Body fluid testing device for analyzing a body fluid comprises a test media tape adapted to collect the body fluid. The test media tape comprises a tape and test media portions. A free tape portion without test medium is located between successive test media portions. The testing device further comprises a supply portion. The supply portion comprises a housing in which uncontaminated test media tape is contained. The housing further has an opening for withdrawing test media tape from the housing. The testing device further has a sealing means for closing the opening against the surrounding. A free tape portion of the test media tape is located between a wall of the housing and the sealing means when the sealing means closes the opening. Further aspects concern a test media cassette with sealing means and a method for providing test media while holding them sealed against humidity during onboard storage.