Parenteral dextrose during refeeding is associated with electrolyte deficiencies in anorexia nervosa: a route-specific analysis of oral and parenteral nutrition

Abstract Background Although oral feeding is generally preferred over parenteral nutrition during refeeding in patients with anorexia nervosa, parenteral nutrition often plays a critical role in ensuring adequate nutritional support during early refeeding and preventing underfeeding syndrome. However, few studies have examined route-specific effects on refeeding-related electrolyte deficiencies while accounting for the actual caloric intake delivered via each route. Methods We retrospectively examined 208 admissions from 98 patients with anorexia nervosa who were hospitalized in the psychiatric ward of Ashikaga Red Cross Hospital between January 2000 and June 2025. The mean age was 35.3 ± 11.1 years, and the mean body mass index (BMI) at admission was 12.2 ± 2.2 kg/m². In 139 of the 208 admissions (66.8%), nutrition was administered via both oral and parenteral routes. Outcome variables included serum electrolyte levels (phosphorus, potassium, magnesium, and calcium) at admission, at the in-hospital nadir, and the percent decrease from admission to nadir. Explanatory variables included caloric intake via the oral route (with a regular diet and enteral formulas analyzed separately) and the parenteral route (with dextrose and non-dextrose nutrients amino acids and lipids analyzed separately), electrolyte provision per calorie, BMI, and admission laboratory data. Multivariable mixed-effects regression analyses were performed. Results Caloric intake from a regular diet, enteral formulas, and parenteral non-dextrose administration was not associated with nadir electrolyte levels or with percent decreases from admission. In contrast, higher parenteral dextrose caloric intake was significantly associated with lower nadir magnesium levels ( p < 0.001) and with greater percent decreases in magnesium and calcium ( p < 0.001, < 0.05, respectively). Importantly, electrolyte provision per calorie via the parenteral route was not lower than that via the oral route after accounting for reported gastrointestinal absorption rates and carbohydrate proportions in each route. Discussion These findings indicate that higher parenteral dextrose administration during refeeding is associated with electrolyte decreases. This likely reflects route-specific differences in glucose handling: parenteral nutrition delivers glucose directly and rapidly into the systemic circulation, bypassing hepatic first-pass uptake that normally buffers systemic glucose and insulin exposure during oral intake. Our findings underscore the need for heightened vigilance for electrolyte deficiencies, particularly when administering parenteral dextrose.