Abstrakt Background Diabetes and periodontitis belong to the group of civilizational diseases, which are not associated with any specific bacterial or viral infection but with the rapid development of civilization and technological advances that affect comfort and quality of life. Civilizational diseases occur in highly developed and developing societies. Glycosylated hemoglobin A1c (HbA1c) is one of the standard indicators for the assessment of metabolic compensation in diabetes that reflects the risk of disease complications. One of the significant complications of diabetes that manifests in the oral cavity is gingival and periodontal inflammation, which is directly related to increased insulin resistance and worsened diabetes compensation. Factors influencing inflammation are the patient’s age, directly linked with fine motor skills when it comes to cleaning teeth, and patients’ awareness related to cause-and-effect relationship between dental hygiene, gingival and periodontal inflammation, and HbA1c testing during routine check-ups. Objectives To compare the relationship between gingival inflammation and metabolic compensation (HbA1c levels), depending on the patient’s age. Materials and methods The study involved 100 patients (50 adolescents and 50 adults, 42 M; 58 F) with type 1 diabetes. The study group was divided according to sex and age into 19 male adolescent patients (10–18 years old; mean age 15.5) and 23 male adult patients (19–45 years old; mean age 27.1). The mean duration of diabetes was 7 years in the group of adolescents and 11 years in the group of adults. The HbA1c levels and gingival index (GI) were measured in all patients. The obtained results were statistically analyzed. Results By comparing the study groups, higher HbA1c values were reported in the group of adolescents. HbA1c has been shown to correlate with the GI in adolescents and adults. Despite poorer compensation for diabetes (higher HbA1c), GI values were similar in adolescents and adults.