A medical instrument/analyzer for measuring a biological sample using a test strip. The instrument comprises: a housing with an exterior surface, an internal surface, and an interior volume; an analytical unit within the interior volume with a test strip mount; a test strip port between the exterior and the interior surfaces; a shutter configured for sealing the test strip port when closed, wherein the shutter comprises a test strip support aligned with the test strip port and mount when the shutter is in the open position, wherein the shutter has a first sealing surface, the test strip port has a second sealing surface, and the first sealing and second sealing surfaces are configured to mate in the closed position, wherein the shutter comprises a mechanism for moving between the open and the closed position; and an actuator configured for moving the shutter between the open and closed position.