Night Time Use of Thiazide Diuretics for Improved Reduction in Stone Risk in Stone Formers With Elevated Urine Calcium

Inclusion Criteria: * Patients with recurrent calcium kidney stones (at least 2 episodes) and either a higher urine calcium excretion (urine Ca \>200 mg/d or \> 4 mg/kg body weight) or, * In patients who currently take a thiazide diuretic, a history of elevated urine calcium prior to medication use; * Also capable of signing consent and doing 24-hour urine collections repeatedly. Exclusion Criteria: * Patients with primary hyperparathyroidism, renal tubular acidosis, chronic kidney disease (serum creatinine \> 1.5 mg/dl), inflammatory bowel disease, gout, * Patients taking thiazides with a history of hypertension, * Patients with baseline systolic blood pressure less than 110mmHg