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Making injections as smooth as possible

How an insulin pen made my subcutaneous estrogen injections so much easier

A huge thanks to a twitter user who has since deactivated for bringing this to my attention, I wish I could give proper credit but the original post is gone.

Why an insulin pen?

Insulin pens are a great delivery mechanism allowing you to precisely dial your dose in steps of 0.01ml, insert the needle in the injection site, push a button and voilà! the drug is precisely delivered.

But how do we utilise this efficient delivery mechanism for something besides insulin, like HRT? Below I will outline how I personally set out to accomplish this. But first…

Disclaimers & Caveats

I am not a medical professional, I am not advising you to do anything, I am just a trans woman documenting my experience with injecting.

Some important things to note:

The equipment

Insulin Pen

There are a few options when it comes to choosing a pen, the important thing is that they take standard 3ml cartridges.

The other important thing to consider is the dosing precision, insulin pens give a number in units, these units are typically based on U-100 insulin, in which 1 unit equates to 0.01ml. Pens are typically available in 1 or 2 unit steps. So I choose ones that have 1 unit steps for the increased granularity.

Two I’ve used that meet this criteria are the HumaPen Savvio, and the Autopen Classic (my preferred choice for its low force to inject)


For the pen needles I use 29G, which is the largest available to me for pens, I use the 10mm length ones as these are the shortest length available to me at 29G.


This is the only part not obtained from a reliable source, as such the sterility and quality of this is not going to be guaranteed. I source mine from AliExpress, searching for “3ml insulin bottle” and autoclave them myself. Sterility is very important.

On a totally unrelated note… a sponsored message #ad

Beawitching Communities sell glass vials that have been autoclaved for making art out of, to clarify this has nothing to do with the contents of the article and is just an advertisement on how you can support us :)

Graphic with a glass vial pictured and the text: Support us, 3ml glass vials for miniature crafts

ok #ad over…

How I prepare

I use a syringe with my orange 25G needles as the draw up needles I have are too large and often end up coring the small cartridges. Ensuring there are no air bubbles I transfer the contents from my vial into the cartridge, repeating until full, being careful not to overfill and risk the bottom popping out and losing 3ml of precious estrogen.

I place the full cartridge in the pen, attach a needle, and turn the dial by 2 units at a time until the fluid flows out the end.

At this point the pen is prepared for injection, I followed this video guidance on administering an injection using a pen to familiarise myself with the process.

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