

please do not use 18g needles for drawing, you will destroy your vial. additionally while you can switch the needle theres really no need to (see insulin needles, they are fixed), but also no reason not to. 25g basically guarantees coring is not a problem.
they recommend 18g in regular healthcare stuff because its standard practice and you arent expected to be using a vial more than a few times, diy vials last significantly longer than prescription ones (though prescription ones also last a very long time and the “use by” date or whatever they have on them is bullshit 99% of the time)
given you were drunk making sure you actually ordered it from a reputable source is probably a good idea
there a list of them over on https://hrtcafe.net/Estrogen/estradiol_injections.html