What did @carla.cassandra actually say?
Carla documented her first estradiol injection after spending roughly three to four months on oral estradiol pills. She described switching because commenters told her "injections was where it's at" and her follow-up bloodwork suggested the pills weren't delivering results to the degree she wanted. Midway through the injection, she paused and asked out loud: "this says for intramuscular use only, I'm doing subcutaneous, is that fine?" She then proceeded anyway, choosing her abdomen as the injection site based on prior patch experience. She was transparent that she is "clearly not a nurse or a medical professional."
Credit where it's due: she did wait three months before reassessing, checked in with her doctor, and was upfront about her anxiety and inexperience. That's more self-awareness than a lot of injection tutorial content shows. The problem is what happened after the check-in.
Does the science back up the switch from pills to injections?
Yes, broadly. Oral estradiol produces lower and more variable serum estradiol levels compared to injectable estradiol valerate or cypionate, and first-pass liver metabolism is a real pharmacokinetic issue. The switch to injections is clinically defensible, but the route-of-administration confusion she had mid-injection is not a minor detail.
Injectable estradiol formulations in the U.S., including estradiol cypionate and estradiol valerate, are labeled for intramuscular (IM) use. Subcutaneous (SubQ) estradiol injection is practiced in some gender-affirming care settings, but the evidence base is thinner. A 2019 study by Doll et al. in Transgender Health found that SubQ estradiol cypionate did produce adequate serum levels in a small cohort, but noted that oil-based injectable formulations are not formally approved for SubQ delivery, and injection site reactions including nodule formation are more common with SubQ oil injections. The Endocrine Society's 2017 clinical practice guidelines (Hembree et al., Journal of Clinical Endocrinology and Metabolism) list IM as the standard route for injectable estradiol in feminizing hormone therapy. SubQ is an off-label adaptation that some clinicians use, but it requires guidance, not a game-time decision mid-injection.
What did she get wrong, and what did she get right?
The most significant problem is the moment she read "intramuscular use only" on the vial and then decided subcutaneous into her abdomen was probably fine. That is not a minor improvisational call. IM and SubQ routes differ in absorption rate, depot formation, and complication profile. Oil-based injectable estradiol deposited subcutaneously carries a documented risk of nodule formation, localized inflammation, and uneven absorption. Asking "is that fine?" to a camera and then proceeding is not informed decision-making.
What she got right: the three-month pill trial before reassessing is consistent with clinical timelines. The Endocrine Society guidelines recommend evaluating hormone levels at three-month intervals early in therapy. Her doctor involvement appears genuine. Oral estradiol's bioavailability limitations are real, and her instinct that pills weren't working as well as injections might isn't wrong on its face. She also did not claim a specific dose was correct for anyone else, which matters.
- Wrong: deciding SubQ abdomen was acceptable after reading an IM-only label, without calling her provider.
- Right: three-month reassessment timeline with physician oversight.
- Right: not prescribing doses or telling viewers to do the same thing she did.
What should you actually know?
Injectable estradiol formulations available in the U.S. are labeled for intramuscular use. If your provider wants you to do SubQ injections, that is a legitimate off-label clinical decision, but it should be an explicit instruction from them, not a mid-injection improvisation. The injection site matters too. Common IM sites for estradiol include the gluteus medius (ventrogluteal) or vastus lateralis. The abdomen is a standard SubQ site, but again, that only applies if your provider has specifically told you to go SubQ with your particular formulation.
If you are on a feminizing HRT protocol and your oral estradiol levels are underwhelming at three months, that is worth discussing with your provider. Factors include dose, whether you are taking pills sublingually versus swallowing them (sublingual dramatically changes absorption), and whether injectable forms are appropriate for your situation. A 2021 review by Pang et al. in Andrology noted that sublingual estradiol achieves peak serum levels comparable to lower-dose injections in many patients, suggesting that not everyone who does poorly on swallowed pills needs to jump straight to injections.
Bottom line: document your injection technique with your provider before your first shot, not after. And if you read "intramuscular use only" on the label during your first solo injection, stop and call the prescribing office.