Background: T1D is a significant global health concern. It is indicated that a Vit D deficit increases the likelihood of developing T1D. The role of supplementations of Vit D are now up for discussion. Subjects & Methods: A prospective research was assessed how supplementation of Vit D affected young individuals with T1D. In this research, 60 children divided to two groups, 40 T1D children with a mean age of 7.9 years ±2.7 SD, and their levels of vit D less than 20ng/ml, and healthy 20 children participated in this study as control group. Chemiluminescence immunoassay was utilized to assess the serum Vit D levels of each sample. Serum Ca, PTH, Ph, ALP was evaluated; serum F.B.S., P.P.S. and HbAlc% levels. Supplementation was added by 4000 IU/ day Vit D for 3 months to patient's group only. Results: Before supplementation, blood levels of Vit D were considerably lower in patient gp. in comparison to the control gp. (9.3±1.4Vs 59.2 ± 18.7ng/ml p < 0.0001).

While after supplementation of Vit D, levels of Vit D were improved in contrast to that before (9.3± 1.4Vs 38.7±4.2ng/ml p < 0.0001). There was also improvement in the glycemic evaluated by HbAlc% and serum glucose after supplementation 10.5±1.3Vs 5.2±0.8% and 231.8±11.0 Vs 89.6±7.7mg/dl respectively p<0.0001) for HbAlc% and glucose before and after supplementation respectively. Conclusion: It would seem crucial to implement a global public health intervention which incorporates supplementation of Vit D in particular risk groups to prevent severe Vit D insufficiency.