The Nutrition Management Guideline for individuals with urea cycle disorders (UCDs) is part of a larger project undertaken by the Emory University's Medical Nutrition Therapy for Prevention (MNT4P) program and Genetic Metabolic Dietitians International (GMDI) to develop nutrition management guidelines for inherited metabolic disorders (IMD).

The purpose of this guideline is to foster optimum nutrition management of individuals with UCDs and reduce the uncertainty and variability in the management of these IMDs.

The most recent international guideline for UCDs was the 2019 revision of the original 2012 European recommendations, which provided guidance for the diagnosis and overall management of UCDs. This 2026 guideline advances the field by providing the first nutrition-focused UCD guideline developed through a rigorous evidence- and consensus-based Delphi-Nominal-Delphi-Field Testing (DNDF) methodology. It integrates recent evidence, contemporary clinical practice, and expert consensus across acute management, chronic care, monitoring, education and support, reproductive health, transplantation, and conditions with overlapping phenotypes. 

The target population includes individuals with UCDs at all life stages from the newborn period, through childhood, adolescence, the adult years, and during pregnancy. These guidelines include management during periods of health and illness.

This guideline focuses on UCDs involving deficiencies of the primary urea cycle enzymes and related transporters directly responsible for ureagenesis, specifically carbamoyl phosphate synthetase 1 deficiency (CPS), ornithine transcarbamylase deficiency (OTC), argininosuccinate synthetase deficiency (CIT-I), argininosuccinate lyase deficiency (ASA), and arginase 1 deficiency (ARG). 

Conditions associated with secondary urea cycle dysfunction or overlapping hyperammonemia phenotypes, such as N-acetylglutamate synthase deficiency (NAGS), carbonic anhydrase VA deficiency (CA-VA), hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome, lysinuric protein intolerance (LPI), and ornithine aminotransferase deficiency (OAT), are addressed separately where relevant. These conditions were not the primary focus of the guideline. For several of these conditions, the published nutrition evidence-base was limited; therefore, recommendations were informed more heavily by expert consensus, as described in the Methods. 

The guidelines are intended for use by metabolic dietitians, physicians, other members of the health care team, and researchers who collaborate to provide care and advice for individuals with UCDs as well as their families, advocates, and others.

Sponsorship is shared by MNT4P and GMDI.

Funding for this project has been provided by MNT4P and GMDI.

Contents of the guideline include:

• Methodology used for development of evidence- and consensus-based guidelines
• Background information about UCDs, their diagnosis, biochemical pathway, and nutrition treatment rationale
• Nutrition care in UCDs, including assessment, nutrition problem identification, nutrition intervention with evidence- and consensus-based recommendations, and monitoring and evaluation
• Specific recommendations with ratings based on the strength of the evidence
• Consideration for implementation
• Directions for future research