Objective: We performed a post hoc analysis of a multicenter, prospective randomized controlled study – the SALSA (Efficacy and Safety of Rapid Intermittent Correction Compared With Slow Continuous Correction With Hypertonic Saline In Patients With Moderately Severe or Severe Symptomatic Severe Hyponatremia) trial in 178 patients above 18 years old with symptomatic hyponatremia (mean age 73.1 years, mean serum sodium (sNa) concentrations 118.2 mmol/L). Overcorrection was defined as an increase in sNa by >12/18 mmol/L within 24/48 hours at any time. Methods: Thirty-seven of 178 patients experienced overcorrection (20.7%). Overcorrection was independently associated with initial sNa level (≤ 110 mmol/L: 7 points; 110-115 mmol/L: 4 points; 115-120 mmol/L: 2 points; 120-125 mmol/L: 0 point). chronic alcoholism (7 points), severe symptoms of hyponatremia (3 points), and initial potassium level (< 3.0 mmol/L: 3 points). The NASK score was derived from these four risk factors for overcorrection (hypoNatremia, Alcoholism, Severe symptoms, and hypoKalemia) and was significantly associated with overcorrection (odds ratio 1.41, 95% CI 1.24 to 1.61; P <.001) with good discrimination (area under the receiver operating characteristic curve 0.76, 95% CI 0.66 to 0.85; P <.001). The AUROC value of the NASK score was statistically better comparing to those of each risk factor. Each risk factor contributed to overcorrection by diuresis. Results: In treating patients with symptomatic hyponatremia, individuals at high risk of overcorrection were predictable using a novel risk score summarizing baseline information. Conclusions: Objective: Overcorrection of hyponatremia can result in irreversible neurologic disability like osmotic demyelination syndrome. Few prospective studies have identified the individuals at high risk of overcorrection under controlled hypertonic saline treatment.  We designed this study to identify the risk factors for overcorrection during hyponatremia treatment. Methods: We performed a post hoc analysis of a multicenter, prospective randomized controlled study – the SALSA (Efficacy and Safety of Rapid Intermittent Correction Compared With Slow Continuous Correction With Hypertonic Saline In Patients With Moderately Severe or Severe Symptomatic Severe Hyponatremia) trial in 178 patients above 18 years old with symptomatic hyponatremia (mean age 73.1 years, mean serum sodium (sNa) concentrations 118.2 mmol/L). Overcorrection was defined as an increase in sNa by >12/18 mmol/L within 24/48 hours at any time. Results: Thirty-seven of 178 patients experienced overcorrection (20.7%). Overcorrection was independently associated with initial sNa level (≤ 110 mmol/L: 7 points; 110-115 mmol/L: 4 points; 115-120 mmol/L: 2 points; 120-125 mmol/L: 0 point). chronic alcoholism (7 points), severe symptoms of hyponatremia (3 points), and initial potassium level (< 3.0 mmol/L: 3 points). The NASK score was derived from these four risk factors for overcorrection (hypoNatremia, Alcoholism, Severe symptoms, and hypoKalemia) and was significantly associated with overcorrection (odds ratio 1.41, 95% CI 1.24 to 1.61; P <.001) with good discrimination (area under the receiver operating characteristic curve 0.76, 95% CI 0.66 to 0.85; P <.001). The AUROC value of the NASK score was statistically better comparing to those of each risk factor. Each risk factor contributed to overcorrection by diuresis. Conclusions: In treating patients with symptomatic hyponatremia, individuals at high risk of overcorrection were predictable using a novel risk score summarizing baseline information.