Background : PTEN, through PI3K/Akt suppression, inhibits insulin receptor signaling, and hence cellular glucose uptake. Vitamin D (VD), through its receptor VDR, regulates Ca+2 channel flux, which is essential for pancreatic insulin secretion, and also has a prosteatotic effect as a result of activating lipogenic routes and suppression of lipid β-oxidation in the liver. Therefore, we probed for potential molecular interactions of PI3K/Akt and VD-dependent pathways on glucose and lipid metabolism. Methods : We used inducible pan PTEN and VDR single gene KO and double KO (DKO) mouse models. After a single Tamoxifen injection (25mg/kg), 4 groups of mice were studied: DKO, PTEN-KO, VDR-KO and control (CNT)). In vivo glucose tests were performed (glucose tolerance test, pyruvate tolerance test, glucose behavior and blood glucose). We measured insulin secretion by isolating pancreatic islets and incubating them with 5mM glucose. Organs and blood were harvested for histological and molecular biology studies. Several strategies were used to increase survival of the animals (increased glucose delivery to the brain, sucrose in water, bicarbonate in water, and high fat diet). Results : DKO mice died prematurely (32% of survival after 2 months vs 74% in PTEN-KO mice and 100% in VDR-KO and CNT mice) and did not survive short fasting periods, showing rapid signs of lethargy and nonresponsiveness. PTEN deficiency induced severe hypoglycemia, both in a postprandial and starving state, and hypoinsulinemia was observed both in PTEN-KO and DKO mice. However, glucose supplementation did not enhance DKO survival. In addition, PTEN ablation promoted defects in insulin secretion that were enhanced by the absence of VDR. Furthermore, PTEN-KO mice had down-regulated renal glucose transporter expression that could explain the mild glycosuria, which was further exacerbated after deletion of VDR. In liver, PTEN deletion induced a pre-steatotic state, which was attenuated by co-ablation of VDR in DKO mice. Moreover, we detected delayed hepatic gluconeogenesis activation in PTEN-KO and DKO mice. With regard to lipid and ketone metabolism, we found that although PTEN-KO and DKO mice ate more, they used ketone bodies even when they were not food-restricted. Moreover, treating DKO mice with high fat diet increased their survival. Finally, we observed that PTEN deletion delayed β-oxidation and decreased lipogenesis, and this was aggravated by deletion of VDR. Conclusion : Absence of PTEN strongly impairs glucose and lipid metabolism and VDR deletion exacerbates the phenotype. If we extrapolate our DKO mice results to humans, we propose that VD levels should be clinically monitored in subjects with type 1 diabetes mellitus, particularly in those that have a lean phenotype and recurrent episodes of severe hypoglycemia. Dietary supplementation with VD may have therapeutic metabolic benefits in these individuals.