Inclusion Criteria:  > 18 years of age; on dialysis for > 3 months; pre-dialysis serum phosphate < 2.5 mmol/L and serum potassium < 6.3 mmol/L on most recent routine monthly blood test; urinary outputs of < 200 ml/day by self-report; being in their usual state of health  Exclusion Criteria:  history of diabetes mellitus history of parathyroidectomy history of calciphylaxis