Short answer: Clomiphene citrate (Clomid) is a mix of two mirror-image forms: zuclomiphene (cis) and enclomiphene (trans). The Clomid label says the cis form makes up 30% to 50% and lasts longer in the body. Enclomiphene is the trans form on its own. In phase 2 and phase 3 trials, enclomiphene raised testosterone, LH and FSH in men with secondary hypogonadism while keeping sperm counts in the normal range, unlike testosterone gel. Neither drug is FDA-approved for men: Clomid is labeled for ovulation problems in women, and enclomiphene has no approved US product. As of May 2026, FDA lists enclomiphene citrate in category 1 for compounding, meaning it is still under evaluation.
For men with low testosterone who want to keep their own production, or their fertility, clomiphene and enclomiphene come up quickly. They are often described as "the same drug" or as "the better half" of the same drug. Both are partly true. This article explains the chemistry, the trials, the labels and the current regulatory status in plain words, without dosing advice.
The Clomid label states that clomiphene citrate "is a mixture of two geometric isomers [cis (zuclomiphene) and trans (enclomiphene)] containing between 30% and 50% of the cis-isomer." The label also notes that in single-dose studies, "zuclomiphene (cis) has a longer half-life than enclomiphene (trans)," with zuclomiphene detectable for longer.
Why does that matter for men on daily clomiphene? Because the longer-lasting isomer builds up. A study of 15 men on clomiphene 25 mg daily for at least six weeks (median 25.9 months) found median serum levels of 2.2 ng/mL enclomiphene and 44.0 ng/mL zuclomiphene, a ratio of about 20 to 1 (Helo 2017). The authors argued this supports developing a pure isomer, because the two have different properties. The label says the isomers have "mixed estrogenic and antiestrogenic effects."
Both block estrogen's feedback at the brain. With less estrogen signal, the pituitary releases more LH and FSH, and the testes make more testosterone and keep producing sperm. That is the main difference from testosterone therapy, which lowers LH and FSH. See hCG on TRT for fertility for why that matters.
These trials were 16 weeks or shorter, and they measured hormone levels and sperm counts, not symptoms over years or pregnancy rates.
A 2025 systematic review and meta-analysis pooled randomized trials of clomiphene and enclomiphene in men with functional hypogonadism (Hohl 2025). Compared with placebo, the drugs raised total testosterone by a mean of about 274 ng/dL, LH by 4.7 IU/L and FSH by 4.6 IU/L. Testosterone levels were not significantly different from testosterone gel, while LH and FSH were higher. The analysis showed high variation between studies.
The Endocrine Society's 2018 guideline was more cautious about clomiphene, noting that "neither its efficacy nor its safety has been demonstrated in randomized trials." The trial base has grown since, but long-term outcome data are still thin.
The Clomid label is written for women, but it includes one line about men: "There are no adequate or well-controlled studies that demonstrate the effectiveness of clomiphene citrate in the treatment of male infertility. In addition, testicular tumors and gynecomastia have been reported in males using clomiphene." The label adds that the cause-and-effect relationship between the testicular tumor reports and clomiphene "is not known." Clomid's other label warnings, including visual symptoms, are written for its approved use in women.
Enclomiphene has no US label to quote, because no enclomiphene product is approved.
| Clomiphene citrate | Enclomiphene | |
|---|---|---|
| What it is | Mix of cis (zuclomiphene, 30-50%) and trans (enclomiphene) | Trans isomer only |
| FDA-approved product | Yes (Clomid), for ovulatory dysfunction in women | None in the US |
| Use in men | Off-label | Not approved; compounded or investigational |
| Randomized trials in men | Yes, pooled in 2025 meta-analysis | Phase 2 and two phase 3 trials (16 weeks) |
| Build-up with daily use | Zuclomiphene accumulates (about 20:1 in one study) | No zuclomiphene component |
| FDA compounding status | Approved drug component | Category 1 (under evaluation), as of May 14, 2026 |
FDA's list of bulk drug substances nominated for 503A compounding, updated May 14, 2026, places enclomiphene citrate in category 1. Category 1 means it was nominated with enough information for FDA to evaluate, and FDA does not intend to take action against pharmacies compounding it while the evaluation is ongoing, if the guidance conditions are met. It does not mean FDA has found it safe or effective. Clomiphene citrate is the active ingredient in an approved drug, so it can be compounded under the normal rules. Our compounding explainer covers how categories work.
For tested athletes: the WADA 2026 Prohibited List names clomifene under S4.2 (anti-estrogenic substances), a class that is listed as "including, but not limited to" the named drugs.
Dose Track handles daily oral schedules as well as injections, so you can log enclomiphene or clomiphene alongside any other medication and line up lab results against what you actually took.
Questions about the app? See the help center or join the Dose Track community.
Every number in this article comes from one of these sources, checked on October 22, 2026. This article is for education. It is not medical or legal advice, and nothing here is a dose recommendation.