PURPOSE OF REVIEW: To summarize recommendations from the 2011 US Institute of Medicine report (on vitamin D) and the new guideline from the US Endocrine Society with emphasis on treating and preventing vitamin D deficiency, including patients with inflammatory bowel disease and prior gastric bypass. RECENT FINDINGS: The US Institute of Medicine Recommended Dietary Allowance of vitamin D is 400 IU per day for children younger than 1 year of age, 600 IU per day for children at least 1 year of age and adults up to 70 years, and 800 IU per day for older adults. The US Institute of Medicine concluded that serum 25-hydroxyvitamin D [25(OH)D] of 20 ng/ml or more will cover the requirements of 97.5% of the population. The US Endocrine Society's Clinical Practice Guideline suggested that 400-1000 IU per day may be needed for children aged less than 1 year, 600-1000 IU per day for children aged 1 year or more, and 1500-2000 IU per day for adults aged 19 years or more to maintain 25(OH)D above the optimal level of 30 ng/ml. Patients with inflammatory bowel disease even in a quiescent state and those with gastric bypass malabsorb vitamin D and need more vitamin D to sustain their vitamin D status. SUMMARY: Difference in the recommendations from the US Institute of Medicine and the US Endocrine Society's Practice Guideline reflects different goals and views on current evidence. Significant gaps remain in the literature, and studies of vitamin D treatment assessing changes in outcomes at different 25(OH)D levels are needed.