A new study published in Clinical Biochemistry evaluated the accuracy of creatinine and cystatin C (cysC) equations to estimate glomerular filtration rate (GFR) in type-2 diabetes mellitus (DM) patients and healthy adults. This was a case-control study which recruited 84 patients with type-2 DM and 100 healthy adults with measured GFR (mGFR) ≥ 60mL/min/1.73m². Among the participants, 66% of the healthy individuals were females, aged 38±14 years, who presented mGFR 112±19mL/min/1.73m² and eGFR by CKD-EPI, CKDEPI-CC, CKDEPIcysC and CAPA equations, 108±17, 102±15, 97±16 and 93±16mL/min/1.73m2, respectively. Whereas, the DM group comprised 50% females, aged 59±19 years and presented mGFR 104±27 and eGFR 87±19, 80±18, 74±20 and 73±18mL/min/1.73m², respectively. Moreover, all equations significantly underestimated mGFR, apart from creatinine-based CKD-EPI in the healthy group. While the performance was considerably worse for GFRs above 120mL/min/1.73m². The findings of this study indicated that in both healthy and type-2 DM patients, cystatin C-based equations, including the combined CKD-EPI creatinine-cystatin equation, failed to improve the accuracy of GFR estimation, especially for normal and high normal GFR values.