When Vitamin D replacement is initiated in patients with history of urolithiasis, there will be higher incidence of hypercalciuria but with careful follow-up of these patients, hypercalciuria could be appropriately managed with thiazide diuretics so that the risk of newly diagnosed renal stones will be equivalent to control groups without Vitamin D replacements.the purpose of the study is to determine the effect of vitamin D replacement in patients with previous history of urolithiasis presenting to a tertiary stone clinic in terms of changes in 24-hour urine collection parameters and to evaluate the lithogenic effect of vitamin D replacement in terms of development of urolithiasis. Eighty-six eligible patients will be included in terms of having suboptimal vitamin D with history of calcareous urolithiasis and urinary calcium excretion <7.5 mmol/day. Patients will be randomly divided into 2 equal groups depending on whether they will receive vitamin D replacement with follow-up at 3, 6, 12, & 24 months.