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Research compound — not a dietary supplement
S-23 is a research compound, not a regulated dietary supplement. It is sold for research or off-label use. The evidence below is largely preclinical (animal and in-vitro) or early-stage, so no evidence score is assigned. This page is provided for transparency and education — it is not a recommendation to use. Consult a qualified healthcare provider, and be aware that purity, dosing, and legal status vary by jurisdiction.
What the evidence says
Most S-23 studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from mixed-quality studies published 2009–2025.
Based on 5 studies
Confidence
LowBy outcome
S-23 has an evidence score of 3/10 — emerging evidence based on 5 indexed studies. A high-potency oral SARM with ZERO human efficacy data — its only published animal work was as a reversible male contraceptive in rats, where it built muscle and bone while shutting down the HPTA and suppressing sperm to infertility. Sold grey-market for body composition, it is NOT an approved drug or a lawful supplement, products are frequently mislabeled, and it is banned by WADA. The human literature is limited to anti-doping detection, not benefit. This entry exists to inform, not to recommend. Representative study: PMID 18772237.
The commonly studied dose of S-23 is No legitimate or recommended dose — S-23 is an unapproved grey-market research chemical with no human efficacy or safety data and no quality control. We do NOT provide a dosing protocol. The only systematic dosing is in rats (sub-milligram per day, by the route used in those studies), and it was studied to SUPPRESS fertility. Human anti-doping studies have given microgram-to-low-milligram single oral doses purely to characterize detection, not to establish a safe or effective dose.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Ostarine (MK-2866 / Enobosarm)
Mostly mechanism / observationalA non-steroidal SARM (enobosarm / MK-2866) developed for muscle wasting and cancer cachexia. Real, large randomized trials show it genuinely adds lean body mass — but it has NEVER been approved: the pivotal cancer-cachexia program met its lean-mass endpoints while missing physical-function endpoints, so a durable functional benefit is unproven. Sold widely as a grey-market 'body-recomp' research chemical, it carries documented drug-induced liver injury, HDL/lipid suppression, and testosterone (HPTA) suppression, is banned by WADA, and the products sold online are frequently mislabelled. Real anabolic signal, unproven function, real harms.
Last reviewed June 2026 · evidence from 5 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
S-23 — high-potency selective androgen receptor modulator (SARM), studied preclinically as a male contraceptive candidate
A high-potency oral SARM with ZERO human efficacy data — its only published animal work was as a reversible male contraceptive in rats, where it built muscle and bone while shutting down the HPTA and suppressing sperm to infertility. Sold grey-market for body composition, it is NOT an approved drug or a lawful supplement, products are frequently mislabeled, and it is banned by WADA. The human literature is limited to anti-doping detection, not benefit. This entry exists to inform, not to recommend.
A high-potency, full-agonist SARM whose ONLY published efficacy evidence is a single rat study where it was developed as a reversible male contraceptive — building muscle and bone while suppressing LH/FSH and spermatogenesis to infertility. There is zero human efficacy or safety data; the human literature is limited to anti-doping detection. Products are an unregulated, frequently mislabeled grey market, and S-23 is WADA-banned. Very low score: an interesting androgen pharmacology story with no human evidence and a body-composition use that is inseparable from full reproductive shutdown.
S-23 ((2S)-N-(4-cyano-3-trifluoromethylphenyl)-3-(3-fluoro-4-chlorophenoxy)-2-hydroxy-2-methyl-propanamide) is an arylpropionamide-derived selective androgen receptor modulator (SARM) — the same chemical family as ostarine and andarine.
It is notable for being unusually potent: in the foundational preclinical work (Jones, Chen, Hwang, Miller, Dalton, Endocrinology 2009) it bound the androgen receptor with high affinity (Ki ≈ 1.7 nM) and acted as a FULL agonist, more like testosterone than the partial-agonist SARMs.
Critically, S-23 was developed and studied as a candidate hormonal MALE CONTRACEPTIVE, not a muscle-building drug.
In intact male rats it suppressed LH and FSH, shrank the prostate, increased levator ani (muscle) mass, raised bone mineral density and lean mass, and reduced fat — but combined with estradiol benzoate it suppressed spermatogenesis to the point of azoospermia and zero pregnancies in mating trials.
That infertility was fully reversible after withdrawal. This is the honest, load-bearing framing: the single piece of efficacy evidence for S-23 is an animal contraception study whose 'benefits' (lean mass, bone) are inseparable from full shutdown of the reproductive axis.
There has never been a human efficacy or safety trial of S-23. The only human data that exist are anti-doping detection studies — single-volunteer pharmacokinetic/metabolite work establishing how long S-23 stays detectable in urine — which characterize elimination, not benefit or safety.
S-23 has been on the World Anti-Doping Agency prohibited list for years and was responsible for multiple adverse analytical findings in athletes.
It is sold online as an unregulated 'research chemical' for body composition; analyses of SARM products marketed to consumers repeatedly find mislabeling — wrong compounds, wrong doses, undeclared prohibited analytes, or no active ingredient at all.
No SARM, including S-23, has ever met the safety and efficacy bar for approval by the FDA or EMA.
The score is very low: a high-potency androgen with promising rodent body-composition signals that are entirely entangled with reproductive shutdown, no human efficacy or safety data, a grey-market mislabeled supply chain, and a WADA ban.
S-23 binds the androgen receptor with high affinity (Ki ~1.7 nM in vitro) and acts as a full agonist — closer to testosterone than the partial-agonist SARMs. In castrated and intact male rats this drove tissue-selective anabolic effects (levator ani muscle, bone) at low doses. Demonstrated only in rat and in-vitro systems; no human pharmacodynamic data.
By agonizing the androgen receptor, S-23 suppressed pituitary LH and FSH in male rats, the same negative-feedback mechanism exploited deliberately to make it a male contraceptive. This suppression is why it shrank the prostate and, with estradiol, halted spermatogenesis. Established in rats; the magnitude and reversibility in humans are unstudied.
Combined with estradiol benzoate, S-23 suppressed sperm production to azoospermia in most treated male rats, producing zero pregnancies in mating trials — fully reversible after withdrawal. This is the central published 'efficacy' result for S-23, and it is a fertility-suppression effect, not a performance benefit. Rat-only; never tested in humans.
How S-23 works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Tap node to isolate • Pinch to zoom • Tap edge for research
No legitimate or recommended dose — S-23 is an unapproved grey-market research chemical with no human efficacy or safety data and no quality control. We do NOT provide a dosing protocol. The only systematic dosing is in rats (sub-milligram per day, by the route used in those studies), and it was studied to SUPPRESS fertility. Human anti-doping studies have given microgram-to-low-milligram single oral doses purely to characterize detection, not to establish a safe or effective dose.
Can be taken without food
| Form | Type |
|---|---|
| 💊None — unapproved grey-market research chemical | Recommended |
There is no legitimate pharmaceutical form. S-23 is a preclinical SARM studied as a male-contraceptive candidate; it is not a medicine or a dietary supplement, and it is banned in sport.
Minimum: 1 weeks
Optimal: 1 weeks
Cycling: Not required
Note: No approved or validated timing — the compound has never been tested for efficacy or safety in humans. This library does not endorse or schedule its use.
Dose-response data unavailable. The current published research for S-23 does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
There has never been a published human efficacy or safety trial of S-23. Every efficacy result here is from rats, and the only human studies are anti-doping detection work. Effects may not translate to people, and the human safety profile is unknown.
In male rats, S-23 dose-dependently increased lean mass and bone mineral density and reduced fat mass — the basis for its grey-market body-composition use. A genuine preclinical signal, but demonstrated only in rats and inseparable from reproductive-axis suppression.
The same dosing that built muscle and bone suppressed LH/FSH and, with estradiol, drove sperm counts to zero and infertility in male rats (reversible on withdrawal). S-23 was designed as a contraceptive — suppression of the reproductive axis is the expected effect, not an off-target one.
Sold online as an unregulated research chemical, S-23 products are frequently mislabeled (wrong compound, wrong dose, undeclared analytes, or nothing active). It is on the WADA prohibited list and has caused multiple adverse analytical findings in athletes, including via contaminated supplements.
Avoid — there are no human trials, no approved use, and no quality-controlled product. The rodent evidence (for a contraceptive) does not justify human self-experimentation.
Avoid — S-23 was designed to suppress sperm production; fertility effects in humans are unstudied.
Avoid — S-23 is WADA-banned and detectable in urine for weeks after a single dose.
Contraindicated — an androgen; entirely unstudied and unsafe in pregnancy.
Stacking androgens compounds HPTA suppression and androgenic load. No human interaction data exist; combined SARM/steroid use is unstudied and the toxicity of stacks is unknown.
There are no human drug-interaction data of any kind. As a hepatically metabolized androgen-receptor agonist, interactions cannot be predicted from the available animal and detection studies.
Tip: S-23 suppressed LH/FSH and spermatogenesis to infertility in rats. In humans the magnitude, time-course, and reversibility are unstudied — there is no way to make this safe.
Tip: As a full androgen-receptor agonist, S-23 is expected to exert androgenic effects; reviews note SARM abuse may raise cardiovascular risk. No human safety characterization exists.
Tip: Grey-market SARM products frequently contain the wrong compound, wrong dose, or undeclared analytes. Identity, purity, and sterility are not guaranteed.
Timing is flexible for S-23 — consistent daily use matters more than the time of day. There is no validated human dosing schedule because the compound has never been tested for efficacy or safety in humans.
S-23 should be used with caution — talk to a healthcare provider before taking it. The most commonly reported side effects are HPTA suppression / infertility (the intended contraceptive effect in animals), androgenic effects (prostate, lipids, virilization), harm from an unregulated, mislabeled product. Use caution if any of these apply to you: Not an approved medicine and not a regulated dietary supplement — unapproved grey-market research chemical; do not self-source; No human efficacy or safety data exists — every safety conclusion would be an extrapolation from rats; Anyone trying to conceive or preserve fertility — S-23 was developed to suppress spermatogenesis.
LGD-4033 (Ligandrol)
Mostly mechanism / observationalA nonsteroidal SARM with one small Phase-1 human RCT that did show dose-dependent lean-mass gain over 21 days — but at the cost of suppressed testosterone and HDL cholesterol even at low doses. It was never approved as a medicine, multiple case reports tie it to cholestatic liver injury, internet 'SARM' products are routinely mislabelled, and it is banned by the World Anti-Doping Agency. Sold only as an unregulated grey-market research chemical for body composition.