Therapy for adverse drug reactions (ADRs) often results in the application of blood components. This study aims to assess the demand for blood components and the resulting economic burden (hospital perspective) in German hospitals induced by ADRs leading to admissions to departments of internal medicine. In this prospective study, ADRs leading to hospitalization were surveyed in four regional pharmacovigilance centres in Germany during the years 2000–2007. ADRs assessed as ‘possible’, ‘likely’ or ‘very likely’ were included. Market prices for blood components and hospitalization data were determined by desktop research. A probabilistic sensitivity analysis was performed. A total of 6099 patients were admitted to internal medicine departments because of an outpatient ADR of whom 1165 patients (19.1%; mean age, 73.0 ± 13.0 years) required treatment with blood components owing to major bleeding events. Overall consumption was 4185 erythrocyte concentrates (EC), 426 fresh frozen plasma (FFP) and 48 thrombocyte (TC) units. On the basis of statistical hospital data, we estimated a nationwide demand of approximately 132,020 EC, 13,440 FFP and 1515 TC units, resulting in total costs of €12.66 million per year for all German hospitals. Some 19.2% of all ADR cases were assessed as preventable. Theoretically, a nationwide decreased demand for blood components and a savings potential of €2.43 million per year could be achieved by preventing ADRs in Germany. Blood components are used in one-fifth (mainly gastrointestinal bleeding) of all ADRs, leading to hospitalizations in internal medicine departments. Both blood demand and hospital procurement costs can be significantly lowered by preventing ADRs.