A short-acting estrogen with much lower receptor affinity than estradiol. Licensed in the UK, Europe and Australia as a 0.1% cream or 0.005% gel; not FDA-approved in the United States, where access is through compounding only. It is the majority component of Bi-est.
Also known as E3, Ovestin, Oestriol
Educational research referenceTRT / HRT & Ancillary
Quick reference. Everything you need to run Estriol —
dosing, frequency, reconstitution math for the vial sizes people actually buy,
and what it stacks with. For anything specific to your situation,
ask the Guru.
Estriol quick start
Route
Vaginal or topical
Typical dose
0.5–2 mg
Frequency
Once or twice daily
Half-life
Short — hours.
Cycle
Continuous, or cycle-day anchored where a prescriber sets one.
These are the numbers people actually run, drawn from the published record and from
what the community has settled on over time. Educational reference, not medical
advice — a starting point to work from, and one you can adjust as you learn how you
respond.
How to run it
How often
Once or twice daily
Cycle length
Continuous, or cycle-day anchored where a prescriber sets one.
Half-life
Short — hours.
Route
Vaginal or topical
Consistency matters more than perfect timing. Pick a slot in your day you will
actually keep, and let DoseIQ handle the rest.
For women
Because its systemic effect is weak, estriol is the estrogen usually chosen when the goal is local vaginal tissue rather than vasomotor symptoms. Compounded doses commonly run 0.5–2 mg once or twice daily.
What to expect
Most people tolerate Estriol well. Here is what is worth knowing going in,
so nothing catches you by surprise.
Not FDA-approved in the US; US supply is compounded, which means no approved label and no batch-level regulatory oversight of potency. NASEM’s 2020 report to FDA found the evidence base for compounded hormone preparations rests largely on anecdote and prescriber testimony.
Known interactions
Interactions involving Estriol's drug class that DoseIQ screens for.
Each one cites where it comes from — an FDA label section or the published
record — because an interaction warning you can't trace is just noise.
Worth knowingAromatase inhibitor + estrogen — working against each other
One suppresses estrogen while the other supplies it — pharmacologically contradictory unless very deliberately prescribed.
What to do: Worth confirming both are supposed to be running at once.
Source: Mechanism; anastrozole label
DoseIQ screens your whole protocol against these rules automatically — every
compound, prescription and supplement you track, cross-checked as you add them.
Serious flags are always free.
Preparing it
Estriol does not need reconstituting — it comes ready to use.
Nothing to reconstitute. Dosed by clicks from a dispenser, or as a measured cream weight.
This page is an educational research reference and is not medical advice.
Dose figures reflect the published record and what the community has converged on —
starting points to weigh, not instructions. Consult a qualified healthcare provider
before starting any protocol.