Although renal calcium crystal deposits (nephrocalcinosis) may occur in acute phosphate poisoning as well as type 1 renal tubular acidosis (RTA), hyperphosphatemic hypocalcemia is common in the former while normocalcemic hypokalemia is typical in the latter. Here, as a unique coexistence of these two seperated clinical entities, we report a 30-yr-old woman presenting with carpal spasm related to hypocalcemia (ionized calcium of 1.90 mM/L) due to acute phosphate poisoning after oral sodium phosphate bowel preparation, which resolved rapidly after calcium gluconate intravenously. Subsequently, type 1 RTA due to Sjögren's syndrome was unveiled by sustained hypokalemia (3.3 to 3.4 mEq/L), persistent alkaline urine pH (> 6.0) despite metabolic acidosis, and medullary nephrocalcinosis. Through this case report, the differential points of nephrocalcinosis and electrolyte imbalances between them are discussed, and focused more on diagnostic tests and managements of type 1 RTA.