Inclusion Criteria:  males and females age 18 or older documented cystinuria on prior 24-hour urine collection and/or stone analysis history of previous cystine kidney stones able and willing to provide consent  Exclusion Criteria:  prior diagnosis of diabetes mellitus (type I or type II) vulnerable populations including incarceration status anticipation of pregnancy during the study duration unable to give informed consent non-English primary language pregnancy, lactation, or child- bearing age without birth control devices serious illness likely to cause death within the next 5 years