As many cells throughout the body possess the vitamin D receptor, adequate vitamin D levels may be essential for multiple physiologic functions. In recent years, vitamin D insufficiency has been linked to insulin resistance, inflammation, poor psychological health, obesity, type 2 diabetes, and cardiovascular disease - these are also commonly found in women with Polycystic Ovary syndrome (PCOS). We believe that vitamin D insufficiency contributes to insulin resistance, inflammation, and psychological distress in women with PCOS. These adverse effects may ultimately increase the risk for serious long-term complications in PCOS, including type 2 diabetes and cardiovascular disease. The key objectives of this research study are to determine the effects of vitamin D supplementation on insulin resistance, inflammation, mood and overall well-being in women with PCOS.