Anastrozole in men: an off-label option, used sparingly
Anastrozole is an aromatase inhibitor. It is FDA-approved for breast cancer in postmenopausal women, not for men. Some physicians prescribe it off-label when estradiol is high on testosterone therapy, but routine use is not supported by the evidence, and the first step is almost always a change in the testosterone plan.
Information current as of November 10, 2026. Educational only. Confirm everything here with your own clinician before starting, stopping or changing any medication.
At a glance
Drug class
Aromatase inhibitor. It blocks the enzyme that converts testosterone into estradiol.
How it is taken
A tablet by mouth. The labeled dose for its approved use in women is one 1 mg tablet once daily. Doses in men are individualized and off-label.
Approval status
FDA-approved only for breast cancer in postmenopausal women. Use in men is off-label.
Who it is for
A small number of men on testosterone therapy who have bothersome symptoms of high estradiol that did not settle after the testosterone plan was adjusted.
Main cautions
Lower bone density, higher cholesterol, joint pain and low mood have been reported. Estradiol also protects bone and sexual function in men, so lower is not better.
What it is
What anastrozole does, and why a man’s body needs some estradiol
Aromatase is an enzyme that turns testosterone into estradiol, a form of estrogen. Body fat contains a lot of it. Testosterone therapy gives the enzyme more testosterone to work on, so estradiol often rises along with testosterone. Anastrozole blocks the enzyme, which lowers estradiol and can raise testosterone a little.
Men need estradiol. In a 16-week study of 400 healthy men aged 20 to 50, researchers shut down the men’s own testosterone and estradiol, gave testosterone gel at several doses, and in half the men also blocked the conversion to estradiol with anastrozole. Estrogen deficiency mainly accounted for increases in body fat, and both testosterone and estrogen deficiency contributed to the drop in sexual function (Finkelstein 2013, see sources). Lowering estradiol too far has a cost.
The other hormone therapy pages for men are testosterone, clomiphene and hCG. Our men’s page covers how these fit with weight management.
Approval
What the FDA label covers, and what it does not
The Arimidex label lists three uses, all in postmenopausal women with hormone receptor-positive breast cancer: adjuvant treatment of early disease, first-line treatment of advanced disease, and treatment of advanced disease that progressed after tamoxifen. The dose is one 1 mg tablet once a day, with or without food.
The label does not list low testosterone, high estradiol, gynecomastia or male infertility. Using anastrozole for any of those in men is off-label. It is legal for a physician to prescribe, and the FDA has not reviewed it for that purpose. Every safety number on the label comes from women with cancer, which limits how far it applies to men.
The evidence
What studies of aromatase inhibitors in men show
The best-known trial gave 1 mg of anastrozole daily or placebo to 69 men aged 60 or older with borderline or low testosterone for one year (Burnett-Bowie 2009). Testosterone rose from an average of 319 to 524 ng/dL at three months and was 474 at one year. Estradiol fell from 15 to 12 pg/mL. Spine bone density dropped in the anastrozole group compared with placebo. The authors concluded that aromatase inhibition does not improve skeletal health in aging men with low or low-normal testosterone.
That trial studied older men who were not on testosterone, so it does not map neatly onto a man on injections. It does show a real bone signal. A 2014 review of aromatase inhibitors in adult men describes interest in the testosterone-to-estradiol ratio, and also reviews bone effects and the limits of the available data.
Our own reading of the evidence is simple. We have not found a trial showing that routinely adding anastrozole to testosterone therapy improves symptoms or outcomes. That is why we say routine use is not supported, and why this page says sparingly.
What the label shows in women, and why it matters here
- Bone: the label states that because anastrozole lowers circulating estrogen it may reduce bone mineral density.
- Lipids: the label reports that mean total cholesterol rose by 0.5 mmol/L in women taking anastrozole, while a later 12-month study in women found no clinically significant change in LDL, HDL or triglycerides. The data are mixed.
- Heart: in women with existing ischemic heart disease, ischemic events were 17 percent on anastrozole versus 10 percent on tamoxifen.
- Mood and joints: depression, insomnia, joint pain and hot flashes are among the common adverse reactions.
What we do first
High estradiol on testosterone: adjust the testosterone first
A high estradiol result is not a reason to start a drug. We look at symptoms first: breast tenderness, swelling, fluid retention, mood swings or lower libido. Then we check what is driving the number.
- The testosterone dose. A lower dose or a different schedule often lowers both testosterone peaks and estradiol. Smaller, more frequent injections can smooth peaks.
- The timing of the lab draw. A level drawn at the peak after an injection reads differently from a trough level.
- Body fat. Fat tissue makes aromatase. Weight management is part of the plan, which is one reason a men’s plan can include a GLP-1.
- Alcohol and other medicines. Both can change hormone levels.
If symptoms persist after those steps, a short, low-dose trial of an aromatase inhibitor may be considered. A trial has a stated goal and an end date. Doses and schedules are individualized by your physician.
Monitoring
What we watch if anastrozole is used
- Total testosterone and estradiol about 4 to 6 weeks after starting or changing a dose, to see whether estradiol is being pushed too low.
- Bone health. The label says bone status should be managed according to guidelines in women starting anastrozole, so a bone density scan is a reasonable baseline in a man with other risk factors.
- Lipid panel, because the label reports cholesterol increases in women.
- Mood, sleep, joint pain and sexual function at each visit.
The label also says estrogen-containing products can reduce anastrozole’s effect and should not be combined with it. If you are on any other hormone, tell us.
If estradiol falls below your usual range or symptoms get worse, the plan is to stop and recheck, not to add another drug.
Summit’s role
What Summit does with anastrozole
Dr. Miranda decides whether this fits you after your history and labs. Summit is telehealth only. Testosterone for men follows state telehealth rules and requires symptoms plus two morning total testosterone readings below 300. It is a Schedule III controlled substance. Anastrozole is a separate decision, made only after the testosterone plan has been adjusted, and nothing here promises that it will be prescribed.
Labs are included with Summit plans. See pricing for details.
Common questions
Questions people ask
Is anastrozole FDA-approved for men?
No. The FDA label covers breast cancer in postmenopausal women. Using it in men for high estradiol on testosterone therapy is off-label, and the physician decides whether it fits.
Why not just lower my estradiol with anastrozole?
Men need some estradiol for bone, sexual function and body composition. In a trial of older men, one year of anastrozole lowered spine bone density compared with placebo. We adjust the testosterone plan first.
How do you treat high estradiol without an aromatase inhibitor?
By changing the testosterone dose or schedule, checking lab timing, and addressing body fat and alcohol. Symptoms decide, not one number.
How long would a man stay on anastrozole?
If it is used, it is a short trial with a goal and an end date. Long-term safety data in men are limited.
What side effects does anastrozole have?
The label, written from studies in women, lists hot flashes, joint pain, weakness, depression, insomnia, headache, bone loss and higher cholesterol. Rare allergic reactions can occur.
Sources
Where this comes from
All retrieved November 10, 2026.
- Arimidex (anastrozole) prescribing information. DailyMed. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=acbfaaa9-503c-4691-9828-76a7146ed6de
- Burnett-Bowie SA et al. Effects of aromatase inhibition on bone mineral density and bone turnover in older men with low testosterone levels. J Clin Endocrinol Metab 2009. https://pubmed.ncbi.nlm.nih.gov/19820017/
- Finkelstein JS et al. Gonadal steroids and body composition, strength, and sexual function in men. N Engl J Med 2013. https://pubmed.ncbi.nlm.nih.gov/24024838/
- Tan RB et al. Clinical use of aromatase inhibitors in adult males. Sex Med Rev 2014. https://pubmed.ncbi.nlm.nih.gov/27784593/
- Bhasin S et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab 2018. https://pubmed.ncbi.nlm.nih.gov/29562364/
- Mulhall JP et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. J Urol 2018. https://pubmed.ncbi.nlm.nih.gov/29601923/
Confirm with your provider. This page is general education, not medical advice, and it does not diagnose or treat anything. Every medication carries risks and is not right for everyone. Medication is prescribed only after a physician evaluation determines it is appropriate for you. Individual results vary and no outcome is guaranteed. Information current as of November 10, 2026.
Next step
Start with the testosterone plan, not the add-on
Dr. Miranda reviews your symptoms and labs first. Whether any adjunct fits is decided after that.