The finger stick blood(FSB) and the gingival crevicular blood(GCB) of patients with diabetes and periodontitis are highly consistent in blood glucose concentration, as well as the glycosylated hemoglobin(GHbA1c) level in GCB and FSB. The incidence of diabetes accounts for about two-thirds of people with periodontal diseases. However, diabetes mellitus is not diagnosed in many patients suffering from periodontal diseases. Dental clinics might perform periodic treatment of oral diseases, but a dental hospital is an important place for diabetes screening. Regular screening for diabetes mellitus is crucial for early diagnosis and preventive intervention. Periodontists may encounter an increasing number of patients who have not been diagnosed with diabetes mellitus in the regular periodontal maintenance. To optimize the therapeutic effects, early diagnosis and intervention can prevent the development of complications and help in developing treatment programs. Periodontal probing is one of the most important and common diagnostic methods for periodontitis. GCB can be collected as a source to analyze the levels of blood glucose and GHbA1c. Compared with the conventional use of FSB, GCB provides more advantages because it is minimally invasive, simple, accurate, timely, and safe. Can avoid to use the FSB acupuncture when testing blood sugar levels take blood cumbersome operation, fear and pain in patients with significant defects.