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Estradiol Cypionate (Injection)

HRTprescriptionim · inferred

Longest-acting injectable estradiol ester. Duration ~11-14 days per injection. Slower peak (~day 4) and more stable levels than valerate. Used in menopause HRT and feminizing therapy. Typical dosing: 2-10 mg IM every 1-2 weeks.

Projected serum levels — 5 mg, weekly

Estradiol Cypionate (Injection) (precursor)
Estradiol Cypionate (Injection) modeled serum levels, 5 mg weekly over 63 days Population-based pharmacokinetic estimate. Steady state reached after approximately 28 days. 0 0.25 0.50 0.75 1 Day 0 Day 16 Day 32 Day 47 Day 63 Time on a regular schedule ≈ steady state · day 28
Estradiol Cypionate (Injection) modeled serum levels with a loading dose of 10.9 mg, then 5 mg weekly The first dose is larger so levels approach steady state faster. 0 0.25 0.50 0.75 1 Day 0 Day 16 Day 32 Day 47 Day 63 Time on a regular schedule

Maintenance schedule: 5 mg weekly (im).

Loading schedule: 10.9 mg on day 1, then 5 mg weekly — reaching therapeutic levels sooner.

Modeled steady state after ~28 days: peak ≈ 0.039 mg, trough ≈ 0.021 mg body load. Population-based estimate over 63 days for a 5 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
HRT
Route modeled
IM
Model confidence
inferred
Half-life
8 days
Common dose
5 mg
Suggested maximum
10 mg/day
Reference dose range
2–10 mg (single dose)
Suggested cadence
weekly
Validated against
5 mg im — Cmax 0.000 mg/L at 96 h

Documented interactions

  • danger
    Carbamazepine (Tegretol) + Estradiol Cypionate (Injection) CYP induction

    Carbamazepine (Tegretol) inducer of CYP3A4 predicted to change Estradiol Cypionate (Injection) AUC by ~0.49x

  • danger
    Efavirenz (Sustiva) + Estradiol Cypionate (Injection) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Estradiol Cypionate (Injection) AUC by ~0.35x

  • danger
    Levothyroxine (Synthroid) + Estradiol Cypionate (Injection) Protein binding

    Estradiol Cypionate (Injection) may displace Levothyroxine (Synthroid) from plasma protein binding sites, transiently raising free drug concentration. This drug has a narrow therapeutic index; free…

  • danger
    Rifampin + Estradiol Cypionate (Injection) CYP induction

    Rifampin inducer of CYP3A4 predicted to change Estradiol Cypionate (Injection) AUC by ~0.35x

  • danger
    Tacrolimus (Prograf) + Estradiol Cypionate (Injection) Protein binding

    Estradiol Cypionate (Injection) may displace Tacrolimus (Prograf) from plasma protein binding sites, transiently raising free drug concentration. This drug has a narrow therapeutic index; free…

  • danger
    Warfarin (Coumadin) + Estradiol Cypionate (Injection) Protein binding

    Estradiol Cypionate (Injection) may displace Warfarin (Coumadin) from plasma protein binding sites, transiently raising free drug concentration. This drug has a narrow therapeutic index; free…

Serum checks 231 modeled interaction pairings for estradiol cypionate (injection) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. A Comparison of the Pharmacokinetic Properties of Three Estradiol Esters Oriowo MA et al. · Journal of Steroid Biochemistry, 1980 DOI

    Showed estradiol cypionate maintains elevated levels for ~11 days with peak at day 4, the longest duration among common estradiol esters.

  2. Overview of Feminizing Hormone Therapy UCSF Center of Excellence for Transgender Health · Transgender Care Guidelines, 2016 DOI

    Clinical guidelines for estradiol cypionate dosing in feminizing therapy: 2-10 mg IM every 1-2 weeks targeting serum E2 100-200 pg/mL.

  3. Hormone Therapy in Transgender Adults Is Safe with Provider Supervision Weinand JD, Safer JD · Journal of Clinical & Translational Endocrinology, 2015 DOI

    Safety review of injectable estradiol in transgender women showing acceptable cardiovascular and thromboembolic risk with appropriate monitoring.

3 published studies referenced in the app, each with a plain-language summary.