.0, 18.0,and 22.0 mmol/L were selected. A paired-difference experiment was conducted to confirm the interference from calcium dobesilate in urinary creatinine determination. Subse-quently，a dose-response experiment was performed using a series of calcium dobesilate concentrations(O,250，50o,1 125,2 250,3 375, and 4 500 mg/L) as interfering agents to evaluate the interference efect on creatinine measurement. Results Twenty-two 24-hour urine samples and 50 spot urine samples were collected from the patients taking calcium dobesilate. The calcium dobesilate concentrations ranged from 76 to 738 mg/L(median: 243,interquartile range[161 to 328]mg/L) in 24-hour urine samples and 60 to 2 236 mg/L (median； 370,interquartile range[195 to 667]mg/L) in spot urine samples. The paired difference testing showed that 4 500mg/L calcium dobesilate caused a 45.6% to 59.4% reduction in urinary creatinine measurements across the five concentration levels,all of which exceeded the maximum allwable error （10.0%). The doe-response experiment showed that negative interference effect on urine creatinine detection increased progressively with increasing calcium dobesilate concentration in urine samples. Conclu-sionCalcium dobesilate was found to cause a significant decrease in sarcosine oxidase-based urinary creatinine determination results,with thedegree of interferenceexhibiting concentration-dependence.Clinical laboratoriesshould fullyrecognizethisinterferenceeffect.For the patients taking this medication,it is recommended to use the reagent kits that are resistant to interference from calcium dobesil-ate or to collect urine samples after a washout period of at least 48 hours following the drug cessation.