Abstract In the UK, for patients with inherited metabolic disorders (IMD) the traditional system for acquiring essential dietary products [patient prompted prescriptions generated by a medical general practitioner (GP) and dispensed by a chemist] is problematic. Objective To investigate the efficacy of a home delivery service (HDS) for essential dietary products (EDP) (i.e. protein substitutes, milk replacements, energy and vitamin and mineral supplements) for subjects with IMD, particularly examining any prescription and dispensing errors, metabolic control and consumer satisfaction. Methods A prospective, controlled, home delivery trial for EDP was conducted in patients with IMD for 12 months. Sixty-two patients with IMD [50 with phenylketonuria (PKU); 12 with other IMD: aged 6 months–30 years] were recruited. Thirty subjects used a monthly HDS (Homeward: Nutricia) to receive EDP, 32 remained on the traditional system. Each month, the HDS checked home stock levels of EDP, obtained their prescriptions directly from GP's, and then delivered them to the subjects’ homes. An independent researcher completed monthly telephone interviews with patients/parents about any EDP prescription errors or delay in receipt. Results Incorrect protein substitute was dispensed once by the HDS compared with nine subjects who had 12 errors in the control group (P = 0.01); incorrect flavours of protein substitute were dispensed to the home delivery group once compared with eight subjects getting 11 errors via the chemist (P = 0.03). The HDS delayed delivery of protein substitute for one subject on three occasions compared with 39 occasions in 16 subjects via the chemist (P = 0.001). In patients with PKU, plasma phenylalanine control deteriorated in the control group (P < 0.05) but not in the HDS group. Conclusions The long-term use of a HDS for EDP in IMD is safer, effective and more reliable than conventional systems.