BACKGROUND Diabetes mellitus (DM) is undiagnosed in approximately 1/2 of the patients actually suffering from the disease. In addition, the prevalence of DM is more than 2x as high in patients with periodontitis when compared to periodontally healthy subjects. Thus, a high number of patients with periodontitis may have undiagnosed DM. OBJECTIVE The purpose of this pilot study was to evaluate, whether blood oozing from gingival tissues during routine periodontal examination can be used for determining glucose levels. 32 non-diabetic and 13 diabetic patients with moderate to severe periodontitis were enrolled and subjected to routine clinical periodontal examination. Periodontal pocket probing was performed using a standard force. Blood oozing from gingival tissues of anterior teeth following periodontal pocket probing was collected with the stick of a glucose self-monitoring device (Elite(R) 2000, Bayer Diagnostics GmbH, Munich). As control, fingerstick capillary blood was taken. Statistical analysis was performed by Pearson's correlation coefficient. RESULTS The patient blood glucose levels ranged from 3.57 mmol/l to 18.01 mmol/l and the values of blood samples taken from gingiva or finger tip showed a very high intrapatient correlation (r=0.98; p<0.0001). CONCLUSIONS The results suggested that blood oozing during routine periodontal examination may be used for diabetes mellitus screening in a dental office setting.