Vitamin D deficiency is the most common nutritional deficiency worldwide, however uncertainty persists regarding the benefits of vitamin D supplementation. Vitamin D is essential for calcium homeostasis, and has been linked to falls and fractures in older people. There are numerous risk factors for vitamin D deficiency, chief among them old age. Studies of vitamin D supplementation have given mixed signals, but over all there is evidence of benefit for those with risk factors for deficiency. International guidelines recommend vitamin D target levels of >25 to >80¿nmol/l, best achieved by a daily dose of 800-1000¿IU. Large bolus doses should be avoided. There are still unanswered questions regarding vitamin D supplementation and target levels. There is need for well designed and powered trials to achieve consensus.