Enclomiphene Citrate Microdosing Protocols: What the Evidence Actually Shows

Does any study define an enclomiphene microdosing protocol?

The trial record contains no regimen defined as microdosing, meaning a low starting dose with its own titration rules. What exists is a dose-finding study that ran 6.25 mg as one arm [2], and a phase 3 design that began at 12.5 mg and escalated on a lab trigger [3]. Neither is microdosing in the sense of starting below the studied range and staying there.

What doses were actually given?

6.25 mg

The 6.25 mg dose was used in a randomized, single-blind, two-center phase 2 study of 48 men with secondary hypogonadism, comparing enclomiphene 6.25, 12.5 and 25 mg daily against transdermal AndroGel for 6 weeks [2]. Enrolled men had morning total testosterone below 350 ng/dL and low-to-normal LH below 12 IU/L on at least two occasions [2]. Testosterone and LH rose with enclomiphene [2].

12.5 mg and 25 mg

These are the doses the phase 3 program used. The ZA-301 protocol gave 12.5 mg once daily, with up-titration to 25 mg at week 6 if morning testosterone was still below 300 ng/dL [3]. ZA-302 enrolled 112 men on 12.5 mg, 22 on 25 mg and 47 on placebo [5].

A 16-week comparison with testosterone gel

Two parallel randomized, double-blind, double-dummy, placebo-controlled trials (ZA-304 and ZA-305) compared two enclomiphene doses with AndroGel 1.62% for 16 weeks in overweight men aged 18 to 60 with secondary hypogonadism and morning testosterone of 300 ng/dL or lower. Total testosterone rose in every treatment group; LH and FSH rose with enclomiphene and fell with the gel; sperm concentration stayed in the normal range on enclomiphene while spermatogenesis fell markedly on testosterone gel [6].

What standard dosing actually achieved

Two placebo-controlled 12-week trials have posted results.

ZA-301 enrolled 151 overweight men aged 18 to 60 with acquired hypogonadotropic hypogonadism, morning testosterone below 300 ng/dL and normal sperm concentration. Pooled across the enclomiphene arms, 78.8% of 113 men reached an average 24-hour testosterone in the normal range of 300 to 1040 ng/dL (95% CI 70.3 to 85.3). The pre-set success bar was a lower confidence limit of at least 67%, and FDA did not require a placebo comparison for that endpoint. Sperm concentration fell by 50% or more in 14.2% of men on enclomiphene versus 2.6% on placebo [3].

ZA-302 used the same design with 181 men. Testosterone landed in the normal range in 81.3% of 134 men on enclomiphene (95% CI 73.9 to 87.0), and sperm concentration fell by half or more in 14.2% versus 4.3% on placebo. Headache was reported by 7 of 112 men on 12.5 mg and 1 of 47 on placebo; nausea by 4 of 112 and 3 of 47 [5].

The results of both trials are posted on ClinicalTrials.gov only. Neither was designed to test a starting dose below 12.5 mg.

Safety at the studied doses

Regulators flagged cardiac and thromboembolic events, including pulmonary embolism and deep vein thrombosis in a safety study, along with raised estradiol, raised PSA, raised hematocrit and the absence of long-term safety data [1]. The most frequent side effects reported with enclomiphene were headache, hot flushes, nausea and muscle spasm; the reasons men stopped included blurred vision, muscle spasm, headache and aggression [5].

Approval status

Enclomiphene is not approved. FDA's own advisory-committee materials state that no FDA-approved drug contains enclomiphene as an active ingredient [1]. The sponsor received a complete response letter in 2015, and EMA's committee adopted a negative opinion on EnCyzix on 25 January 2018 [1][4]. A 2026 British Society of Sexual Medicine position statement notes that the manufacturer discontinued development in 2021 and advises use only by experienced clinicians in specialist or research settings [7].

Where compounding stands

Enclomiphene has no approved product, no USP monograph and is not on FDA's final list of bulk substances that can be used in compounding. FDA's list, updated 14 May 2026, places enclomiphene citrate in Category 1, Bulk Drug Substances Under Evaluation. FDA says it does not intend to take action against a compounder using a Category 1 substance if the conditions in its guidance are met; that is an enforcement-discretion policy, not an approval and not a finding that the product is safe or effective [8].

At the 8 June 2022 meeting of FDA's Pharmacy Compounding Advisory Committee, FDA proposed that enclomiphene citrate not be added to the allowed bulk substances list. The vote was 4 yes and 8 no; members who voted no cited a lack of clinical efficacy evidence [9].

Enclomiphene is not on FDA's list of bulk substances that may present significant safety risks, and compounded enclomiphene products are not FDA-approved and have not been reviewed by FDA for safety, effectiveness or quality [10].

What the clomiphene label says, and why it is not an enclomiphene label

The Clomid label covers clomiphene citrate, the mixture of enclomiphene and zuclomiphene, not enclomiphene alone; by FDA's account the USP monograph gives enclomiphene content of clomiphene at 50 to 70 percent [1].

The label's indication is ovulatory dysfunction in women who want to become pregnant. It states that there are no adequate or well-controlled studies demonstrating effectiveness in male infertility, and that testicular tumors and gynecomastia have been reported in men taking clomiphene, with cause and effect not known [11]. Its visual-symptom and contraindication warnings apply to the mixture and have not been shown to hold for enclomiphene alone [11].

What the trials did not measure

The phase 3 comparison trials measured testosterone, LH, FSH and sperm concentration, not whether men felt better [6]. FDA's 2018 guidance on secondary hypogonadism, as the agency described it 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 [1]. EMA made the same point in refusing EnCyzix [4].