Enclomiphene Citrate Month-by-Month: What to Expect in the First 3 Months

Print or save as PDFOpens the printable question sheet and your print dialog. No sign-up.

Where a month-by-month picture actually comes from

The controlled studies of enclomiphene report results at fixed points: after the first dose and at six weeks in a 48-man phase 2 dose-finding study [5], at 12 weeks in two placebo-controlled phase 3 trials [1][2], and at 16 weeks in two phase 3 trials against a testosterone gel [6]. A smaller phase 2 study checked semen at three months [7]. Any month-by-month account is assembled by stitching those time points together, not read off a published timeline.

How the drug behaves during those weeks

Enclomiphene is an oral selective estrogen receptor modulator (SERM). It blocks estrogen receptors in the pituitary, and estrogen normally restrains the pituitary-testis axis, so blocking it releases more luteinizing hormone (LH) and follicle-stimulating hormone (FSH); those two hormones tell the testes to make testosterone and keep making sperm. It is studied in secondary (hypogonadotropic) hypogonadism, where the testes are healthy but under-stimulated, and would not be expected to work in primary testicular failure [3].

It is absorbed quickly, peaking about 2 to 3 hours after a dose, with a half-life of roughly 10 hours; the main metabolite is 4-hydroxy enclomiphene and excretion is mainly in feces [3]. It is related to clomiphene but is not the same drug: clomiphene citrate is a mixture of enclomiphene (trans) and zuclomiphene (cis), and zuclomiphene is the more estrogenic of the pair [3][8].

Weeks 1 to 6: the earliest measured points

The first controlled measurements come from a randomized, single-blind, two-centre phase 2 study. In it, 48 men with secondary hypogonadism took 6.25, 12.5 or 25 mg once daily or used testosterone gel, and testosterone and LH were measured hourly for 24 hours after the first dose and again after six weeks. Total testosterone and LH rose with enclomiphene [5]. The phase 3 protocols used 12.5 mg daily, escalating to 25 mg daily at week 6 if morning testosterone was still below 300 ng/dL [1].

What the trials do describe is early tolerability: in ZA-302, headache was reported by 7 of 112 men on 12.5 mg versus 1 of 47 on placebo, and nausea by 4 of 112 versus 3 of 47 [2]. In the phase 3 data, the most frequent side effects were headache, hot flushes, nausea and muscle spasm, and the reasons men stopped included blurred vision, muscle spasm, headache and aggression [2].

Weeks 6 to 12: the phase 3 numbers

ZA-301 enrolled 151 men aged 18 to 60 with morning testosterone under 300 ng/dL and normal sperm concentration; they were randomized to enclomiphene 12.5 or 25 mg or placebo for 12 weeks. Pooled across doses, 78.8% (95% CI 70.3 to 85.3, n=113) reached an average 24-hour testosterone of 300 to 1040 ng/dL. The pre-set success bar was a lower confidence limit of at least 67%, and FDA did not require a placebo comparison for this endpoint [1].

ZA-302 used the same design in 181 men (112 on 12.5 mg, 22 on 25 mg, 47 on placebo); 81.3% (95% CI 73.9 to 87.0, n=134) reached the normal range [2]. Both sets of results are posted on ClinicalTrials.gov rather than in a journal paper.

For a broader estimate, a 2025 meta-analysis of randomized trials of SERMs (clomiphene and enclomiphene pooled) in men with functional hypogonadism found total testosterone higher than placebo by a mean 273.76 ng/dL (95% CI 191.87 to 355.66), with high heterogeneity (I2 89%), and no significant difference in testosterone against testosterone gel. LH rose by 4.66 IU/L and FSH by 4.59 IU/L versus placebo [9].

Sperm counts at the three-month mark

Sperm results at three months differ by study. In a phase 2b study of 12 men who had been using topical testosterone, sperm counts rose in 7 of 7 men on enclomiphene at three months, while the gel did not raise counts above 20 million/mL in any of 5 men at that point [7]. In the phase 3 trials, a fall in sperm concentration of 50% or more occurred in 14.2% of men on enclomiphene versus 2.6% on placebo in ZA-301, and 14.2% versus 4.3% in ZA-302 [1][2]. By 16 weeks in the two gel-comparison trials, sperm concentration stayed in the normal range on enclomiphene while there was a marked reduction in spermatogenesis on testosterone gel; the published abstract gives no numbers [6]. A randomized phase 2 trial reported that sperm counts were conserved [10].

Will you feel different? What was and was not measured

The phase 3 trials measured testosterone, LH, FSH and sperm counts, not symptom or quality-of-life improvement. FDA's 2018 guidance on secondary hypogonadism, as described by FDA in 2022, says it is unclear whether raising testosterone in this population produces clinical benefit, that trials should show meaningful improvement in at least one symptom or sign, and that semen-parameter changes alone are not enough [3]. The EMA reached a similar view in 2018: the studies showed higher testosterone but did not examine whether symptoms such as bone strength, weight gain, impotence or libido improved [4].

One retrospective chart review of 66 men who took clomiphene and later enclomiphene found a median testosterone rise of 166 ng/dL with enclomiphene versus 98 ng/dL with clomiphene (P=0.20), an estradiol change of -5.92 versus +17.50 pg/mL (P=0.001), and fewer side effects on enclomiphene (odds ratio 0.18, 95% CI 0.07 to 0.44). It was not randomized [11].

Side effects and safety signals to watch

In 2022 FDA listed the safety concerns that came out of published trials, adverse event reports and the EMA review: cardiac and thromboembolic events (including pulmonary embolism and deep vein thrombosis in a safety study), raised estradiol, raised PSA, raised hematocrit, and no long-term safety data. The EMA noted a slightly higher rate of cardiac and thromboembolic events than with testosterone, and cataracts in nonclinical studies, which were not conclusively linked in people; the EMA wanted ocular monitoring [3].

On vision, the Clomid label covers clomiphene citrate (the mixture) in women treated for ovulatory dysfunction, not enclomiphene, so it cannot establish the risk for enclomiphene. The label says blurring, spots or flashes may occur and are usually reversible, although cases of prolonged visual disturbance have been reported [12]. In the enclomiphene phase 3 data, blurred vision was among the reasons men stopped treatment [2].

Approval status and what it means for a three-month course

Enclomiphene is not FDA-approved. FDA's own advisory-committee presentation says no FDA-approved drug contains enclomiphene as an active ingredient [3]. The sponsor's application received a complete response letter in 2015; as FDA summarised it, the phase 3 design was not adequate to show clinical benefit and there were concerns about entry criteria, titration and bioanalytical method validation [3]. The EMA's committee adopted a negative opinion on EnCyzix on 25 January 2018, based on 4 main studies in 588 patients, citing among its reasons a risk of venous thromboembolism [4].

A 2026 British Society of Sexual Medicine position statement notes that enclomiphene is not approved by the FDA or EMA, that its manufacturer discontinued development in 2021, and advises use only by experienced clinicians in specialist or research settings because long-term efficacy and safety data are lacking [8]. Because there is no approved product and no USP monograph, pharmacies cannot treat it as a routine compounded item: FDA lists enclomiphene citrate in Category 1, bulk drug substances under evaluation (list updated 14 May 2026), and says it does not intend to act against a compounder using a Category 1 substance if its guidance conditions are met, which is enforcement discretion rather than approval [13]. In 2022 FDA proposed not adding it to the allowed list, and its advisory committee voted 4 yes, 8 no [14]. Compounded enclomiphene has not been reviewed by FDA for safety, effectiveness or quality [15].

HealthRX.com offers enclomiphene by prescription.

What happens after three months

In the 12-man phase 2b study, total testosterone fell back to pre-treatment values one month after stopping enclomiphene [7].