Cartridge replacement guide · October 5, 2026
Changing a cartridge in a reusable peptide pen involves opening the holder, resetting the piston, inserting the replacement and bringing the mechanism back into position. The animated tutorial below shows the sequence using one consistent pen model based on the supplied Elev8 Lab pen photos.
Watch the animated tutorial
The animation covers cartridge replacement and mechanical setup. Follow your model’s separate instructions for needle attachment, its required flow check and any subsequent use.
Know the parts before you start
The outer cap covers the front of the pen. Beneath it, the clear cartridge holder connects to the pen body at the centre joint. The piston rod projects from the front of the body and meets the cartridge’s rubber stopper. The rear control operates the mechanism.
Use a clean workspace and wash and dry your hands. Have the correct replacement cartridge and the pen’s instructions ready. If a needle is attached, remove and dispose of it using the method specified in those instructions before opening the holder. Keep the replacement cartridge’s sealed end intact.
How to replace the cartridge
Remove the cap and open the holder
Take off the outer cap. Hold the pen body steady and gently unscrew the clear cartridge holder at the centre joint. Set the holder aside so that you can see the small piston rod at the front of the body.
Turn the joint gently. If it will not release as expected, check the model’s opening instructions before applying more force.
Reset the piston rod
On the type of pen illustrated, gently push the piston rod fully back into the body with a fingertip. Resetting it gives the replacement cartridge room to seat correctly.
Use this push-back method only if it is specified for your pen. Some mechanisms reset differently. If the rod resists, stop and check the manual rather than forcing it.
Remove the old cartridge and insert the replacement
Slide the old cartridge out of the detached holder. Insert the compatible replacement with its small, sealed end facing the needle end and its rubber stopper facing the pen body.
Keep the cartridge straight as it slides into place. Confirm its orientation before reconnecting the holder; do not try to compensate for an incorrectly seated cartridge by tightening the joint harder.
Reattach the cartridge holder
Line up the holder with the pen body and screw the two sections together gently until the holder is secure. The joint should engage smoothly.
If it feels crooked, binds or will not close normally, stop. Check the cartridge position, piston reset and thread alignment against your model’s instructions.
Bring the piston to the rubber stopper
There may be a gap between the reset piston rod and the cartridge’s rubber stopper. On the illustrated mechanism, gently operating and pressing the rear control advances the rod until it meets the stopper.
Follow your pen’s specified setup sequence, repeating only as directed. This is a model-specific setup step, not a dose setting. Do not copy a dial number or click count from another pen, and do not keep forcing the control once the mechanism meets resistance.
Return the control and check the assembly
Return the rear control to its starting position as directed for your model. Check that the holder is secure, the cartridge is seated correctly and the pen has been reset and assembled as instructed.
The cartridge replacement is now complete. Before any injection, follow the instructions for attaching a new compatible needle and performing the required flow check.
If something does not move smoothly
A holder that will not close, a piston that will not reset or a control that feels unusually stiff is a reason to pause. Recheck the exact model instructions and cartridge compatibility. Avoid forcing the threads, rod or rear control. If the problem continues, contact the pen supplier or manufacturer for that model’s troubleshooting procedure.
Keep cartridge replacement separate from dose calculations
Changing the cartridge does not determine the amount to use. Pen dial markings and click volumes are device-specific. A U-100 syringe conversion does not establish a reusable pen’s delivery volume or the amount of compound delivered.
For preparation and storage context, read the peptide reconstitution and storage guide alongside your product and device instructions.
For the difference between mass and volume, read mg, mcg, mL and syringe units explained. You can also browse the Peptide Workbench guides and references.