ABSTRACT Background: Diabetes mellitus is a major public health problem that is responsible for morbidity and mortality. In Ethiopia diabetes is becoming a double burden due to urbanization. This problem is also critical in the Amhara region, Ethiopia. The study aimed to identify factors that affect the longitudinal fasting blood sugar and time to first remission among Type I diabetes mellitus patients on retrospective data recorded at Debre Tabor General Hospital; North-west Ethiopia. Method: The analysis of this study was based on the data collected from 210 selected patients. It consists of exploratory data analysis and fitting different models; those are the linear mixed model for the longitudinal part, Cox PH model for the survival part, and joint model for the longitudinal fasting blood sugar and time to first remission jointly. Kaplan-Meier survival estimate and Log-Rank test were used to compare the survival time. The two models' longitudinal and survival models were linked through their shared unobserved random effects. Result: From a total of 210 patients, about 68.1% got the event of first recovery and 31.9% were censored. The estimate of the association parameter (𝛼) in the joint model was -1.6608 and statistically significant (p-value<0.0001). The predictor variables; age, gender and other related disease were significantly associated with the two response variables jointly. Conclusion: Fasting Blood Sugar and the hazard for first remission was negatively associated. Thus, first remission was less likely to occur in patients with higher Fasting Blood Sugar. When evaluating the overall performance of both the separate and joint models in terms of Variability, goodness of fit and the statistical significance of the association parameters, the joint model performs better. Thus, the authors concluded that the joint model was preferred for the analysis of longitudinal and survival data. From the finding it is recommended as health professionals should record important variables like body mass index, feeding style, physical activity and further studies should be done in Type I diabetes mellitus by including such variables. Keywords: Fasting Blood Sugar, Time to first remission, linear mixed model, Cox proportional hazard model, Joint model