Inclusion Criteria:

• * Mentally competent adults, able to read and comprehend the consent form
• * Body Mass Index (BMI) between 18.5 and 50 kg/m2
• * Acceptable 24 hour urine collections (judged on screening)
• * for non-stone formers, good health as judged from a medical history, reported medications, and a complete blood metabolic profile, baseline urinary oxalate excretion \< 40 mg/day
• * for kidney stone formers: first time or recurrent CaOx stone former with stone event within the prior 3 years. Composition of most recent stone (if known) \> 50% calcium oxalate, without uric acid component.

Exclusion Criteria:

• * History of any hepatic, bowel, or endocrine disease or other condition that may influence the absorption, transport or urine excretion of ions
• * Abnormal urine chemistries or blood metabolic profiles
• * Poor 24 hour urine collections completed during screening, judged by 24 hour urine creatinine excretion (indicative of not collecting all urine in the 24 hour period)
• * Pregnancy, intention to become pregnant in the near future, or lactation
• * Aged \<18 or \>75 years
• * BMI \<18.5 or \>50 kg/m2