After determining vitamin D deficiency and prescribing an eight-week course of weekly ergocalciferol (vitamin D2), when is the best time to reassess with a blood test? — KATHLEEN TREADUP, ANP, New Bedford, Mass.

Reassess levels after three months. Vitamin D is fat-soluble and can be toxic at >88 ng/mL. The Institute of Medicine published its new recommendations for Vitamin D and calcium intake last year. The recommendations are available, here (accessed February 15, 2011). — Rebecca H. Bryan, APRN, CNP, lecturer, family health nurse practitioner program, University of Pennsylvania School of Nursing, Philadelphia (149-4)