Enclomiphene

Yakka Strength Enclomiphene is a Yakka Strength listing of enclomiphene, supplied as 60 capsules per pack; the manufacturer does not state a strength per capsule on the label. It is supplied through the Muscle Market range for laboratory research only, is not for human consumption, and is sold to adults aged 18 and over. This page sets out what the published research on enclomiphene reports, what the label documents, how it differs from clomifene, how to read a batch certificate for a Yakka Strength product, and where it stands in UK law and in sport.

About Enclomiphene

Enclomiphene is the trans-isomer of clomifene, a selective oestrogen receptor modulator (SERM). Clomifene as prescribed is a mixture of two isomers; enclomiphene is the one that blocks oestrogen receptors in the hypothalamus and pituitary, which reduces negative feedback and raises secretion of LH and FSH. It was developed by Repros Therapeutics under the name Androxal for secondary hypogonadism in men. Chemically it is a small synthetic molecule, formula C26H28ClNO, molecular weight 406.0 as the free base, CAS 15690-57-0, PubChem CID 1548953, also indexed as enclomifene, trans-clomifene and RMI 16,289.

What the trials measured

A 2013 phase IIB study enrolled 12 men with secondary hypogonadism who had previously used topical testosterone, randomising them to oral enclomiphene citrate or testosterone gel. Both groups reached similar morning testosterone values at six months, but only the enclomiphene group showed higher LH and FSH, and sperm concentrations rose in every man in that group who was measured. Testosterone fell back to pre-treatment values one month after the study ended.

A 2014 randomised phase II trial in men with secondary hypogonadism reported that oral enclomiphene citrate raised serum testosterone into the normal range while sperm concentration was maintained, whereas topical testosterone lowered sperm counts. Two phase III trials published in 2016 reported the same pattern in obese hypogonadal men, with adverse events recorded in both arms.

Limits of the evidence and regulatory outcome

These studies were small or short, sponsored by the developer, and measured blood hormones and semen counts in men with a diagnosed condition rather than symptoms or long-term outcomes. Despite those data, the US application did not succeed: the FDA raised concerns about the trials and did not approve it. A European application did not lead to an authorisation either, so enclomiphene is not an authorised medicine in the UK, the EU or the US. Clomifene, its parent, is prescription-only in the UK. Nothing above is a claim about this product.

This listing

• Manufacturer: Yakka Strength
• Compound: Enclomiphene
• Form: Capsules
• Pack size: 60 capsules
• Strength: the manufacturer does not state the amount per capsule on the label, so we do not list one
• Batch certificate of analysis: shown where Yakka Strength supplies one for the batch we hold

Because no strength is stated, the total milligrams per pack cannot be worked out from the label, and cost per milligram cannot be compared with listings that do state one. Our guide to price per milligram explains the comparison for products where the figure is known.

Enclomiphene in the UK: buying, legal status and what to check

Searches such as "enclomiphene uk buy" and "enclomiphene uk legal" come down to two questions. Can an adult in the UK obtain enclomiphene lawfully, and how can a buyer tell a documented listing from an undocumented one.

Where enclomiphene sits in UK law

Enclomiphene is not a licensed medicine in the UK, holds no MHRA marketing authorisation, and is not an authorised food supplement. It is not a controlled drug. It is sold for laboratory research to adults aged 18 and over and is not for human consumption. Its position differs from its parent: clomifene is a prescription-only medicine, supplied only against a prescription for licensed uses, whereas enclomiphene on its own has no licence to be prescribed against. It is not a SARM either, although some sellers file it under that heading; it acts on oestrogen receptors, not androgen receptors. SERMs including clomifene are named under section S4 (hormone and metabolic modulators) of the WADA Prohibited List. Our research guide covers the wider legal picture.

What a documented UK listing shows

• A named manufacturer and a seller that can be identified and contacted in the UK.
• A milligram figure on the label, with enclomiphene specified as citrate or free base.
• A batch or lot number on the pack that can be matched to paperwork.
• A certificate of analysis for that batch, from a named laboratory, with a date.
• Research-use terms: sales restricted to adults, with no usage directions or outcome promises.
• Clear delivery and returns terms, published before purchase.

How this listing compares with that list

The manufacturer is named on the pack and the seller is FreeMuscle LTD, a UK company in Scunthorpe. UK orders go by free tracked delivery in plain packaging, orders placed before 2pm Monday to Friday are processed the same working day, EU delivery takes 3-7 working days, and unopened items can be returned within 30 days under our guarantee. Details are on the shipping page. The point this listing does not meet is strength: Yakka Strength prints no milligram figure, so any content figure can only come from a batch certificate where the manufacturer supplies one. A buyer who needs a stated strength and a certificate for every batch can compare Free Muscle enclomiphene, whose batches are assayed by Janoshik Analytical. A longer checklist is in how to choose a SARMs supplier in the UK.

Capsules compared with other forms

Searches for "enclomiphene tablets" arise because clomifene is dispensed as tablets, while research enclomiphene appears as capsules, tablets and occasionally liquids. The active molecule is identical across these formats; what varies is how precisely each unit is filled and how well the material is protected from moisture, air and light.

Capsules and tablets both start as a powder blend of the compound and an inactive filler. How close each unit is to its target depends on how evenly that blend was mixed before filling, and the only way to check is to assay several units from the same batch. A liquid holds the compound in solution, so its content is a concentration: accuracy depends on complete dissolution, on the measuring device and on the solvent not evaporating over time, which would slowly concentrate what is left. Dry solids generally degrade more slowly than solutions.

Enclomiphene is not a peptide, so the enzymatic breakdown in the gut that limits peptides given by mouth, discussed in do oral peptides work, does not apply to it. The published trials all gave enclomiphene citrate by mouth, which describes their design and says nothing about the performance of this product. The citrate point also matters for labels: a milligram figure for the salt contains less enclomiphene base than the same figure for the free base, so a strength is only comparable once the form is stated.

Enclomiphene compared with clomifene

"Enclomiphene vs clomiphene" is the most-searched comparison for this compound. Clomiphene is the US spelling; clomifene is the UK and international name. The answer is a matter of chemistry, evidence and regulation rather than one being better than the other.

Point	Enclomiphene	Clomifene
What it is	A single geometric isomer, (E) or trans	A mixture of the (E) isomer and the (Z) isomer, zuclomiphene
Behaviour of the isomers	The shorter-lived, oestrogen-blocking component	Also contains zuclomiphene, which is longer-lived and weakly oestrogenic
Human evidence	Phase II and phase III trials in men with secondary hypogonadism, sponsored by the developer	Decades of clinical use in female infertility; the 2019 detection study in healthy men
UK status	Not licensed; sold for research only	Prescription-only medicine
WADA	Section S4, prohibited at all times	Named in section S4, prohibited at all times

The two isomers share a formula and a mass but differ in shape, and that shape difference changes how they bind the oestrogen receptor and how long they stay in the body. The case for developing enclomiphene alone rested on removing the slow-clearing zuclomiphene from the mixture. The trials in men compared enclomiphene with testosterone gel, not with clomifene, so there is no head-to-head human trial of the two. Clomifene is not stocked by Free Muscle, because it is a prescription medicine; the only related collection we hold is the enclomiphene collection, which lists every brand of enclomiphene we carry. A longer treatment of the trials, with their adverse findings, is in our enclomiphene vs clomifene research guide.

Reading the certificate of analysis for this product

Yakka Strength is a third-party brand in the Muscle Market range, so the testing position differs from our own label. Every Free Muscle-brand batch is assayed by Janoshik Analytical, an independent laboratory, with the certificate sent on request by email. For Yakka Strength products we show a certificate of analysis only where the manufacturer supplies one for the specific batch we hold. A generic PDF with no batch number is not a batch certificate, and we do not present one as such. If you want to know whether a certificate is held for the current batch, ask through our contact page.

When a certificate is available, these are the lines to read:

• Identity. HPLC compares the retention time of the main peak with a reference standard; LC-MS adds the measured mass. For enclomiphene the isomer matters: enclomiphene and zuclomiphene have the same mass, so identity should be confirmed against an (E)-isomer reference. A report that says only "clomiphene" does not show which isomer is present.
• Purity. Usually an HPLC peak-area percentage. It describes the material tested, not how much is in each capsule, and zuclomiphene is the impurity most worth looking for.
• Assay or content. With no strength on this label, a measured amount per capsule is the only source of that number; check which form, salt or base, it refers to.
• Batch number and test date. The batch must match the pack; the date shows how old the analysis is relative to the stock.
• Issuing laboratory. A named laboratory can be asked to confirm that it issued the report.

For a third-party brand a missing field has a plain meaning. No identity line leaves the compound unconfirmed; purity without content leaves the strength unknown; no batch number means the document cannot be tied to the pack in hand. Our lab tests page and the article on how to read a certificate of analysis cover the general method, and our contact page is the route for requesting what we hold.

Detection, sport and testing

Enclomiphene is prohibited in sport at all times, in and out of competition. SERMs including clomifene are named under section S4 (hormone and metabolic modulators) of the WADA Prohibited List. Enclomiphene, as an isomer of clomifene, falls within that class. Strict liability applies, including to a mislabelled product.

The controlled detection study cited here concerns clomifene rather than isolated enclomiphene. In 2019 an anti-doping laboratory gave clomifene citrate to 12 healthy men aged 25 to 38 for a month. Serum testosterone, LH and FSH rose during treatment, drug concentrations varied widely between individuals, and zuclomiphene stayed detectable in urine from 121 to more than 261 days. That long window belongs to the zuclomiphene component. No verified study reports a urinary window for enclomiphene given alone, so for this product the accurate statement is: detectable, window not established.

Storage, stability and handling

Keep the pack sealed in its original container until it is needed, with the lid closed, in a cool, dry and dark place away from heaters, sunny windows, kitchens and bathrooms. Moisture is the main threat to capsules: gelatine and plant shells absorb water, soften and can stick together, and damp powder degrades faster. Warmth accelerates both processes, and each opening of the container lets in humid air.

No published stability study covers enclomiphene in capsule form that we are aware of, so the expiry or best-before date on the pack is the working limit, and the batch number should be recorded alongside the date the pack was opened. Do not decant capsules into unlabelled containers or mix them with another batch, because that breaks the link between the material and its certificate. Standard laboratory practice applies: gloves when handling opened capsules or loose powder, no food or drink in the working area, clear labelling, storage out of reach of children and pets, and disposal as chemical waste rather than in household bins or drains.

Glossary

• SERM: a compound whose effect at the oestrogen receptor depends on the tissue, acting as a blocker in some and an activator in others.
• Geometric isomers: molecules with the same atoms and formula but a different fixed arrangement around a double bond, labelled (E) and (Z).
• Zuclomiphene: the (Z) or cis isomer of clomifene, cleared from the body much more slowly than enclomiphene.
• Free base and citrate salt: the molecule alone, and the molecule paired with citric acid; the salt weighs more per unit of active compound.
• Secondary hypogonadism: a testosterone shortfall that originates in the brain's hormone signals, with the testes themselves intact.
• Gonadotrophins: LH (luteinising hormone) and FSH (follicle-stimulating hormone), released by the pituitary gland to regulate the testes.
• HPLC and LC-MS: liquid chromatography methods; HPLC separates a sample into peaks, and LC-MS adds a measurement of each molecule's mass.
• Certificate of analysis (COA): a dated test report tied by number to a single manufactured batch.
• Strict liability: the anti-doping rule that an athlete is responsible for any prohibited substance in their sample, regardless of intent.

Related

• All brands of Enclomiphene we stock, compared
• All Yakka Strength products
• Yakka Strength RAD-140 and Enclomiphene bundle
• Enclomiphene vs clomifene: what the trials report
• Batch testing and certificates of analysis
• Delivery and returns

This product is supplied for laboratory research use only. It has not been evaluated by the MHRA, EMA or FDA. It is not a medicine, not a food supplement and not for human consumption. Sold only to adults aged 18 and over. Nothing on this page is medical, dosing or usage advice, and descriptions of published studies are not claims about this product.

References

1. Kaminetsky J, et al. Oral enclomiphene citrate stimulates the endogenous production of testosterone and sperm counts in men with low testosterone: comparison with testosterone gel. J Sex Med. 2013;10(6):1628-35. PMID: 23530575.
2. Wiehle RD, et al. Enclomiphene citrate stimulates testosterone production while preventing oligospermia: a randomized phase II clinical trial comparing topical testosterone. Fertil Steril. 2014;102(3):720-7. PMID: 25044085.
3. Kim ED, et al. Oral enclomiphene citrate raises testosterone and preserves sperm counts in obese hypogonadal men, unlike topical testosterone: restoration instead of replacement. BJU Int. 2016;117(4):677-85. PMID: 26496621.
4. Miller GD, et al. Hypothalamic-Pituitary-Testicular Axis Effects and Urinary Detection Following Clomiphene Administration in Males. J Clin Endocrinol Metab. 2019;104(3):906-914. PMID: 30295816.