We've all had it drilled into us: get your estradiol into the 100–200 pg/mL window and you're "optimal." I've quoted that range myself. So I went looking for where it actually comes from... and a new systematic review basically pulled the rug out.

The authors went through 49 studies looking for evidence that the 100–200 pg/mL range produces better feminization or fewer adverse events. They didn't find it. Nothing showed that landing in that specific window gets you better outcomes than sitting outside it.

In plain terms, that range is a **monitoring convenience,** a sensible place to keep an eye on safety and consistency but it is not a feminization dial you have to hit exactly. Your breast growth, fat redistribution, skin, all of it, is driven by far more than whether your number reads 150 vs. 190 on the one morning you happened to get drawn (and that number swings a LOT with timing, route, and lab).

So if you are spiraling because you came back at 90, or 240... breathe. The number is a tool, not the goal. :)

This is NOT "targets are useless" or "dose however you want." It's "we don't have good evidence for *this specific range*." The underlying data is mostly observational and too varied to pool, so the real headline is how thin the evidence base actually is, which is its own argument for working *with* a provider rather than chasing a number alone.

Study linked below. What have your providers told you about targets — did anyone ever frame it as monitoring vs. an outcome?



The 100–200 pg/mL estradiol "target" isn't actually evidence-based (new 2025 systematic review)