262 & & Adults 51 to 70 years of age: 10 µg/d, or 400 IU Adults older than 71 years of age: 15 µg/d, or 600 IU. These recommendations are based on the amount of vitamin D that is needed to maximally suppress PTH (1– 84) secretion [22], but there is no consensus, as some investigators advocate that the 25(OH)2D level needed to maximally suppress PTH is 30 to 44 ng/mL [23]. The current recommendation for vitamin D supplementation of 600 IU for men and women older than 71 years of age is not sufficient to bring the level of 25(OH)D to 30 to 32 ng/mL, which is the level needed to lower fracture risk. Given the need to reach 25(OH)D levels of at least 30 ng/mL, it is recommended that the supplementation be enough to achieve this level. The National Academy of Sciences has recommended that the safe upper limit of 25 (OH)D be 50 µg/d, or 2000 IU. Vitamin D is available in two forms: ergocalciferol, or D2 (the plant form), and cholecalciferol, or D3 (animal origin). Studies have found that vitamin D3 increases serum 25(OH)D more effectively than vitamin D2 [24]. Therefore, vitamin D3 is the preferred form for clinical use. In summary, vitamin D is important for the maintenance and function of the musculoskeletal system. As they age, or due to nutritional deficiencies, many men and women need supplementation to meet the daily requirements and maintain normal serum concentrations. The general con- sensus is that a 25(OH)D level of 20 ng/mL, or 75 nM or higher, along with adequate calcium intake is needed to lower fracture risk, maintain well-mineralized bone matrix tissue, and maintain adequate muscle strength and function. Most older adults will need to be supplemented with 800 to 1000 IU/d of vitamin D3 to reach this level. Treatment Options for Patients With Vitamin D Deficiency Physicians and health care providers have several options for treating vitamin D insufficiency or deficiency. A loading dose of vitamin D can rapidly increase 25(OH)D to the normal range, and in the clinic, we frequently prescribe 50,000 IU of vitamin D once per week for about 8 weeks [23]. In our experience, the vitamin D levels often decline without maintenance therapy, so we recommend vitamin D doses of 400 to 1000 IU/d or to continue the 50,000 IU of vitamin D2 every 2 to 4 weeks. It is important to evaluate patients with recurrent vitamin D deficiency for evidence of fat malabsorption, celiac disease, or renal disease, as these individuals may need treatment of their underlying medical condition and possibly a higher maintenance dose of vitamin D to maintain normal, sufficient levels. Curr Rheumatol Rep (2010) 12:259–263 Vitamin D and Systemic Lupus Erythematosus Patients Several recently published reports have indicated that a high percentage of individuals with systemic lupus eryth- ematosus have insufficient or deficient levels of 25(OH)D [25, 26]. In practice, rheumatologists may be treating these patients with vitamin D2 or D3 supplements to increase serum levels of 25(OH)D to greater than 30 ng/mL. Although several anecdotal reports note that raising the serum concentrations to more than 30 ng/mL is associated with improvement in musculoskeletal disease symptoms, a formal clinical study has not yet been completed, although the Immune Tolerance Network is conducting a study to evaluate the effect of raising 25(OH)D levels on parameters of autoimmunity and systemic lupus erythematosus activity. Until the results of this trial are published, this author suggests that replacement of 25(OH)D to levels greater than 32 ng/mL should maximize the absorption of calcium from the gastrointestinal tract with reasonable suppression of serum PTH levels. Conclusions Vitamin D is critical for bone and muscle function. At this time, serum levels of 25(OH)D should be maintained at 32 ng/mL until further research determines whether higher serum levels improve outcomes. Acknowledgment This work was supported by National Institutes of Health grants R01 AR043052 and K24 AR-048841 to Dr. Lane. Disclosure No potential conflict of interest relevant to this article was reported. Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which per- mits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. References Papers of particular interest, published recently, have been highlighted as: Of importance Of major importance 1. Dusso AS, Brown AJ: Mechanism of vitamin D action and its regulation. Am J Kidney Dis 1998, 32(2 Suppl 2):S13–S24. 2. Malabanan AO, Holick MF: Vitamin D and bone health in postmenopausal women. J Womens Health (Larchmt) 2003, 12:151–156. 3. Lips P: Vitamin D deficiency and secondary hyperparathyroidism in the elderly: consequences for bone loss and fractures and therapeutic implications. Endocr Rev 2001, 22:477–501.