AIM:To establish the frequency of hyperphosphate-mia following the administration of sodium phosphate laxatives in low-risk patients. METHODS:One hundred consecutive ASAⅠ-Ⅱindividuals aged 35-74 years,who were undergoing colonic cleansing with oral sodium phosphate(OSP) before colonoscopy were recruited for this prospective study.Exclusion criteria:congestive heart failure, chronic kidney disease,diabetes,liver cirrhosis,intestinal obstruction,decreased bowel motility,increased bowel permeability,and hyperparathyroidism.The day before colonoscopy,all the participants entered a 24-h period of diet that consisted of 4 L of clear fluids with sugar or honey and 90 mL(60 g)of OSP in two 45-mL doses,5 h apart.Serum phosphate was measured before and after the administration of the laxative. RESULTS:The main demographic data(mean±SD) were:age,58.9±8.4 years;height,163.8±8.6 cm; weight,71±13 kg;body mass index,26±4;women, 66%.Serum phosphate increased from 3.74±0.56 to 5.58±1.1 mg/dL,which surpassed the normal value (2.5-4.5 mg/dL)in 87%of the patients.The highest serum phosphate was 9.6 mg/dL.Urea and creatinine remained within normal limits.Post-treatment OSP se-rum phosphate concentration correlated inversely with glomerular filtration rate(P<0.007,R 2=0.0755),total body water(P<0.001,R 2=0.156)and weight(P< 0.013,R 2=0.0635). CONCLUSION:In low-risk,well-hydrated patients, the standard dose of OSP-laxative-induced hyperphos-phatemia is related to body weight. AIM: To establish the frequency of hyperphosphate-mia following the administration of sodium phosphate laxatives in low-risk patients. METHODS: One hundred consecutive ASA I-II individuals aged 35-74 years, who were undergoing colonic cleansing with oral sodium phosphate (OSP) before colonoscopy were recruited for this prospective study. Excage criteria: congestive heart failure, chronic kidney disease, diabetes, liver cirrhosis, intestinal obstruction, decreased bowel motility, increased bowel permeability, and hyperparathyroidism. h period of diet that consisted of 4 L of clear fluids with sugar or honey and 90 mL (60 g) of OSP in two 45-mL doses, 5 h apart.Serum phosphate was measured before and after the administration of the laxative. RESULTS Height: 163.8 ± 8.6 cm; weight, 71 ± 13 kg; body mass index, 26 ± 4; women, 66% .Serum phosphate increased from 3.74 ± 0.56 to 5.58 ± 1.1 mg / dL , which surpassed the normal value (2.5-4.5 mg / dL) in 87% of the patients. highest serum phosphate was 9.6 mg / dL. Urea and creatinine remained within normal limits. Post-treatment OSP se-rum phosphate concentration correlated inversely with glomerular filtration rate (P <0.007, R2 = 0.0755), total body water (P <0.001, R2 = 0.156) and weight hydrated patients, the standard dose of OSP-laxative-induced hyperphos-phatemia is related to body weight.