Oxalate and Citrate in Humans - Response to Citrate

Inclusion Criteria:

Stone formers (SF):

* Age 18-70
* History of at least one calcium-based kidney stone

Non-stone formers (NSF):

* Age 18-70
* No history of kidney stone
* 24-hour urine oxalate within laboratory normal range (\<50 mg/day)

Exclusion Criteria:

History of primarily uric acid, cysteine, or struvite stones

History of severe acid-base abnormality, very low (less than 100 mg/day) or very high (greater than 1500 mg/day) urine citrate

Any controls or stone former (SF) participants who cannot stop diuretic medication or alkali supplementation for the course of the study period

Chronic kidney disease (glomerular filtration rate \<75 milliliters per minute per 1.73 square meters \[mL/min/1.73 m²\])

Non-stone formers (NSF) and stone formers (SF) with extreme levels of urine citrate will be excluded from this small initial study to reduce heterogeneity and remove focus from the extremes of citrate levels.