A wearable automatic injection device is provided for administering a final medicament to a patient. The wearable automatic injection device comprises a housing, an injection assembly for injecting the patient with the final medicament, a container holding a bulk intermediate medicament and a diluent to be mixed to form the medicament, and a mixing mechanism for mixing the bulk intermediate medicament and the diluent in the container to form the final medicament prior. A system for administering a final medicament to a patient is also provided. The system comprises a container, a mixing mechanism for mixing a bulk intermediate medicament and a diluent in the container to form the final medicament, and a wearable automatic injection device configured to receive the container.