Anastrozole
Arimidex / AI
A potent aromatase inhibitor used to manage estrogen levels in men on testosterone therapy. Prevents estrogen-related side effects like gynecomastia and water retention. Requires careful dosing to avoid crashing estradiol.
Half-life
46–50 hours
Typical Dose
0.25–0.5 mg 2–3x/week
0.3/0.5Route
oral
Category
sexual_health
Evidence Overview
Strength of evidence across clinical, expert, and experimental lanes.
How Anastrozole is dosed in practice
Usually taken by mouth. Typical range: 0.25–0.5 mg 2–3x/week. Half-life: 46–50 hours. Each card gives the dose, frequency and duration from one evidence lane: Clinical (human trials), Expert (practitioner protocols) or Experimental (early or animal data). These ranges describe what has been studied or used; they are not a prescription.
Work out the units to draw with the reconstitution calculator, how long a vial lasts with the vial duration calculator, and how levels fall between doses with the half-life calculator.
Approved at 1 mg daily for breast cancer in postmenopausal women. One randomized trial (2004) in older men not on TRT found that 1 mg twice weekly raised testosterone and lowered estradiol about as much as 1 mg daily. No trial has tested 0.25–0.5 mg two to three times weekly alongside TRT.
- Drug label (Arimidex)
- Randomized trial in older men (2004)
Modern TRT practitioners use AI sparingly — only for symptomatic high estradiol. Many advocate 'no AI' protocols with optimized injection frequency. When needed, 0.25 mg twice weekly is typical starting point.
- Leading practitioners — estrogen management
- Hormone-replacement clinical framework on estrogen management
- TRT practitioner consensus on minimal AI use
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Upgrade to ProSafety & Contraindications
- Osteoporosis or low bone density (chronic use reduces estrogen)
- Pre-menopausal women (unless clinically indicated)
- Known hypersensitivity to anastrozole
Anastrozole: common questions
What is Anastrozole?
A potent aromatase inhibitor used to manage estrogen levels in men on testosterone therapy. Prevents estrogen-related side effects like gynecomastia and water retention. Requires careful dosing to avoid crashing estradiol.
How is Anastrozole dosed?
Anastrozole is usually taken by mouth. Typical range in DoseCraft's library: 0.25–0.5 mg 2–3x/week. Clinical (human trials): 1 mg daily (label, breast cancer); 1 mg daily or twice weekly in older men with low testosterone not on TRT; Once daily (label); twice weekly in one 12-week trial; 12 weeks in the male trial; years for breast cancer. Expert (practitioner protocols): 0.125–0.5 mg per dose; 1–3x per week (symptom-guided); As needed — minimize chronic use. These ranges describe what has been studied or used; they are not a prescription.
Is Anastrozole FDA-approved?
Yes. Anastrozole is an FDA-approved prescription medicine; uses outside its approved indication are off-label.
What is the half-life of Anastrozole?
DoseCraft's library lists a half-life of 46–50 hours. Half-life sets how often a compound is dosed and how long it takes to clear: about five half-lives.
Who should not use Anastrozole?
Listed contraindications: Osteoporosis or low bone density (chronic use reduces estrogen); Pre-menopausal women (unless clinically indicated); Known hypersensitivity to anastrozole.
Information is for educational purposes only. Always consult a licensed healthcare provider before starting any peptide regimen.
Page updated . How we grade evidence: methodology.