Thiazide does not affect urine oxalate excretion.

Purpose: We assessed the effects of thiazide treatment on urine oxalate excretion in patients with kidney stones.

Materials And Methods: Of 537 patients (231 women), 209 (81 women) received thiazide for stone prevention. Urine oxalate was measured in 3, 24-hour urines before treatment, and in 1, 24-hour urine after 6 to 12 weeks of treatment. This was an observational cohort and treatment was not randomized.

Results: Urine oxalate increased in general. There was no difference in increase with or without thiazide, whether one considered simple t test comparisons or used ANOVA with pretreatment oxalate excretion as a covariate.

Conclusions: Thiazide administration exerts no measurable effect on urine oxalate excretion that can be detected in clinical practice.