Estrogen
Estrogen does most of the work in feminizing hormone therapy. It's what grows breast tissue, softens skin, moves fat and, at high enough levels, holds testosterone down. Almost every prescriber now uses estradiol, the same estrogen the ovaries make, and the main decision is the form you take it in.
Going through hormone histories with women before surgery in Bangkok, the question I hear most is why a friend is on patches when she's on pills. There's usually a reason, and it's usually one of the ones below. Doses aren't covered here: they depend on your age, health, other medicines and blood results, and they belong with your prescriber.
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Estradiol, the estrogen prescribers use today
Estradiol is chemically the same as the hormone your body would make if it had ovaries, which is why it's often called bioidentical. It's cheap, off patent, and available in more forms than any other estrogen.
Two older options still turn up. Ethinylestradiol is the synthetic estrogen in most combined contraceptive pills, and it was once used for trans women too. It's far more potent on the liver, which makes clotting proteins, and it's linked to a markedly higher risk of blood clots. It also can't be measured on a standard estradiol blood test. Conjugated equine estrogens (Premarin) have similar problems. Current guidance, including WPATH's Standards of Care and the Endocrine Society's guideline, steers prescribers away from both and towards estradiol.
If you're on a contraceptive pill or an old prescription, whether from years ago or from a source that wasn't a clinic, it's worth taking to a prescriber for exactly this reason.
The forms, and what differs
Tablets are the most common starting point. Estradiol valerate and estradiol hemihydrate are the usual types. They're cheap and easy, but everything swallowed passes through the liver first, and that's what raises clot risk compared with the other routes.
Sublingual means letting a tablet dissolve under the tongue instead of swallowing it. More of the estradiol goes straight into the blood and less goes through the liver first. Levels rise faster and fall faster, so they swing more across the day. Some prescribers suggest it and some don't; ask before changing how you take a tablet.
Patches are stuck to the skin and changed once or twice a week. They're transdermal: the estradiol is absorbed through the skin and skips the liver's first pass. Levels are steady. Some people get skin irritation, and patches can peel off in heat, swimming or sweat.
Gel is rubbed into the skin daily, and is also transdermal. It gives steady levels, but it needs to dry before you dress, and skin contact with partners or children soon after applying is best avoided.
Injections go into muscle or under the skin every few days to every couple of weeks, depending on the type. They also skip the liver and can reach higher levels, which helps suppress testosterone without an anti-androgen. The tradeoff is a peak after each shot and a fall before the next, covered in blood levels. Availability varies a lot: common in parts of the US, less often prescribed in the UK. Injecting hormones covers the practical side.
Some UK prescribers also use implants, small pellets placed under the skin that release estradiol over months. They're uncommon now.
Before your first appointment
Think about which forms would actually fit your life, such as whether you'll remember a daily gel, whether patches will survive your job or your gym, and how you feel about needles. A prescriber can only work with what you'll actually take.
Why the route matters for blood clots
The main serious risk of estrogen is a blood clot, most often a deep vein thrombosis. Swallowed estrogen raises that risk more than estrogen through the skin or by injection, because of its first pass through the liver, where clotting proteins are made. Sublingual use sends less through the liver than swallowing, but it isn't generally treated as equivalent to a patch.
So if you're in a higher-risk group, older, a smoker, or with a past clot or a family history of them, expect a prescriber to steer you towards patches or gel, and possibly to move you across from tablets as you get older. For a healthy young non-smoker the absolute risk on estradiol is low, and tablets are a reasonable start. The route is one of the few risk levers you and your prescriber control directly. What else raises clot risk, and the warning signs, are in risks and side effects.
Blood levels
Your prescriber will check estradiol and testosterone in your blood, commonly about every three months in the first year and once or twice a year once things are stable, plus a few weeks to months after any change of dose or form. Blood tests and monitoring covers the full panel and schedule.
Guidelines give a target range rather than a single number. The Endocrine Society's guideline is the one most often cited: estradiol of roughly 100 to 200 pg/mL (about 370 to 730 pmol/L), with testosterone suppressed to under about 50 ng/dL (under about 1.7 nmol/L). Clinics interpret that differently, and many weigh how you feel and what's changing as heavily as the number. Higher estradiol isn't automatically better: past a point it adds risk without adding feminization.
The form you take changes how the number behaves. Patches and gel give fairly flat levels, so the time of the test matters less, though blood drawn from the arm you put gel on can read falsely high. Tablets peak a few hours after a dose, sublingual more sharply. Injections swing the most, from a peak a day or two after the shot to a trough just before the next, and many prescribers want the trough. How to read your hormone blood results covers the units and how to read the lab's flags.
Every time you have bloods taken
Note down when you last took your estrogen and how, and keep your results in one place. A prescriber seeing you for the first time, including a surgeon's team, will want that history, and labs don't always pass it on.
How long before it works
Skin, libido and mood can shift within weeks; breast growth usually begins within a few months and runs for two to three years or more. What changes, and when has the fuller timeline.
A higher dose doesn't make it go faster. The body develops on its own schedule, and levels above the target range mostly add clot risk. Steady levels in the target range are what deliver results, which matters especially if you manage your own hormones.
If you're getting estrogen outside a clinic
Some people take estrogen without a prescription, usually because a clinic is out of reach or the wait is years long. I'm not going to pretend it doesn't happen, and I'm not going to help with how.
What I would say is that the risks don't change because the source did. If you're in that position, get your blood tested, avoid ethinylestradiol and contraceptive pills, and see a clinician as soon as you can. Many informed-consent clinics will take over care for someone already on hormones, and some doctors will write a bridging prescription while you wait for a specialist.
Frequently asked questions
What's the best form of estrogen?
There isn't one best form. Tablets are simplest, patches and gel skip the liver and carry lower clot risk, and injections suit some people who want to avoid an anti-androgen. See the forms, and what differs.
Is estradiol the same as the contraceptive pill?
No. Most contraceptive pills contain ethinylestradiol, a synthetic estrogen with a higher clot risk that guidelines advise against for feminizing HRT. See estradiol, the estrogen prescribers use today.
Will a higher dose give me faster results?
No. Development follows its own pace, and levels above the target range mainly add risk. See how long before it works.
What should my estradiol level be?
Guidelines commonly cite a range rather than one number, roughly 100 to 200 pg/mL (about 370 to 730 pmol/L) in the Endocrine Society's guideline, and the timing of the test changes the result. Your prescriber sets your target. See blood levels.