A method of preparing a double chamber container (1) comprises the steps of: filling a substance in the interior of the double chamber container (1), freeze-drying the substance inside the double chamber container (1), inserting a middle plunger (81) in the interior of the double chamber container (1) such that a distal chamber and a proximal chamber are formed, wherein the middle plunger (81) seals the distal chamber from the proximal chamber and wherein the freeze-dried substance is inside the distal chamber, filling a reconstitution medium in the proximal chamber of the double chamber container (1), and sealing a distal opening (14) of the double chamber container (1) and a proximal opening (13) of the double chamber container (1). The method particularly also comprises the steps of providing a holder (2) having a seat (21) designed to receive the double chamber container (1) in an upright position and arranging the double chamber container (1) in the seat (21) of the holder (2) such that, in the upright position, a distal end side (12) of the double chamber container (1) extends downwardly and a proximal end side (13) of the double chamber container (1) extends upwardly. Thereby, the double chamber container (1) is arranged in the seat (21) of the holder (2) while the substance is filled in the interior of the double chamber container (1), while the substance is freeze-dried inside the double chamber container (1), while the middle plunger (81) is inserted in the interior of the double chamber container (1), while the reconstitution medium is filled in the proximal chamber of the double chamber container (1), and while the proximal opening (13) of the double chamber container (1) is sealed.
