How to Use a Peptide Pen
A pre-filled pen removes reconstitution and the concentration calculation, which are the two biggest sources of error with lyophilised material. What it introduces instead is a mechanism you need to read correctly. This covers that.
What is in the box
A pen contains a sealed cartridge of made-up solution, a dose dial, a plunger mechanism and a threaded needle mount. Needles are supplied separately and are single use. There is no diluent, because there is nothing to reconstitute.
The label carries the two figures that matter: total peptide content, and concentration. Read both. A 20mg pen and a 40mg pen of the same compound can be physically identical and dial identically while delivering twice the material per unit.
Dial units are volume, not mass
This is the single most important thing to understand, and it mirrors the syringe-unit confusion that catches people out with vials.
On every SerenQ pen, one dial unit is 0.01ml of solution. A 200-unit pen holds 2ml. A 300-unit pen holds 3ml.
How much peptide sits in one unit depends on the concentration of that specific pen. The dial counts liquid; the label tells you what is in the liquid.
Worked through: a 20mg pen holding 3ml is 6.67mg/ml. One dial unit is 0.01ml, so one unit carries 66.7mcg. Ten units carries 667mcg. Full method in dial units explained.
Using it
- Take the pen out of the fridge and let it come toward room temperature. Cold solution is more viscous and harder to deliver evenly.
- Inspect the cartridge. The solution should be clear and colourless. The one exception is GHK-Cu, which is legitimately blue.
- Swab the rubber septum at the pen tip and let it dry.
- Fit a fresh needle. Every time. A reused needle blunts, delivers unevenly and carries contamination back into the septum.
- Prime according to the supplied instructions. Priming clears air from the needle and confirms flow. Skipping it means the first portion of your dial is air.
- Dial the units required and check the number in the window before proceeding.
- Deliver slowly and hold before withdrawing, so the full volume leaves the cartridge rather than tracking back.
- Remove and dispose of the needle in a sharps container. Do not store the pen with a needle attached.
Why the needle comes off
Leaving a needle fitted between uses is the most common pen-handling error. Two things go wrong. Air is drawn back into the cartridge as the contents cool and contract, which fouls the next prime. And the sealed system stops being sealed, which is the pen's main advantage over a multi-dose vial in the first place.
Storage
Refrigerate at 2 to 8 °C, upright, away from light. A pen holds made-up solution rather than dry powder, so the stability rules for a reconstituted vial apply from the moment it is manufactured.
Brief periods at room temperature in transit are normal. Prolonged warmth is not. More in storage and stability.
When something looks wrong
- Cloudy or particulate solution — do not use.
- Dial will not turn — usually the cartridge is at its end, or the mechanism has been forced past its limit.
- Nothing delivers on priming — needle not seated, or blocked. Change it.
- Solution leaks at the tip — needle not fully threaded, or the septum has been punctured off-centre.
- The pen has frozen — discard it, regardless of appearance.
Frequently asked
Do I need bacteriostatic water? No. There is nothing to reconstitute, and the sealed cartridge does not need a preservative for repeat withdrawals the way a punctured vial does.
Can I refill a pen? No. The cartridge is sealed at manufacture and is not designed to be opened or refilled.
How many doses does a pen hold? Total units divided by units per dose. A 300-unit pen dialled at 10 units gives 30 doses.
Is a pen more accurate than a syringe? More repeatable. A dial increment is a fixed mechanical property, where reading a syringe barrel varies between people and occasions.