Disclosed is an auto injector and a method for administering a medicament. The auto injector comprising: a housing; a cartridge receiver; a drive module coupled to move a plunger rod configured to move a first stopper; a temperature sensor configured to provide a temperature signal indicative of the temperature of the medicament in the cartridge; a processing unit configured to: receive the temperature signal; control the drive module to move the plunger rod from a first plunger rod position to a mix plunger rod position wherein the movement from the first plunger rod position to the mix plunger rod position is based on the temperature signal.