This prospective, single-center, cross-sectional observational study aims to evaluate the association between serum 25-hydroxyvitamin D concentrations and lipid profile parameters among adults with obesity and established type 2 diabetes mellitus. A total of 160 participants will be recruited from an outpatient diabetes clinic in Cairo, Egypt. Each participant will undergo a single clinical, anthropometric, and laboratory assessment. No intervention or treatment will be assigned by the investigators.