Objectives There are an estimated 620 000 patients with inflammatory bowel disease (IBD) in the UK. The rising incidence of IBD combined with its incurability has significant cost implications. The aim of this cost of care model was to calculate the annual cost per adult patient of treating ulcerative colitis (UC) and Crohn's disease (CD) from a NHS perspective, and to enable areas of potential cost savings to be explored.

Design The cost of IBD was calculated by summing the costs of treatment, treatment side effects and disease-related complications, accounting for the proportions of patients incurring these costs. Default input values for costs, the percentage of patients receiving each treatment, and the percentage of patients experiencing treatment-related side effects or disease-related complications were determined from national sources and published literature. However, the model permitted the user to input local or alternative data.

Setting The model was designed to be used by NHS trusts in the UK.

Results Using default input values, the annual cost of treating any patient with UC was estimated to be £3084. For a patient with UC in remission, in relapse with mild-to-moderate UC or in relapse with severe UC, annual cost per patient was estimated to be £1693, £2903 and £10 760, respectively. The annual cost for any patient with CD was estimated to be £6156 (£1800 for patients in remission; £10 513 for patients in relapse).

Conclusions While IBD remains a costly condition with modest potential cost savings, this model facilitates calculation of annual costs per patient with UC and CD, and its customisability will help hospitals identify areas where savings could be made.