Description
Estradiol Cypionate is the injectable cypionate ester form of the human estrogen estradiol. The substance is used clinically in Gender-Affirming Hormone Therapy (GAHT) for transgender women and in treatment of postmenopausal hormone deficits.
Per study reports Estradiol binds to estrogen receptors ERα and ERβ. Cellular effects include breast tissue development, bone density preservation, cardiovascular protective effects, skin structure changes, lipid profile modulation, and fat distribution shifts toward female pattern.
The cypionate ester form has a half-life of about 8 days, allowing weekly or biweekly injections. Steady-state is established after 3-4 weeks. Compared to oral estradiol administration (Estradiol Valerate tablets), injection has two advantages: bypass of first-pass hepatic metabolism (substantially lower thrombosis risk) and more stable plasma levels.
In recreational research practice Estradiol Cypionate is primarily used in two contexts: GAHT research setups and HRT research protocols for postmenopausal users. A rare application in anabolic research is as E2 boost when a cycle has inadvertently run too E2-low (through too-aggressive AI use).
Known effects in studies: dose-dependent feminizing effects (breast development, fat redistribution, skin changes), elevated thromboembolism risk (substantially lower than under oral estradiol), HPG suppression (especially testosterone lowering in male users).
You can order Estradiol Cypionate as an oily injection solution in 10-pack at 10mg/ml.
This information is for research and educational purposes only. No medical recommendations.
Risks & Safety
Estradiol Cypionate is an estrogen, not an androgen - the risk profile described in the literature is estrogen-driven and differs fundamentally from anabolics. The injectable form is considered lower in thrombosis risk compared to oral estradiol because first-pass hepatic metabolism is bypassed.
Documented in studies and the application literature:
- Thromboembolism risk: Estradiol elevates the risk for thromboembolism. A substantially lower risk than under oral estradiol is documented, but not a zero risk.
- Feminizing effects: studies describe dose-dependent feminizing effects such as breast tissue development, fat redistribution toward female pattern and skin structure changes. In male users these effects are in part not reversible.
- HPG suppression: Estradiol suppresses the HPG axis, and in male users a marked lowering of endogenous testosterone is documented.
- Other: the literature describes prolactin elevation under higher E2 doses as well as effects on the lipid profile and bone density.
Baseline bloodwork before, during and after a research protocol is strongly advised. This classification does not replace medical advice. Risk and responsibility for any actual use lie entirely with the buyer.
Studies
- Endocrine treatment of gender-dysphoric/gender-incongruent persons: an Endocrine Society clinical practice guideline - JCEM 2017, Hembree et al: guideline on GAHT including estradiol dosing and monitoring.
- Stability of weekly intramuscular estradiol cypionate in a transgender woman - Journal of the Endocrine Society 2021, Madison et al: serum stability data under weekly IM application.
- Does the route of administration for estrogen hormone therapy impact the risk of venous thromboembolism? - Menopause 2011, Canonico et al: compares thromboembolism risk between oral and transdermal administration.
- Lunelle monthly contraceptive injection (medroxyprogesterone acetate and estradiol cypionate injectable suspension): effects of body weight and injection sites on pharmacokinetics - Contraception 1999, Rahimy et al: pharmacokinetics of injectable estradiol cypionate.
- Medroxyprogesterone acetate and estradiol cypionate injectable suspension (Cyclofem) monthly contraceptive injection: steady-state pharmacokinetics - Contraception 2013, Garza-Flores et al: steady-state data of cypionate injection.
