To clarify, I think it's most common for people to open a vial and use it until it's gone. Most people don't throw away their vials after a month, though if there is a reason to suspect contamination you should throw away the vial. My point was just that most doctors will feel comfortable writing a script that lets you buy a new vial once a month under the pretext that vials used longer than that can get contaminated, especially if they are cored. It's a plausible and reasonable excuse to get a Rx that lets you stockpile, even with a doctor that might otherwise not want to enable stockpiling.
As far as how long they last: the vials of estradiol valerate I get are 100 mg in 5 mL of oil, and I currently inject around 9 mg per week (a relatively high, monotherapy dose), so a vial lasts me almost around 11 weeks or 2.5 months. The next vial I open is just whichever one expires the soonest (First In First Out). Since I buy a new vial once a month, this means I keep accruing a back stock while using up my oldest vials. I'm currently using a vial I opened in September but bought in April.
So it's dependent on your dose, whether you accidentally core your vial, and other factors as to how long a vial will last you, but this method should still help you have a regular excess that you can stockpile.
Besides stockpiling, injections are a better way to get the estrogen anyway. If you haven't already, I recommend this guide which covers differences between routes of administration. tl;dr only around 5% of the dose of oral estrogen ends up in your blood stream, most of it is filtered by your liver and it's a very poor way to get estrogen in your body. The effects on the liver in the long term might contribute to blood clotting, strokes, or cardiovascular events. Injections don't have these downsides, most of the dose ends up in your bloodstream and it doesn't tax your liver or contribute to a health risk (besides the typical risks any injection might carry, such as infection at the injection site if you don't follow proper procedures like reusing needles and so on).
For more about injections: https://old.reddit.com/r/TransWiki/wiki/hrt/injections
I recommend subcutaneous (subq) injections with a small gauge needle like 27G because it's relatively painless and fool-proof compared to intramuscular (IM) injections. You will essentially need these things:
- 0.5 mL syringes (look for ones without needles and the twisting Leur-lock connection type)
- 27G needles for injecting
- 21G needles for drawing the oil from the vial into the syringe
- alcohol swabs for sterilizing the vial, and for swabbing your injection site
- bandaids for after injecting
As I mentioned before, drawing with a 21G needle instead of 18G to reduce chance of coring your vial.
Here is a video showing how to do an injection: https://www.youtube.com/watch?v=7TP0rTlQVao
Here is a PDF guide for injections, including diagrams showing appropriate injection sites for subq: https://fenwayhealth.org/wp-content/uploads/MG-6_TransHealth_InjectionGuide.pdf
Here is a video showing proper technique to avoid coring a vial: https://www.youtube.com/watch?v=w5F0SLoMjC8
yes, there are lots of ways to optimize.
23G sounds good for drawing, and I think that is the more standard recommendation (looks like the /r/TransWiki guide lists 23G and 25G), though I haven't used it personally.
Re-using the same needle you drew with to inject with can make the needle a bit more dull and I have found it makes the injection more likely to hurt (apparently I'm not the only one). It is also standard practice to change the needle between drawing and injecting to further reduce chance of infection. I've read that plenty of people don't change needles between drawing and injecting, but I'm not sure I would necessarily advertise this as a good practice, esp. for beginners.
Part of the reason I suggested subq is because it allows for injecting with a smaller gauge needle like 27G, which is less painful and more accessible to people like me who suffer from needle phobia. That's part of why I think of it as more foolproof, but also because subq doesn't require targeting a specific muscle or injecting to the correct depth like IM does.
I'm not sure about irritation from subq that IM doesn't cause, so I would love more detail on that. I just would imagine the smaller needle, the shorter length, etc. makes it less irritating than a larger gauge and longer needle.
You can also buy low deadspace syringes without using a fixed needle, but I find these kinds of optimization less relevant when regularly accruing excess medication and there is incentive to use up old medication before it expires. A vial is like $11 for me, so it is also rather cheap, and the medication waste in that context is not worth overly concerning yourself over.
It would make more sense for DIY, though, when the medication is more expensive (and supply might be less reliable and more scarce). I have never looked at the extra cost of low deadspace syringes compared to the cost of wasted medication from that deadspace, but even with normal syringes I know people have used bubbles in their doses to leave air in the deadspace and get all the medication (correct dosing becomes a bit tricky in this situation, just have to be mindful that you are measuring your dose accurately).