<qa>  What is the risk factor for kidney stones?The purpose of this pilot study is to determine the effect of various doses of vitamin D supplementation on vitamin D stores and calcium excretion in the urine in subjects with Thalassemia Major TM. Subjects with TM are routinely placed on vitamin D supplements because they frequently have osteoporosis a condition in which bone tissue thins and loses density and strength and low vitamin D stores. The amount of vitamin D supplementation that is required to raise vitamin D stores in optimal levels is not known in TM, and will be determined in this study. Finally, a recent study in TM has linked blood vitamin D levels to urine calcium excretion, which is a risk factor for kidney stones. Therefore, we want to determine changes in calcium excretion with various vitamin D doses and with increasing vitamin D stores. We plan to test 3 doses of vitamin D for 3 months in children and adults with TM. Changes in vitamin D blood levels and urinary calcium will be determined. The results of this pilot study will be used in future studies that will examine the effect of various doses of vitamin D supplementation in the treatment of osteoporosis in TM. 