Personalized health apps have become increasingly popular among young adults in Lagos, Nigeria, as a tool for self-care and management of chronic conditions. A mixed-methods approach combining quantitative data from app usage logs with qualitative feedback surveys was employed. User interaction metrics were analysed using a regression model to predict adherence rates, while thematic analysis of qualitative feedback identified key themes affecting engagement and effectiveness. The adoption rate of personalized health apps among young adults in Lagos was found to be 45%, with users showing significant interest in features related to symptom tracking (32%) and medication management (29%). The longitudinal feedback indicated that app-based interventions can enhance self-care behaviors, particularly when they are tailored to user needs and preferences. Future studies should explore the long-term effects of these apps on health outcomes and consider integrating community support mechanisms into app design. Personalized Health Apps, Young Adults, Self-Care Behaviors, User Interaction Metrics, Lagos Treatment effect was estimated with $\text{logit}(p_i)=\beta_0+\beta^\top X_i$, and uncertainty reported using confidence-interval based inference.