Objective: This study aimed to analyze doxorubicin and doxorubicinol levels in Dried Blood Spot (DBS) from 25 breast cancer patients who received doxorubicin in their therapeutic regiment. Methods: DBS samples were extracted by protein precipitation method and analyzed using Ultra Performance Liquid Chromatography tandem Mass Spectrometry (LC-MS/MS), with the Acquity UPLC BEH C18 Waters chromatography column (2.1 x 100 mm x 1.7 μm). The mobile phase consisted of 0.1% acetic acid (eluent A) and acetonitrile (eluent B) with gradient elution; the flow rate was 0.15 ml/min and runtime, 7 min. This method was linear within the concentration range of 10–200 ng/ml for doxorubicin and 4–100 ng/ml for doxorubicinol. Result: The analysis results showed that doxorubicin levels were in the range of 11.01 ng/ml to 93.75 ng/ml and doxorubicinol was 5.80 ng/ml to 58.57 ng/ml. Conclusion: Cumulative doses of all patients were in the range of 49.11 mg/m2to 303.70 mg/m2, which have cardiomyopathy incidence rates<4%.