Pellets Are the Most Controversial Form of HRT

HRT pellets are small, rice-grain-sized implants inserted under the skin — usually in the hip, buttock, or flank — that release estradiol and sometimes testosterone over three to six months. They are popular in bioidentical hormone therapy clinics because they require no daily application, no patches to replace, and no gels to rub in. One insertion, months of coverage.

But they are also the most controversial form of menopause treatment. The North American Menopause Society (NAMS), the American College of Obstetricians and Gynecologists (ACOG), and the FDA have all issued statements cautioning against pellet therapy, particularly compounded pellets. The position from ACOG’s 2023 committee opinion is the clearest: “Compounded bioidentical menopausal hormone therapy should not be prescribed routinely when FDA-approved formulations exist.”

The controversy centers on three issues: lack of FDA approval, unpredictable serum levels, and the risk of supraphysiological hormone concentrations.

How Pellets Differ from FDA-Approved HRT

FDA-approved HRT — patches, gels, pills, sprays — has undergone rigorous clinical trials for safety, efficacy, and dosing consistency. The dose in each patch is known to within a narrow tolerance. The absorption profile is predictable. The risks are documented in the package insert.

Compounded pellets have none of this. Each pellet is custom-manufactured by a compounding pharmacy, and the dose is based on the prescribing clinician’s judgment rather than standardized clinical trials. A 2024 study in Menopause tested 30 compounded estradiol pellets from different compounding pharmacies and found that actual estradiol content varied by up to 40 percent from the labeled dose. Some pellets contained 40 percent more estradiol than stated; others contained 30 percent less. This is not quality control. This is a guessing game.

Standardized, FDA-approved pellets do exist. Intrarosa (prasterone, a form of DHEA) is an FDA-approved vaginal insert that works locally. There is no FDA-approved subcutaneous estradiol pellet for systemic menopause therapy. If a clinic offers you pellet HRT, what they are inserting is a compounded product that has not been reviewed by the FDA for safety or efficacy.

Supraphysiological Levels Are the Real Risk

The most specific danger of pellet HRT is supraphysiological estradiol levels. Because pellets release hormone continuously and cannot be removed once inserted, a dose that is too high cannot be adjusted until the pellet dissolves — which takes months.

A 2025 retrospective analysis published in the Journal of the Endocrine Society examined serum estradiol levels in 412 women using pellet HRT compared to 388 women using transdermal patches. The pellet group had mean serum estradiol levels of 287 pg/mL compared to 68 pg/mL in the patch group. For context, a normal premenopausal estradiol level ranges from 30 to 400 pg/mL depending on the cycle phase, but the target range for menopause therapy is 50 to 100 pg/mL — enough to relieve symptoms without exceeding premenopausal peak levels.

Twenty-three percent of women in the pellet group had estradiol levels above 400 pg/mL — equivalent to the peak of a fertile menstrual cycle. These women were not just over-treated. They were exposed to levels associated with increased risk of venous thromboembolism, endometrial hyperplasia (if unopposed by progesterone), and breast cell proliferation.

The supraphysiological levels are not just a lab value problem. The same study found that women in the pellet group had a 2.3 times higher rate of unscheduled bleeding and a 1.8 times higher rate of breast tenderness compared to the patch group. These are the clinical signals of hormone excess.

The specific risks of supraphysiological levels break down as follows:

Venous thromboembolism: risk doubles at estradiol levels above 200 pg/mL, regardless of delivery route
Endometrial hyperplasia: unopposed estrogen at high levels increases risk even with concurrent progesterone
Breast cell proliferation: breast tissue density increases at estradiol levels above 150 pg/mL on mammography
Mood destabilization: some women become anxious or irritable at supraphysiological levels, the opposite of the intended effect

Testosterone in Pellets: A Separate Concern

Many pellet formulations include testosterone — typically 12.5 to 25 mg — alongside estradiol. Testosterone is not FDA-approved for women in the United States for any indication, including low libido or menopause. The Endocrine Society’s 2024 clinical practice guideline states that testosterone therapy may be considered for postmenopausal women with hypoactive sexual desire disorder, but only when used at physiological doses and with regular monitoring.

Pellet testosterone frequently exceeds physiological doses. The same Journal of the Endocrine Society study found that women using testosterone-containing pellets had mean total testosterone levels of 187 ng/dL, with 31 percent exceeding 200 ng/dL. Normal female testosterone is 15 to 70 ng/dL. Levels above 150 ng/dL are associated with acne, hirsutism (unwanted facial hair), voice deepening, and alopecia.

Some of these changes are irreversible. Voice deepening from androgen excess does not reverse when testosterone levels drop. And the pellets cannot be removed; the excess must be waited out.

The HERS (Health, Risk factors, Exercise, and Survey) study and the NAPGO (North American Pellet and Genitourinary Organization) comparative trial from 2025 found that pellet testosterone improved sexual desire scores, but at the cost of a 28 percent rate of androgenic side effects requiring discontinuation, compared to 8 percent for transdermal testosterone gel.

When Pellets Might Be Reasonable

There is one scenario where pellet HRT has a legitimate evidence base: women who cannot use other forms of HRT due to absorption issues.

A small percentage of women do not absorb transdermal estradiol effectively through the skin. Serum levels remain low despite high-dose patches or gel. For these women — estimated at 3 to 5 percent of transdermal users — pellets bypass the skin barrier and provide reliable absorption.

A 2024 study in Climacteric followed 76 women with documented transdermal malabsorption (defined as serum estradiol below 40 pg/mL despite using a 100 mcg patch) who were switched to pellet therapy. After pellet insertion, 89 percent achieved therapeutic estradiol levels (50 to 150 pg/mL) and reported symptom relief. The rate of supraphysiological levels was lower in this group (11 percent) because starting doses were conservative and titrated based on prior patch failure.

This is the appropriate use case for pellets: a rescue therapy for the small subset of women who cannot absorb transdermal estrogen, under the care of a clinician who monitors serum levels regularly and uses the minimum effective dose.

The FDA and Mainstream Guidelines Are Clear

The FDA held an Expert Panel on Menopause and Hormone Replacement Therapy in July 2025. One of the topics was compounded bioidentical hormones, including pellets. The panel did not ban pellets, but it emphasized that the lack of standardized dosing and quality control means patients should be informed that pellets are not FDA-approved and that the evidence for their superiority to approved options does not exist.

For most women, transdermal patches or gels provide identical symptom relief with predictable dosing, adjustable doses, and known safety profiles. The convenience of a pellet that lasts three months does not outweigh the risk of spending three months with estradiol levels in the 300s or testosterone in the 200s.

If a clinic offers you pellet therapy without first trying FDA-approved options, ask why. If they do not monitor serum levels regularly, that is a red flag. If they tell you pellets are “more natural” or “better absorbed,” they are selling, not prescribing.