Company X develops a laboratory information system (LIS) called System Y. The information system has a two-tier database architecture consisting of a production database and a historical database. A database constitutes the backbone of a IS, which makes the design of the database very important. A poorly designed database can cause major problems within an organization. The two databases in System Y are poorly modeled, particularly the historical database. The cause of the poor modeling was unclear concepts. The unclear concepts have remained in the database and in the company organization and caused a general confusion of concepts. The split database architecture itself has evolved into a bottleneck and is the cause of many problems during the development of System Y. Company X investigates the possibility of integrating the historical database with the production database. The goal of our thesis is to conduct a consequence analysis of such integration and what the effects would be on System Y, and to create a new design for the integrated database. We will also examine and describe the practical effects of confusion of concepts for a database conceptual design. To achieve the goal of the thesis, five different method steps have been performed: a preliminary study of the organization, a change analysis, a consequence analysis and an investigation of the conceptual design of the database. These method steps have helped identify changes necessary for the organization, a new design proposal for an integrated database, the impact of the proposed design and a number of effects of confusion for the database.