Anastrozole: what it does, how to take it, and what to watch for

Anastrozole is an aromatase inhibitor most commonly used to treat hormone receptor–positive breast cancer in postmenopausal women. It lowers estrogen production in the body, which helps slow or stop the growth of certain tumors. People also encounter anastrozole off-label — for example, men using it to manage high estrogen from testosterone therapy — but that comes with different risks and monitoring needs.

How it’s usually taken and typical doses

For breast cancer, the standard adult dose is 1 mg by mouth once a day. Doctors may prescribe it for several years after initial therapy to reduce recurrence risk. Off-label dosing varies a lot: men or bodybuilders sometimes use 0.5–1 mg every other day or 0.5 mg daily, but that’s not medical advice — it’s risky without medical supervision. Always follow a prescriber’s instructions and don’t self-adjust the dose.

Side effects, monitoring, and safety tips

Common side effects include joint and muscle pain, hot flashes, fatigue, and nausea. Because anastrozole lowers estrogen, it can reduce bone density over time — so doctors often check bone density (DEXA scan) before and during long-term use. Watch for mood changes, new or worsening joint pain, or signs of allergic reaction. If you’re pregnant or might become pregnant, don’t take anastrozole — it can seriously harm a fetus.

Lab checks may include bone health, lipid profile, and sometimes liver tests. If you’re a man using anastrozole to control estrogen, your clinician should monitor testosterone and estradiol levels, because over-suppressing estrogen can lower libido, cause mood shifts, and harm bone health.

Drug interactions are not extensive but matter: tell your provider about all prescription meds, supplements, and herbal products. Estrogen-containing therapies will oppose anastrozole’s effect. Also mention blood thinners and strong liver enzyme modifiers so your provider can watch for changes.

Thinking about alternatives? Tamoxifen works differently (it blocks estrogen receptors) and may suit premenopausal women better. Other aromatase inhibitors include letrozole and exemestane; each has pros and cons your doctor can compare with you.

Where to get it: anastrozole requires a prescription in most countries. Use a licensed pharmacy and verify prescriptions through a doctor. Avoid unverified online sellers — counterfeit medicines are a real risk.

Quick checklist before you start anastrozole: confirm menopause status if you’re a woman, review bone health history, list current meds and supplements, and plan regular follow-up labs. If anything feels off while you’re on treatment, call your provider — catching issues early keeps treatment safer and more effective.