How to Fill and Use a 3ml Refillable Peptide Pen Cartridge — Research Equipment Guide
The 3ml sterile glass cartridge is the refillable core of a reusable, refillable peptide pen — it holds your reconstituted solution and slots into the pen body for dispensing. Fill a cartridge, load it, and your reusable pen is refilled and ready. This guide covers filling, loading, and storing the 3ml Sterile Glass Cartridge. Written for laboratory and research purposes only.
Looking for how to use the pen itself? This page covers filling and loading the cartridge. For setting up, priming, dialling and pressing the plunger on any V2, V3 or V4 reusable (refillable) pen, see How to Use Your Peptide Pen (with video).
Read the video transcript
Here’s how to fill a cartridge for your Optimised Lifestyle pen. First, wash your hands. You’ll need a sterile three millilitre cartridge, a sterile syringe, your reconstituted solution, and alcohol wipes. Take the cartridge out of its packaging. First, wipe the top of the cartridge with an alcohol wipe, and let it dry. Now draw your solution up into the syringe, up to three millilitres. Here’s a tip: draw a little air out of the cartridge first. That creates a slight vacuum, so it fills fully without compressing the air. Then push the needle through the seal, and dispense slowly. Going too fast adds air and foam. Hold the cartridge upright and check for air. A tiny bubble is normal, and it clears when you prime. Then load it into your pen. Use one cartridge per fill, label each one, and store it as your solution’s guidance says. Always follow the guidance of your healthcare professional.
What Is a 3ml Sterile Glass Cartridge?
The cartridge is a small sterile glass reservoir that holds up to 3ml of reconstituted solution and slots directly into a reusable, refillable peptide pen. Once loaded, the pen’s dial mechanism dispenses from it — see our full pen setup guide for how the dial works (each line equals 1 IU, up to 60 IU per fill). Cartridges are supplied sterile and empty — you fill them yourself once your peptide is reconstituted.
What You’ll Need
- One or more 3ml sterile glass cartridges
- Reconstituted peptide solution — see our reconstitution guide
- Bacteriostatic water for reconstitution — from a laboratory supplier
- A sterile syringe for transferring solution
- Alcohol wipes
- Clean hands, and a fresh cartridge still in its packaging
- A pen body, or the full Peptide Pen Kit if starting from scratch
Filling the Cartridge
1. Wash Your Hands and Unpack the Cartridge
Wash your hands before you start. Then take the 3ml cartridge out of its packaging, keeping the rubber septum clean and untouched.
2. Clean the Septum
Wipe the cartridge’s rubber septum with an alcohol wipe and allow it to dry before drawing any solution.
3. Draw the Solution
Using a sterile syringe, draw the required volume of reconstituted solution — up to the cartridge’s 3ml capacity.
4. Transfer Into the Cartridge
Insert the syringe needle through the cartridge septum and slowly dispense the solution in. Avoid injecting too quickly, which can introduce excess air and foam.
Tip: you may want to draw a little air out of the cartridge first. That creates a slight vacuum, so the cartridge fills fully without compressing the air already inside it.
5. Check for Air Bubbles
Hold the cartridge upright and check for trapped air. Small amounts are normal and are cleared during pen priming — see the priming step in our pen guide.
Loading Into the Pen
Unscrew the pen body and insert the filled cartridge, then attach a pen tip and prime as normal. Full step-by-step instructions are in our How to Use Your Peptide Pen guide.
Cleaning & Storage
A cartridge is intended for a single fill — store the loaded cartridge according to your solution’s own storage guidance (see our peptide storage guide), typically refrigerated at 2–8°C. Wipe the outside of the cartridge with an alcohol wipe if handling it outside the pen. Don’t top up a partially used cartridge with a different reconstitution batch — label and track each fill separately.
Common Mistakes
- Injecting solvent into the cartridge too quickly — dispense slowly, avoiding excess air and foaming.
- Reusing a cartridge across multiple reconstitution batches — label and use one cartridge per fill to avoid mixing concentrations.
- Storing a loaded cartridge outside the pen at room temperature — follow the same storage rules as your reconstituted solution.
- Overfilling past the 3ml mark — can make priming and dispensing inconsistent.
Frequently Asked Questions
Is a peptide pen reusable or refillable?
Both. The pen body is reusable, and you refill it by loading a fresh, filled 3ml cartridge. Pen tips are single use.
Can a peptide pen cartridge be refilled?
Each cartridge is designed for a single fill of reconstituted solution. Once empty, load a fresh cartridge into your refillable pen rather than topping up the same one with a new batch.
Why draw a little air out of the cartridge before filling it?
Drawing a little air out first creates a slight vacuum, so the solution goes in easily and the cartridge fills fully without compressing the air already inside. Then dispense the solution slowly, because going too fast adds air and foam.
How much solution does a 3ml cartridge hold?
Up to 3ml of reconstituted solution, matching the pen’s dial capacity of 60 IU per fill (1 IU per dial line).
Do I need a specific syringe to fill a cartridge?
Any sterile syringe suitable for drawing your reconstituted solution will work — the same syringe used during reconstitution is fine for transferring solution into the cartridge.
How long can a filled cartridge be stored before use?
Follow the storage stability of your specific reconstituted solution — see our reconstitution guide for general storage timelines. Most reconstituted solutions are kept refrigerated and used within a defined window.
Research Use Only Disclaimer: This guide and the equipment referenced are intended for laboratory research purposes only and are not approved for human consumption or medical use.