Objective: Diabetes mellitus is a systemic condition associated with periodontitis. The study was conducted to evaluate the effectiveness of gingival crevicular blood (GCB) for diabetic screening as a chair–side method. Method: The subjects were divided into two groups: subjects with moderate to severe chronic periodontitis and healthy or gingivitis subjects. Estimation of GCB and Capillary finger blood (CFB) glucose levels was carried out using a self–monitoring glucometer and analyzed to find correlation within the groups. Results: The correlation between the GCB and CFB glucose readings for group I were strong (0.74). However, correlation between the readings for group II was weak (–0.295). Conclusion: GCB can be used for diabetic screening as chair–side method and can be encouraged in patients with chronic generalized periodontitis to facilitate early diagnosis and treatment.