Background: The effect of glycemic control on severity of periodontal inflammatory parameters in patients with prediabetes is unknown. The aim of the present study is to assess the effects of glycemic control on self-perceived oral health, periodontal parameters, and marginal bone loss (MBL) in pa-tients with prediabetes. Methods: A total of 303 individuals were included. Hemoglobin A1c (HbA1c) and fasting blood glu-cose levels (FBGLs) were recorded. Participants were divided into three groups: 1) group A: 75 patients with prediabetes (FBGLs = 100 to 125 mg/dL [HbA1c 5%]); 2) group B: 78 individuals previously con-sidered prediabetic but having FBGLs <100 mg/dL (HbA1c <5%) resulting from dietary control; and 3) control group: 150 medically healthy individuals. Self-perceived oral health, socioeconomic status, and education status were determined using a questionnaire. Plaque index (PI), bleeding on probing (BOP), probing depth (PD), and clinical attachment loss (AL) were recorded. Premolar and molar MBLs were measured on panoramic radiographs. Results: Periodontal parameters (PI, BOP, PD, and AL) (P <0.01) and MBL (P <0.01) were worse among individuals in group A than those in group B. Self-perceived gingival bleeding (P <0.001), pain on chewing (P <0.001), dry mouth (P <0.001), and oral burning sensations (P <0.05) were worse among patients in group A than those in group B. There was no difference in periodontal parameters, MBL, and self-perceived oral symptoms among patients with prediabetes in group B and healthy controls. Conclusions: Self-perceived oral health, severity of periodontal parameters, and MBL are worse in patients with prediabetes than controls. Glycemic control significantly reduces the severity of these parameters as well as the state of prediabetes in affected individuals. J Periodontol 2014;85:234-241. KEY WORDS Alveolar bone loss; hyperglycemia; periodontal disease; prediabetic state.