Thiamine deficiency has been documented to be prevalent in patients with diabetes mellitus, and correction of thiamine deficiency in this population may provide beneficial effects in several cardiometabolic parameters, including prevention of impending complications secondary to chronic hyperglycemia. In this interventional study, we aim to determine whether thiamine supplementation is associated with cardiometabolic improvements in patients with diabetes mellitus type 2 (DMT2). A total of 86 subjects (60 DMT2 and 26 age- and BMI-matched controls) were included and were given thiamine supplements (100 mg/day) for six months. Anthropometrics and metabolic profiles were measured routinely. Serum thiamine and its derivatives were measured using high performance liquid chromatography. In all groups, there was a significant decrease in total cholesterol after three months ( p = 0.03) as well as in HDL cholesterol after six months of thiamine supplementation ( p = 0.009). Significant improvements were also observed in the mean serum levels of creatinine ( p = 0.001), as well as thiamine and its derivatives in both serum and urinary levels across follow-up visits ( p-values 0.002 and <0.001, respectively). In the DMT2 group, improvements were observed in lipid profile (mean serum LDL and total cholesterol with ^-values 0.008 and 0.006, respectively), serum thiamine ( p < 0.001), TMP ( p < 0.001), TDP ( p < 0.001), urinary thiamine ( p < 0.001) and serum creatinine ( p < 0.001). Thiamine supplementation is a promising adjuvant therapy for patients with DMT2. Longer clinical trials are needed to determine its protective effect in DMT2 complications.