he bowel cleanse for the colonoscopy operation should be conducted using an effective, safe, and tolerable by the patients. However, matching all these criteria is not always possible for every patient. Sodium phosphate-a cleansing agent for colonoscopy, should be carefully administered in the cases where the body fluid/electrolyte balance may be offset; such as of chronic kidney failure, heart failure, old age, diuretic use, angiotensin-converting enzyme (ACE) inhibitor and angiotensin receptor blockers (ARBs) use. It is not always possible to foresee the possible adverse effects of the cleansing agents on healthy individuals. We review the case of severe hypocalcemic tetany that developed in a female patient after the oral administration of two doses of 45 mL sodium phosphate, together with the possible causes. CASE REPORT The 38-year-old female patient applied with complaints of stomach ache, difficulty in defecation and changes in bowel habits that had been continuing for six months. The patient had a family history of colon cancer developing under the age of 40, thus she was referred for a colonoscopy examination. On the day of the colonoscopy, the patient noted that she did not feel well; she had a tingling sensation all over the body, but especially in the legs. Subsequently, the colonoscopy was canceled, and the patient