Should I Take Anastrozole with Testosterone? (2024)

About the Experts

Amarnath Rambhatla, M.D., is a board-certified urologist and member of the American Urologic Association. He is the Director of Men’s Health at the Henry Ford Vattikuti Urology Institute, where he specializes in low testosterone and hormone replacement therapy.

James R. Staheli, D.O., is the Medical Director for Broad Health, Hone Health’s affiliated medical practice, and a family medicine doctor, with a specialization in men’s hormone health.

What Is Anastrozole?

Anastrozole is an aromatase inhibitor, a medication that blocks an enzyme called aromatase from converting testosterone into estrogen.

“All men have this aromatase enzyme, which converts some of their testosterone into estrogen—particularly estradiol,” Amarnath Rambhatla, M.D., explains. If you’re on testosterone replacement therapy (TRT) to treat low T—essentially flooding your system with more T than you make naturally—your aromatase enzymes also produce more estrogen, raising your levels of both hormones.

Anastrozole, which comes in a pill form, allows your doctor to tweak your estrogen without touching your newly-optimized T levels.

Adding Anastrozole to Testosterone

When you’re prescribed TRT, your doctor should monitor your hormone levels every few months to make sure they are within a healthy range. If your estrogen shoots above the healthy range for men—10 to 40 pg/ml of estradiol and 10 to 60 pg/ml of estrone per the Endocrine Society—you may experience a frustrating swap of low T symptoms for ones associated with too-high estrogen. High estrogen can cause symptoms like breast tissue growth (man boobs), erectile dysfunction, and fatigue. It’s also been linked to prostate and breast cancer and blood clots.

“I usually wait until someone comes to me with symptoms of high estrogen before I prescribe anastrozole,” says Rambhatla.

He’s in good company: Up to 70 percent of doctors prescribe an aromatase inhibitor like anastrozole to men who are showing symptoms of high estrogen on TRT, according to a survey of members of the International Society of Sexual Medicine (1). Around 48 percent of those doctors also prescribe an aromatase inhibitor to men who have high estrogen without symptoms. Just 14 percent offer it as a preventative measure to men starting TRT.

Hone customer Jonathan Potter experienced water retention and slight muscle weakness shortly after starting TRT. When his 3-month check-up revealed his estrogen was high, his doctor added anastrozole to balance his hormones. “The water weight went away,” Potter says. “My strength increased more rapidly, too. I’m a lot more satisfied with how I feel after adding [anastrozole] to my TRT protocol.”

Dosing

Most men who are prescribed anastrozole start on a low dose, twice a week, Rambhatla says. Although, dosing varies from person to person. It’s typically taken the day of or the day after their TRT dose if they’re on twice-weekly injections—one of the most common TRT regimens.

“If your estrogen levels dip below 20 pg/ml, your doctor may drop the dose to one milligram once a week, sometimes cycling it on and off for a couple of months,” Rambhatla says.

Staheli and Rambhatla emphasize that you should never try to cycle your dose or take anastrozole or any other aromatase inhibitor on your own. Accidentally driving your estrogen levels into the ground can have some serious health consequences. (More on that later.)

Do All Men on Testosterone Need Anastrozole?

While research shows that anastrozole effectively controls high estrogen for men on TRT (2), not all doctors think elevated estrogen is a problem. Adding to the confusion: Some medical societies, including The Endocrine Society, don’t provide guidance on anastrozole for hormone therapy (3), leaving it up to doctors to decide.

“Many clinics downplay the use of anastrozole, noting the need for all men to enjoy the benefits of estrogen such as preserving bone health, muscle development, and brain function,” Staheli says. “While that is true, we cannot understate the [negative] effects of high estrogen levels.”

Symptoms of high estrogen in men include:

• Infertility
• Gynecomastia (man boobs)
• Erectile dysfunction
• Decreased libido
• Fatigue
• Muscle atrophy
• Mental fog
• Water retention

Other doctors argue that high estrogen should be managed by lowering the dose of testosterone, instead of adding another medication (1). But here’s where that thinking hits a snag: If your testosterone levels have been raised into an optimal range—relieving your symptoms—bringing down your dose might cause some of them to come back, according to Staheli.

Can You Take Anastrozole Without Testosterone?

While anastrozole is most commonly prescribed in conjunction with testosterone, some men are prescribed the drug on its own.

“If you have high estrogen levels and are experiencing symptoms such as gynecomastia (man boobs), despite having healthy testosterone levels, anastrozole might be a great treatment option,” Staheli explains.

Side Effects

Anastrozole can cause side effects while your body adjusts, including:

• Hot flashes
• Dizziness
• Blurred vision
• Nervousness
• Muscle weakness

These side effects often go away after a few months of treatment. If you’re prescribed the drug and they persist, says Rambhatla, your doctor may lower your dose or opt for other hormone therapy protocols.

Some doctors shy away from prescribing anastrozole because of the long-term risks if your estrogen drops too low, including loss of bone density.

“The main thing we worry about is that [anastrozole] can potentially decrease bone mineral density,” Rambhatla says. “If we don’t monitor your levels closely, your bone health gets affected.”

That said, if you start anastrozole and your estrogen plummets, don’t stress: Research shows that it takes between one and five years of sustained low estrogen (below 10 pg/ml) to significantly impact bone health (4). Your doctor can address the problem before that happens.

Can Anastrozole Help with ED?

Having too much estrogen may be bad for your erections (5). A 2020 study found that men struggling with erectile dysfunction had elevated estradiol levels compared to men who didn’t have ED (6).

Does that mean that anastrozole can help with ED? Possibly, but researchers say there’s not enough evidence to make the drug a first-line defense against erectile dysfunction (7).