As more human needs are addressed with technology, designing positive user experiences becomes increasingly important in developing effective health interventions. Designing successful user experiences for digital health interventions requires a deep understanding of patient challenges. In this paper, we attempted to identify challenges that diabetic patients face adhering to guideline-recommended care through persona development. Previous user experience research suggests that such an approach can be particularly beneficial in designing digital health interventions. We explain how we developed data personas from Electronic Health Records (EHR) and combined them with proto personas that were generated by a group of medical experts for the same patient population. Our results support previous research that suggests combining data and proto personas is beneficial for intervention design. Additionally, our results reveal that combining data and proto personas is likely to improve intervention design by addressing fairness issues that may result from the underrepresentation of certain populations in EHR datasets.