Ketogenic Diet is well studied and applied as a treatment in numerous nervous system diseases, such as epilepsy. However, KDs long term effect on the cells and the risk of potential insulin resistance are unclear. In this research, we aim to testify whether the usage of KD on patients with epilepsy would increase the risk of diabetes. In this research we firstly verified the cytotoxicity of the islet B cells which might be stimulated by the abundance of fats in the KD. We used a CCK-8 kit to conduct the experiment and obtained a result of higher IC50 values in the keto conditioned cells, which indicates that cells in keto face a higher cytotoxicity than cells in normal condition. Afterwards, we did both vivo and in vitro experiments on the rats. In the in vitro experiment, the islet cells in a keto-environment showed a higher apoptosis rate. In the in vivo experiment, Enzyme-linked immunosorbent assay (ELISA) was used to detect the insulin level and blood fat in plasma of rats. The result out of ELISA demonstrates a continuously decreasing level of insulin and lower body fat. In addition, oral glucose tolerance test (OGTT) was also used to find the blood sugar in the rats which came out as a result that the glucose metabolism has decreased. Although the experiments exhibit several side effects of KD, it might not be applicable to humans since we only had animal experiment. This research aims to reevaluate the benefits and side effects of application of KD to curing epilepsy.