We report herein an adult case of chronic kidney disease (CKD) associated with diabetes. The patient had been treated with insulin injection for diabetes 10 years ago. At the time of his first visit to our division for further examinations, we diagnosed him as CKD: cause (C) diabetes; glomerular filtration rate (GFR) (G) G5 (estimated [e] GFR, 10.2 mL/min/1.73 m2; serum creatinine of 4.90 mg/dL); and albuminuria (A) A3 (2.62 g/gCr) by the Japanese Society of Nephrology (JSN) CGA classification. Because he had complained of severe constipation and kidney function, i.e., eGFR was not improved by previous medications, we added on a minimal dosage (2 g/day) of AST-120 (Kremezin®; ordinary dose 6 g/day). After 3 months of AST-120 therapy, eGFR was increased to 17.8 mL/min/1.73 m2 (serum creatinine of 2.90–2.72 mg/dL). Although the patient used some laxative products, he could not continue to take Kremezin and completely stopped 8 months after starting this drug. Kidney function then abruptly declined and progressed to end-stage kidney disease (ESKD). In June 2017, he was introduced to hemodialysis. It appears that the adherence of Kremezin is very important for inhibiting the progression to ESKD for patients with CKD with diabetes.