The aim of the paper is to present the impact of GDPR regulation on the level of transactional costs in the management of medical data in medical entities. The management of medical data has been presented as a series of activities of transactional nature. Futhermore, the impact of institutional solutions of the GDPR on the specificity of assets, the frequency and uncertainty of transactions included in the management of medical data was considered. As the result of the analysis, the following conclusions were drawn: 1. The new regulations defined in the regulation of the GDPR will significantly increase the transactional costs of adaptation measures. 2. The implemented changes will result in the greater specificity of both the assets and the frequency of transactions. 3. The effect of introducing changes will be a partial reduction of the uncertainty accompanying the transactions. The rights and obligations of the parties in the process of managing medical data will become more transparent.