Abbreviations: MMAS-8, Morisky Medication Adherence Scale-8; OR, odds ratio; CI, confidence interval; AOR, adjusted odds ratio; BMI, body mass index; HbA1c, glycated hemoglobin; NE, not estimated; ID, Iraqi Dinar; OD, once daily; BID, twice daily; TID, three times daily; HTN, hypertension; IHD, ischemic heart disease; T2D, type 2 diabetes; DPP4i, dipeptidyl peptidase-4 inhibitor; SGLT2i, sodium-glucose cotransporter-2 inhibitor; SU, sulfonylurea; T2D, type 2 diabetes; TZD, thiazolidinedione; GI, gastrointestinal. The gene discussed is DPP4; the disease is type 2 diabetes mellitus.