The hypothesis formed suggests that insulin resistance developed in South Asians is explained, at least in part, by the presence of Vitamin D Deficiency (VDD). Therefore if the VDD is reversed/ 'normalised into target range' using Vitamin D therapy in individuals at risk of diabetes, then markers of insulin resistance should reduce from baseline values. However, current UK recommended doses of Vitamin D do not adequately replenish severe VDD, common in South Asians, back into the target range and therefore will not reduce insulin resistance markers. Therefore only higher pharmacological doses are able to replace severe Vitamin D deficiency adequately and improve insulin resistance markers.