A handheld diabetes management device having a database management system is disclosed. The device comprises a plurality of input modules, including a blood glucose reader, a user interface, a communications interface, and a continuous blood glucose input module. The input modules output data used to generate data records of different record types. The device further comprises N databases, each database having a different frequency range associated thereto, wherein the new record is stored in a particular database of the N databases based on the frequency range of the particular database and the frequency of the particular record type, and N is an integer greater than 1. The device further includes a database operation module that performs database operations on the N databases. The database management system provides increased reliability in the keeping of records on which medically important decisions are made.