Abstract: Platinum analog has a potential cytostatic effect and causing nephrotoxicity or a decrease in kidney function. This study used creatinine level to assess kidney function that are carried out routinely before the patient starts the chemotherapy cycle. This study aimed to determine the differences in creatinine levels before and after platinum-based chemotherapy. This an analytical study used retrospective cohort design with a total sample of 70 people according to inclusion criteria. The result showed a median creatinine level of breast cancer patients before and after platinum-based chemotherapy is 0,63 mg/dL and 0,75 mg/dL. Wilcoxon test results obtained”p=0,000 (p <0.05), considered as a significant difference between creatinine level before and after platinum-based chemotherapy in breast cancer patients period January 2018-June 2019 in Ulin Hospital Banjarmasin, but the change of creatinine levels remain in the normal range. Keywords: platinum, based” chemotherapy, creatinine” levels, breast cancer” Abstrak: Analog platinum memiliki efek sitostatika poten dan efek samping nefrotoksisitas atau penurunan fungsi ginjal. Penilaian fungsi ginjal menggunakan parameter kadar kreatinin yang dilakukan secara rutin sebelum pasien memulai siklus kemoterapi. Penelitian bertujuan untuk mengetahui perbedaan kadar kreatinin sebelum dan sesudah kemoterapi berbasis platinum. Ini adalah penelitian observasional analitik dengan pendekatan Kohort Retrospektif dengan subjek penelitian 70 orang sesuai kriteria inklusi. Didapatkan median kadar kreatinin sebelum dan sesudah kemoterapi berbasis platinum sebesar 0,63 mg/dL dan 0,75 mg/dL. Uji Wilcoxon menunjukkan nilai p=0,000 (p<0,05), disimpulkan terdapat perbedaan bermakna kadar kreatinin sebelum dan sesudah kemoterapi berbasis platinumpada pasien kanker payudara periode Januari 2018-Juni 2019 di RSUD Ulin Banjarmasin meskipun perubahan kadar kreatinin masih dalam rentang normal. Kata-kata kunci: kemoterapi berbasis platinum, kadar kreatinin, kanker payudara