The 2012 Junior Management of Really Sick Patients with Anorexia Nervosa (MaRSiPAN) guidelines recommends daily blood testing during the initial 5 days of children admitted for inpatient re-feeding. The aim of this study was to determine the clinical utility of this and whether blood tests could be minimised. Single centre retrospective study of children admitted for inpatient treatment of anorexia nervosa (January 2018 - August 2020) was done in a general paediatric ward. Weight, body mass index and re-feeding blood biochemistry were recorded. There were 37 patients, all females, aged between 11-17 years. Weight ranged from 21.4-61.75 Kg. Phosphate levels were 0.6-1.6 mmol/L; mean value 1.22 mmol/L. Over the 5 days of daily testing, mean and median values of all blood results remained within reference ranges. No biochemical indication of re-feeding syndrome was evident and resulted in no change of management. There is limited utility in daily blood testing for patients for the initial 5 days.