Depo-Estradiol is an injectable form of estrogen given as an intramuscular shot, typically every three to four weeks. Its active ingredient is estradiol cypionate, a long-acting version of the estrogen your body naturally produces. It’s FDA-approved to treat hot flashes and other vasomotor symptoms of menopause, as well as low estrogen caused by conditions where the ovaries don’t produce enough hormones on their own. It’s also widely used in feminizing hormone therapy for transgender women.
How It Works
Estradiol cypionate is estradiol attached to a fatty acid chain, dissolved in an oil-based solution. When injected into muscle tissue, the oil creates a small depot (a reservoir) that slowly releases the hormone over days to weeks. Once released, enzymes in the liver strip away the fatty acid chain, leaving behind plain estradiol, the same hormone the ovaries produce.
The cypionate ester has a longer fatty acid chain than some other injectable estrogen formulations, which makes it more fat-soluble. That translates to a slower, steadier release. After a 5 mg injection, blood levels typically peak between days two and four, reaching roughly 222 to 340 pg/mL, and the effects last about 14 to 18 days. For comparison, the same dose of estradiol valerate (a shorter-chain ester) peaks higher, around 400 to 667 pg/mL, and hits that peak faster, around day two. So cypionate produces a lower, more drawn-out curve, which some people and clinicians prefer for more stable hormone levels.
FDA-Approved Uses
Depo-Estradiol carries two official indications. The first is moderate to severe vasomotor symptoms of menopause: hot flashes, night sweats, and the flushing episodes that follow a drop in natural estrogen. The second is hypoestrogenism due to hypogonadism, meaning abnormally low estrogen because the ovaries are underactive or absent, whether from a genetic condition, surgical removal, or another cause.
For menopausal symptoms, the FDA-labeled recommendation is to start hormone therapy within 10 years of menopause onset or before age 60. The labeling also advises using the lowest effective dose and reassessing every three to six months whether the medication is still needed.
Use in Feminizing Hormone Therapy
Outside its FDA-labeled indications, estradiol cypionate is one of the most common injectable estrogens prescribed for transgender women and transfeminine individuals. UCSF’s guidelines list a starting dose of 2 mg injected weekly, with a low-start option of 1 mg weekly for those who want a slower transition or have medical reasons to begin cautiously. The maximum listed dose is 5 mg weekly, though guidelines note that maximum effect doesn’t require maximum dosing. Dose adjustments are based on how a person responds physically and what their blood levels show.
In gender-affirming care, the injection schedule is typically weekly rather than every three to four weeks as labeled for menopausal use. This more frequent dosing keeps estradiol levels steadier and within the range needed for feminization, including breast development, fat redistribution, and softening of skin.
Dosage and Availability
Depo-Estradiol comes in a 5 mL multi-dose vial at a concentration of 5 mg per mL. Your prescribed dose determines how much you draw from the vial each time. For menopausal symptoms, the usual range is 1 to 5 mg injected every three to four weeks. For feminizing hormone therapy, doses and frequency vary based on individual goals and lab results.
Pfizer manufactures the brand-name product and, as of late 2024, is the sole supplier. Availability has fluctuated over the years, with periodic shortages reported. If your pharmacy can’t fill the brand name, compounding pharmacies can prepare estradiol cypionate from raw ingredients, though insurance coverage for compounded versions varies.
How to Give the Injection
Depo-Estradiol is injected into a large muscle. The two most common sites are the outer middle third of the thigh (the vastus lateralis) and the upper outer quarter of the buttock (the gluteus maximus), roughly where a back pants pocket sits. The thigh is generally easier if you’re injecting yourself.
The basic process involves drawing the medication from the vial with a larger gauge needle (typically 18G), then switching to a smaller injection needle before injecting. You first pull air into the syringe equal to your dose volume, push that air into the vial to equalize pressure, then invert the vial and draw the medication. Tapping the syringe gently pushes air bubbles to the top so you can expel them before injecting. Clean the injection site with an alcohol swab, insert the needle at a 90-degree angle, and push the plunger slowly. Dispose of needles in a sharps container without recapping them.
Because the medication is oil-based, it can be thick and slow to draw. Warming the vial briefly in your hands or under warm water can help the oil flow more easily through the needle.
Storage
Store the vial at room temperature, between 68°F and 77°F. Don’t refrigerate it. If the vial has been exposed to cooler temperatures and you notice small crystals in the oil, warming it gently and shaking should dissolve them. Don’t use medication that’s expired, discolored, or contains visible particles that won’t dissolve.
Safety Considerations
Like all systemic estrogen products, Depo-Estradiol carries warnings about endometrial cancer risk for people who still have a uterus. Taking a progestogen alongside estrogen significantly reduces this risk, which is why combined therapy is standard for anyone with an intact uterus using systemic estrogen.
Earlier labeling included boxed warnings about cardiovascular disease, breast cancer, and dementia, but the FDA has moved to remove those warnings based on updated evidence. The agency now emphasizes that labeling should reflect current, balanced information about benefits and risks rather than the older, more alarming framing that was largely based on a single study of older postmenopausal women. The timing of when you start hormone therapy relative to menopause matters significantly for the risk profile, which is part of why the recommendation to begin within the first 10 years exists.
People with a history of blood clots, stroke, estrogen-sensitive cancers, or liver disease should discuss those conditions with their prescriber before starting any estrogen therapy, as these remain contraindications for use.