Adjusting for differences in CKD-EPI eGFR, gender, age and BMI revealed a significantly lower cystatin C level in HNF1A-MODY compared with T1DM, T2DM and ND groups (0.197 mg/l less than T1DM, 95% CI: 0.138–0.257, p < 0.0001; 0.148 mg/l less than T2DM, 95% CI: 0.083–0.214, p < 0.0001; and 0.069 mg/l less than ND, 95% CI: 0.06–0.133, p < 0.03). Here, CST3 is linked to type 1 diabetes mellitus.