Introduction: Although monocyte-to-lymphocyte ratio (MLR), monocyte-to-HDL cholesterol ratio (MHR), and prognostic nutritional index (PNI) - have been associated with renal function in patients with diabetes mellitus, their repeatability and predictive value remain unclear. This study aims to evaluate the 6-month repeatability of these indices in diabetic patients using metrics such as the Intraclass Correlation Coefficient (ICC), compare their reliability indices, and investigate longitudinal associations between these indices with change in renal function. Material and methods: This longitudinal study included 51 patients diagnosed with type 2 diabetes mellitus, each assessed at two visits separated by 6 months. Inflammatory indices were calculated using standard formulas. The 6-month measurement repeatability of each inflammatory index was evaluated using the ICC. Longitudinal associations were based on changes in inflammatory indices and renal function over a 6-month period. Results: PNI showed good to excellent 6-month reliability (ICC(3,1) = 0.81; ICC(3,2) = 0.90), while MLR and MHR demonstrated moderate reliability. Baseline inflammatory indices were not independent predictors of eGFR at 6 months after adjustment for baseline renal function. In contrast, longitudinal analyses showed that changes in MLR and PNI were associated with changes in renal function, and ÄPNI was independently associated with ÄeGFR after adjustment. Conclusion: Inflammatory indices were reproducible over 6 months, with PNI showing the highest reliability. While baseline values had limited short-term predictive value, changes in PNI were independently associated with changes in eGFR, indicating longitudinal assessment of inflammatory-nutritional status in patients with T2DM.  Kulcsszavak: monocyte-to-lymphocyte ratio (MLR), monocyte-to-HDL cholesterol ratio (MHR), prognostic nutritional index (PNI), renal function, eGFR change, type 2 diabetes mellitus (T2DM)