Objectives: To determine the frequency of diabetes mellitus among patients diagnosed with lichen planus. Material and Methods: A six-month descriptive cross-sectional study was conducted at the Khyber Teaching Hospital after ethical approval. In this study, all patients diagnosed With Lichen Planus (LP) in the outpatient department who met the inclusion criteria were assessed. After a thorough examination, a phlebotomist collected 2 ml of venous blood from each patient for blood glucose level measurement at the hospital laboratory. Results: Among the 139 enrolled patients, 59.6% were male and 42.4% were female. The mean age was 44.66 years, ± 11.81 SD. The frequency of diabetes mellitus was 17.3% in the patient cohort. The mean random blood sugar (RBS) level was 242.17 mg/dl ± 26.29 SD in Lichen Planus patients with diabetes mellitus (DM) and 109.21 mg/dl ± 20.25 SD in LP patients without DM (P<0.001). 36.5% of patients with a history of steroid use had DM, compared to only 27.8% of those without (p <0.001). Conclusion: The study found the prevalence of diabetes mellitus in LP to be 17.3%, with a higher prevalence in patients who had a previous history of systemic steroid use.