mrmors said:
Thanks for every response, everyone, I appreciate it. I figured it was probably possible, though resetting the plunger could interfere with the settings for each cartridge. I guess I'll check with her whether she's willing to spring for 3 pens!!
@on2jinm this one is strange: for weeks she had no problems with the usual 31g 8mm syringes, rotating injection spots and drawing from the same vial, then out of nowhere she reports pain even though nothing has changed. I tried changing the syringes, changing the peptides, and so on, but it still hurts. Nothing she uses has caused me any reaction either, since I tested it on myself as a guinea pig for her. From what I remember, she previously used those 32g micro needles, I believe 4mm, and stayed on them for months without any trouble, so I was simply wondering whether it makes sense in practice for her to use 3 peptides with a pen.