Purpose: To compare the HbA1c levels in nondiabetic subjects with periodontitis and periodontally healthy controls and to evaluate the effect of nonsurgical periodontal therapy on the glycaemic control in nondiabetic subjects with periodontitis. Materials and Methods: A total of 220 nondiabetic subjects between 35 and 60 years old were selected and divided into two groups: group A (case group), comprised of subjects with chronic periodontitis, and group B (control group), comprised of subjects with healthy periodontium. Periodontal clinical parameters (plaque index, modified sulcular bleeding index, probing depth and clinical attachment level) were used to assign the subjects into the respective groups. The HbA1c level was estimated for both groups using a commercially available kit. Subjects in group A underwent nonsurgical periodontal therapy in two to four sessions along with oral hygiene instructions. The periodontal parameters and HbA1c levels were again evaluated in the test group three months following periodontal therapy. Results: The HbA1c levels were higher in the case group (A) than the control group (B). Three months following periodontal therapy in group A, there was improvement in periodontal parameters. The HbA1c levels decreased significantly from baseline to 3 months. Conclusion: The results of this study found chronic periodontitis to be associated with a significant increase in glycosylated haemoglobin levels in nondiabetic periodontitis subjects. Furthermore, with improvement of periodontal status, the glycaemic levels return to near normal values. Keywords: chronic periodontitis, diabetes mellitus, glycosylated haemoglobin, HbA1c%, nonsurgical periodontal therapy, prediabetic state