Background: Diabetes mellitus impacts tooth-supporting tissues and has complications, including the sixth most common disease, periodontitis. Gingival crevicular blood, which oozes during periodontal probing, can be used to measure blood glucose levels with a glucometer that enables frequent glucose monitoring for diabetic patients. Objectives: This study aimed to evaluate the blood glucose levels in diabetic and nondiabetic patients by the finger prick method and the gingival crevicular blood method. Methods: For the conduct of the study, 50 patients were selected from the outpatient Department of Oral Medicine and Radiology of Vinayaka Mission's Sankarachariyar Dental College in Salem, Tamil Nadu. The subjects were divided into two groups (group I - 25 type II diabetes and group II - 25 nondiabetes). Blood samples from a finger prick and gingival crevicular blood were analyzed for random blood glucose using a glucometer. Results: A strong positive correlation was observed in finger prick blood and gingival crevicular blood with values of 0.939 in the diabetic group and 0.730 in the nondiabetic group using Pearson's correlation. The comparison of finger prick blood and gingival crevicular blood in both groups was highly significant. Conclusion: Gingival crevicular blood offers a noninvasive, safe, simple, and inexpensive alternative chairside diagnostic method for measuring blood glucose levels. © 2023 Elsevier B.V., All rights reserved.