Mixing pen needle

1. A method of mixing a medicament and delivering the medicament from a medication pen comprising:

selecting a first dose of a first medicament contained in a first medication compartment and selecting a second dose of a second medicament contained in a second medication compartment;

activating a first dosing mechanism by moving a first dosage plunger engaged in the first medication compartment delivering the first dose into a pen needle assembly received on the distal end of a movable housing, said pen needle assembly comprising a patient end needle, a filler needle, and an intermediate collapsible mixing reservoir;

wherein the collapsible mixing reservoir receives the first dose through the filler needle;

disengaging the first medication compartment from the collapsible mixing reservoir;

moving the movable housing and engaging the second medication compartment with the collapsible mixing reservoir;

activating a second dosing mechanism by moving a second dosage plunger engaged in the second medication compartment delivering the second dose into the collapsible mixing reservoir through the filler needle;

collapsing the mixing reservoir thereby forcing the first and second doses in the mixing reservoir through the patient end needle.

2. The method of claim 1 , wherein the first and second medication compartments are positioned in a pen body connected to the movable housing by a shaft; and

the collapsible mixing reservoir is disengaged from the first medication compartment by moving the movable housing and the shaft in a distal direction away from the first dosage plunger; wherein the movable housing and the shaft are rotated to align the collapsible mixing reservoir with the second medication compartment; and

wherein the collapsible mixing reservoir is engaged with the second medication compartment by moving the movable housing and the shaft in a proximal direction toward the second dosage plunger.

3. The method of claim 2 , wherein the pen needle assembly is threaded on an internally or externally threaded opening on the distal end of the movable housing.

4. The method of claim 1 , including the steps of rotating a first dosage knob protruding from the proximal end of the medication pen to set the first dosage prior to activating the first dosing mechanism; and rotating a second dosage knob protruding from the proximal end of the medication pen to set the second dose prior to activating the second dosing mechanism.

5. The method of claim 1 , wherein the collapsible mixing reservoir includes a stopper moving within and sealing the mixing reservoir, and wherein a sleeve on the exterior of the pen needle assembly is secured to the stopper, so that moving the sleeve in a proximal direction moves the stopper to collapse the mixing reservoir, forcing medication out of the patient end needle.

6. The method of claim 1 , wherein the first medicament is insulin and the second medicament is glucagon-like peptide.