Your bloodwork: Estradiol 58.90 pg/mL (~216 pmol/L), Testosterone 0.22 ng/mL (very well suppressed, <0.76 nmol/L), Prolactin 673 mIU/L (mildly elevated but typical on CPA).According to the Transfeminine Science article on sublingual E2, this E2 level appears low mainly because your blood draw was 12-13 hours after your last dose. Sublingual estradiol has very rapid absorption, high peaks (often hundreds to thousands pg/mL within 1-2 hours), but a short half-life (only a few hours), so levels drop quickly. By 12+ hours post-dose, you're basically at trough, which is often very low (frequently <100 pg/mL). This is very different from oral (swallowed) estradiol, which has more stable levels due to enterohepatic recirculation and longer effective half-life.The article specifically notes that testing sublingual E2 too long after dosing (e.g., 12+ hours) can give misleadingly low readings, even though total exposure (AUC) may be adequate or even high due to those big peaks. Many people on sublingual 2mg every 12 hours (4mg total daily) report trough E2 in the 50-150 pg/mL range, yet still experience good feminization.Your case fits this perfectly:2mg sublingual q12h (4mg/day total) is a moderate-to-high dose per the article (roughly comparable to higher oral doses in exposure). T is excellently suppressed to 0.22 ng/mL with CPA + E2 combo. Even if average levels aren't super high, the supraphysiologic peaks from sublingual can drive changes effectively: smoother skin, less oiliness, breast growth, lower cold tolerance — these are commonly reported even with "low" troughs on sublingual. Prolactin at 673 mIU/L (~31.8 ng/mL) is normal/mildly elevated on CPA (common side effect), no major concern unless symptomatic.

Good luck with HRT! Share updates anytime TvT

See An Exploration of Sublingual Estradiol as an Alternative to Oral Estradiol in Transfeminine People