Enclomiphene vs Clomiphene (Clomid): Key Differences

The core of the enclomiphene vs clomiphene (Clomid) question is chemistry: clomiphene citrate is a single drug made of two mirror-image isomers, and enclomiphene is one of them. Clomid is the brand most people recognize, a selective estrogen receptor modulator (SERM) that is FDA-approved only for ovulatory dysfunction in women desiring pregnancy. Enclomiphene is the trans-isomer purified from that mixture. It is not FDA-approved for any use, is dispensed as a compounded preparation, and the FDA has not evaluated it for safety, quality, or efficacy. This article explains how the two relate and where they differ.

What is clomiphene (Clomid) and what is enclomiphene?

Clomiphene citrate is a nonsteroidal SERM of the triphenylethylene group. According to the FDA-approved Clomid label, it is “a mixture of two geometric isomers [cis (zuclomiphene) and trans (enclomiphene)] containing between 30% and 50% of the cis-isomer.” Pharmacology references and a human pharmacokinetic study describe the typical split as roughly 62% enclomiphene and 38% zuclomiphene; the precise 62/38 figure traces to those sources, not to the FDA label itself.

Both isomers act on estrogen receptors, but they behave differently. Enclomiphene is the more antiestrogenic isomer that drives the rise in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) and, in turn, endogenous testosterone. Zuclomiphene is the more estrogenic, long-acting isomer that accumulates with repeated dosing. That difference is the spine of the comparison.

How do the two isomers behave in the body?

Clomiphene works as a SERM by binding estrogen receptors in the hypothalamus, producing anti-estrogenic feedback that increases gonadotropins (LH and FSH), as summarized in a StatPearls clinical pharmacology review. Because Clomid contains both isomers, its effects reflect a blend of a short-acting antiestrogen and a long-acting estrogen.

In a study of 12 healthy men taking 50 mg of clomiphene daily for 30 days, zuclomiphene built up to a peak of about 32.48 ng/mL by day 30, while enclomiphene peaked far lower (about 10.47 ng/mL) and cleared quickly. Zuclomiphene remained detectable in urine for 121 to more than 261 days after the course, with one subject still testing positive roughly eight months later. The same study reported isomer half-lives of about 5 hours for enclomiphene versus about 24 hours for zuclomiphene. The FDA Clomid label independently notes that “detectable levels of zuclomiphene persisted for longer than a month.”

For context, in that 12-man study, whole clomiphene at 50 mg/day for 30 days was associated with average increases of roughly +146% in testosterone, +177% in LH, and +170% in FSH versus baseline, with values returning to baseline about three to four weeks after stopping. Those figures describe whole clomiphene in healthy volunteers, not isolated enclomiphene and not Revive patient outcomes.

Enclomiphene vs clomiphene: side-by-side

Feature	Clomiphene (Clomid)	Enclomiphene
Composition	Mixture of enclomiphene + zuclomiphene (label: 30-50% cis)	The isolated trans-isomer
Estrogen activity	Blend of antiestrogenic + estrogenic isomers	More purely antiestrogenic
Persistence	Contains zuclomiphene, which can persist >1 month	Short-acting (half-life ~5 h in one study)
FDA approval	Approved only for ovulatory dysfunction in women	Not FDA-approved for any use
Use in men	Off-label	Off-label; compounded

The simplest way to hold the distinction in mind: enclomiphene is the antiestrogenic, short-acting half of clomiphene, while zuclomiphene is the estrogenic half that lingers. For more background, see our overviews of what enclomiphene is and enclomiphene side effects.

What does the research say about enclomiphene in men?

Enclomiphene specifically has been studied in randomized phase II research in men with secondary hypogonadism. In a 2013 pharmacodynamic and pharmacokinetic study of 48 men (44 completed per protocol) treated for six weeks with enclomiphene citrate at 6.25, 12.5, or 25 mg daily versus transdermal testosterone, enclomiphene raised total testosterone comparably to the testosterone arm and increased LH. In a separate randomized phase II trial comparing enclomiphene citrate with 1% topical testosterone gel, enclomiphene increased serum testosterone, LH, and FSH while conserving sperm counts; exogenous testosterone, by contrast, tends to suppress spermatogenesis. This sperm-preservation observation is the main reason enclomiphene draws off-label interest among men who wish to maintain fertility.

These are research outcomes in defined study populations over short durations. They are not guarantees, and individual results vary and are provider-determined. For a deeper comparison of approaches, see enclomiphene vs TRT and does enclomiphene work.

How does enclomiphene compare with testosterone therapy?

Testosterone is a DEA Schedule III controlled substance under the Anabolic Steroids Control Act of 1990. FDA-approved testosterone products require a valid prescription, a diagnosis (symptoms plus two low early-morning testosterone tests), and ongoing monitoring such as hemoglobin/hematocrit, PSA, and blood pressure. In February 2025, the FDA issued class-wide labeling changes adding a blood-pressure warning to testosterone products following the TRAVERSE and ambulatory blood-pressure monitoring studies.

SERMs such as clomiphene and enclomiphene are not controlled substances, which is a genuine point of difference. However, both appear in Section S4 (Hormone and Metabolic Modulators) of the WADA Prohibited List and on the U.S. Department of Defense Prohibited Dietary Supplement Ingredients List, and it is illegal to sell either as a dietary-supplement ingredient, per DoD Operation Supplement Safety guidance. Athletes subject to testing and service members should weigh this carefully. To learn how therapy access works generally, see how it works.

What is the regulatory status of each?

Clomid (clomiphene citrate) is FDA-approved only for ovulation induction in women desiring pregnancy; it is not approved to treat any condition in men. Branded enclomiphene (Androxal, Repros Therapeutics) was never approved: the FDA issued a Complete Response Letter in 2015 for secondary hypogonadism, the EMA recommended refusal of marketing authorization in January 2018, and development was subsequently discontinued.

Enclomiphene today is dispensed as a compounded preparation. The FDA Pharmacy Compounding Advisory Committee voted on June 8, 2022, not to add enclomiphene citrate to the final 503A Bulks List, and the substance currently sits in 503A Category 1 (“bulk drug substances under evaluation”) per the FDA list updated May 14, 2026. Category 1 is not approval and is not the final Bulks List. Compounded enclomiphene is not FDA-approved, and the FDA has not evaluated it for safety, quality, or efficacy.

Frequently asked questions

Is enclomiphene the same as Clomid?

No. Clomid is clomiphene citrate, a mixture of two isomers. Enclomiphene is only the trans-isomer purified from that mixture. Clomid is FDA-approved for ovulatory dysfunction in women desiring pregnancy; enclomiphene is not FDA-approved for any use and is dispensed compounded, which the FDA has not evaluated for safety, quality, or efficacy.

Why is enclomiphene considered the “active” isomer for raising testosterone?

Enclomiphene is the more antiestrogenic isomer, and in a 2013 phase II pharmacodynamic and pharmacokinetic study of 48 men with secondary hypogonadism it raised testosterone and increased LH. Zuclomiphene, the other isomer, is more estrogenic and longer-lasting. Use in men is off-label, and individual results vary and are provider-determined.

Is Clomid FDA-approved for men?

No. Per the FDA-approved label, Clomid is indicated only for ovulatory dysfunction in women desiring pregnancy. Any use of clomiphene or enclomiphene in men is off-label.

How long does zuclomiphene stay in the body compared with enclomiphene?

In a study of 12 healthy men taking 50 mg of clomiphene daily for 30 days, zuclomiphene was detectable for 121 to more than 261 days, while enclomiphene cleared quickly (half-life about 5 hours versus about 24 hours for zuclomiphene). The FDA Clomid label also notes zuclomiphene persisting longer than a month.

Does enclomiphene preserve fertility better than testosterone therapy?

In a randomized phase II trial comparing enclomiphene with topical testosterone gel, enclomiphene conserved sperm counts while raising testosterone, whereas exogenous testosterone tends to suppress sperm production. This was an observed trial outcome, not a guarantee; results vary by individual and should be evaluated by a licensed provider.

Is enclomiphene a controlled substance?

No. SERMs such as clomiphene and enclomiphene are not controlled substances, unlike testosterone, which is DEA Schedule III. However, both clomiphene and enclomiphene are on the WADA Prohibited List (S4) and the DoD prohibited list and cannot be sold as dietary supplements.