OBJECTIVES: To determine the costs and medical resource use for the management of injection-site reactions (ISRs) and flu-like symptoms (FLS) associated with injectable disease-modifying drugs (DMDs) used to treat patients with relapsing–remitting multiple sclerosis (RRMS) in the UK. METHODS: A survey was carried out amongst NHS nurses to understand the management of adverse events occurring with injectable DMD use. Data were collected via a postal questionnaire. Responses were compiled for the frequency and duration of side-effects, support received and medical consultations required for adverse event management. The unit costs were derived from the Personal Social Services Research Unit, the Office for National Statistics and the British National Formulary. Once all parameters and unit prices were characterised with conservative approaches for missing data (e.g. no GP consultation mandatory before antibiotics prescription), computations were processed to determine means and standard deviations (SDs). RESULTS: In total, 19 NHS nurses managing significant numbers of patients with MS for different primary care trusts participated in the costing survey. On average, the nurses reported that patients experienced 27 ISRs per year of those 33% experienced ISRs only at treatment start while 21% experienced ISRs continuously during the year. Seventy-four percent experienced FLS only at treatment start and 11% continuously. The average cost for the management of ISRs per year was £187 (SD £209) equivalent to an average cost of £7 per event. The average cost for the management of FLS per year was £166 (SD £144) equivalent to an average cost of £6 per event. CONCLUSIONS: This is the first UK study to provide data on the costs associated with management of ISRs and FLS occurring with injectable DMDs. These data, alongside prevalence estimates, enabled us to calculate the costs of managing adverse events associated within DMDs in an economic model.