The Impact of Prescription Barriers to Special Low Protein Foods and Protein Substitutes on PKU Care: Findings from a National Survey of Metabolic Dietitians

Background/Objectives: Timely access to protein substitutes and special low-protein foods (SLPFs) is essential for effective dietary management of phenylketonuria (PKU). As key healthcare professionals responsible for coordinating and delivering nutritional therapy, metabolic dietitians are directly involved in managing prescription-related issues that may arise within the access pathway. This study aimed to identify the main prescription-related barriers experienced by metabolic dietitians in the UK and to explore their implications for patient care, clinical workload, and the delivery of specialist PKU services. Methods: A structured questionnaire was distributed by the National Society for Phenylketonuria to dietitians involved in the care for individuals with PKU in the UK. Anonymised responses were analysed descriptively to identify the types, frequency, and impact of prescription-related issues. Results: A total of 448 responses were received from metabolic dietitians across the UK reporting prescription-related problems affecting dietary products. Most reported incidents involved children (306/446; 68.6%). Among responses specifying the affected product category (n = 443), SLPFs accounted for most reported problems (261/443; 58.9%), followed by protein substitutes (120/443; 27.1%) and finally combined protein substitute and SLPF issues (62/443; 14.0%). Qualitative analysis identified barriers across all stages of the prescribing pathway, with issues primarily relating to GP prescribing processes, home delivery and supply, pharmacy services, and broader administrative and system-related factors. These disruptions affected continuity of dietary management and metabolic care, with reported consequences including reduced access to prescribed dietary products, difficulties maintaining dietary adherence, increased patient and family burden, anxiety and frustration, and a substantial hidden workload for metabolic dietetic services. Conclusions: Prescription-related problems represented a significant barrier to timely access to essential medical foods for individuals with PKU in the UK. The findings highlight challenges across the prescribing and supply pathway that compromise access to both protein substitutes and SLPFs, impose additional burdens on patients and families, and increase workload for specialist metabolic dietetic services. Addressing these system-level barriers, alongside strengthening communication, coordination, and prescribing processes across stakeholders, may improve continuity of dietary treatment and enable more efficient delivery of specialist metabolic care.