At a glance
Effects
- Lean muscle growth: In animal studies, S-23 increased lean body mass (LBM) dose-dependently, with effects comparable to or exceeding testosterone in muscle preservation assays [4][5].
- Fat loss / recomposition: Preclinical data show dose-dependent reductions in fat mass alongside LBM gains; community users report a 'hard, dry' physique appearance with minimal water retention [5][6].
- Bone mineral density: S-23 increased bone mineral density (BMD) in animal models independently of dose, suggesting a bone-protective effect [4].
- Strength gains: High AR binding affinity and full agonist activity contribute to reported strength increases; users compare its potency to high-dose oral anabolics such as stanozolol or oxandrolone [6].
- HPG axis suppression: S-23 markedly suppresses LH, FSH, and endogenous testosterone — the same property that prompted research into it as a male contraceptive — leading to near-total shutdown of natural testosterone in many users [4][5].
Non-steroidal SARM (aryl-propionamide)
~11–12 hours (animal data; no human PK studies)
Oral (high bioavailability ~96% in preclinical models)
No human approval; banned by WADA & NCAA (S1.2)
Detectable via LC-MS/MS; metabolites found days–weeks post-dose
About S-23
Every point here is drawn from public medical and harm-reduction sources. A bracketed number after a claim — like [1]— is a reference: tap it to open the exact source it's based on (numbered list at the bottom). It is not a rating or score. Educational information, not medical advice.
Product specifics
- Est. delivery
- 3–7 business days · EU tracked
Product details as stated by the vendor (claims, not independently verified). Delivery is our standard EU estimate.
What it is
S-23 is a non-steroidal selective androgen receptor modulator (SARM) originally developed by GTX, Inc. as an investigational male hormonal contraceptive and lean-mass preservation agent [1][2]. It has never been approved for human use and is classified as a research chemical, used off-label in performance and bodybuilding contexts [3][7].
How it works
S-23 binds to androgen receptors (ARs) with exceptionally high affinity (Ki ≈ 1.7 nM), acting as a full agonist — meaning it activates ARs more completely than older, partial-agonist SARMs like S-4 (Andarine) [1][2]. This potent AR activation in muscle and bone drives anabolic signalling (protein synthesis, lean mass retention), while simultaneously suppressing the hypothalamic-pituitary-gonadal (HPG) axis via feedback inhibition, sharply reducing LH, FSH, and endogenous testosterone production [4][5]. Its halogenated aromatic ring structure gives it high oral bioavailability (~96% in preclinical models) and strong metabolic stability [2].
Risks & side effects
Most important: S-23 is among the most testosterone-suppressive SARMs known: it can cause near-complete shutdown of the HPG axis, severely reducing LH, FSH, and endogenous testosterone, which — without proper post-cycle therapy — may lead to prolonged hypogonadism, infertility, and psychological effects [4][5]. There are no controlled human safety data, and the FDA has flagged the entire SARM class for liver damage, heart attack, and stroke risk [7][8].
Common
- Severe testosterone suppression — dose-dependent reduction in LH, FSH, and endogenous T [4][5]
- Libido loss, fatigue, and mood flattening during and after cycle [6]
- Increased aggression / mood swings ('roid-rage'-like) reported by users [6][7]
- Insomnia and irritability [8]
- Acne, oily skin, and hair thinning (androgenic alopecia risk) [8][9]
- HDL cholesterol reduction; possible LDL/triglyceride elevation [8]
Serious
- Testicular atrophy and impaired spermatogenesis; reversible in animal models on cessation, but human data absent [4][5]
- Hepatotoxicity — ALT/AST elevations reported; the FDA links the SARM class to liver damage [7][9]
- Gynecomastia risk secondary to testosterone/estrogen ratio imbalance from suppression [7]
- Cardiovascular strain — elevated blood pressure, palpitations, and lipid-driven atherosclerotic risk [8][9]
- Virilization in women even at low doses (voice deepening, menstrual disruption, hirsutism) [6]
- Elevated hematocrit — increases blood viscosity and thrombotic risk [8]
Rare
- Stroke or heart attack — flagged as possible by the FDA for the SARM class based on post-market surveillance [7]
- Prolonged hypogonadism requiring clinical intervention if PCT is inadequate [6]
- Inadvertent ingestion via contaminated supplements — S-23 is increasingly detected in product adulteration cases [3]
Safety & harm reduction
- Women — virilization risk even at microdoses [6]
- Pregnant or breastfeeding individuals [7]
- Persons with pre-existing liver disease or elevated liver enzymes [7][9]
- Anyone with active cardiovascular disease, hypertension, or high baseline hematocrit [8][9]
- Adolescents / those who have not completed skeletal maturation [9]
- Tested athletes — prohibited year-round under WADA S1.2 [3][5]
- Pre-cycle baseline: testosterone (total/free), LH, FSH, complete metabolic panel (CMP), full lipid panel, CBC [6]
- Mid-cycle: liver enzymes (ALT/AST), blood pressure, haematocrit [8]
- Post-cycle (3–6 weeks after cessation): repeat all hormones, lipids, and CMP; continue monitoring until baseline values return [6]
- Other SARMs or androgenic compounds — additive HPG-axis suppression and organ stress; avoid stacking [5][9]
- Hepatotoxic agents (alcohol, acetaminophen at high doses, other oral hepatotoxins) — additive liver risk [7][9]
- Hormone therapy (TRT, HRT) — unpredictable disruption of HPG axis [5]
- Lipid-affecting drugs (statins, fibrates) — S-23 itself impairs lipid profile; compounding effects are unstudied [8]
- Post-Cycle Therapy (PCT) is considered essential by the harm-reduction community due to the severity of testosterone suppression; SERMs such as clomiphene or tamoxifen are commonly used [6][8]
- Cycle length reported to be capped at 6–8 weeks to limit cumulative suppression; re-use only after laboratory confirmation of hormonal baseline recovery [6]
- Split daily dose into two equal administrations (AM/PM) to maintain stable plasma levels given the ~12-hour half-life [5][6]
- Estrogen monitoring is prudent: testosterone suppression can shift the androgen-to-estrogen ratio and increase gynecomastia risk [7]
Dosage context
No controlled human dosing studies exist — all figures below are community-reported only and must not be treated as medical guidance [3][5]. Commonly reported adult male practice: 10–20 mg/day split into two doses (e.g. 10 mg AM / 10 mg PM), for cycles of 6–8 weeks maximum [6]. Given the profound HPG-axis suppression, many harm-reduction sources suggest starting at the lower end (≤10 mg/day) and treating any cycle as requiring full PCT planning in advance [6][8]. Sources are thin and individual response is highly variable; no validated safe dose for humans exists.
Sources
- 1.Wikipedia — S-23 (drug)
- 2.MedChemExpress — S-23 Product & References
- 3.Wiley / Biomedical Chromatography — S-23 Urinary Metabolite Profile (2025)
- 4.SelfDecode Drugs — S23 Review (Ritter PharmD, Yazdi MD)
- 5.ResearchGate — S-23 Body Composition / Preclinical Data
- 6.Swolverine — S-23 Guide (Harm-Reduction Focus)
- 7.WebMD — S-23 Fast Facts
- 8.MorePlatesMoreDates — S23 Preclinical Overview
- 9.RCPeptides — S-23 Risk & Monitoring Summary (link unavailable)
- 10.FitScience — S23 Dosage, Half-Life, Side Effects & PCT
This information is provided for educational and harm-reduction purposes only. It is not medical advice. These substances can carry serious health risks; effects and safe use vary by individual. Consult a qualified healthcare professional before use. Legal status varies by country — it is your responsibility to know your local law. We do not encourage misuse.
Other options for S-23· 3 offers
Same compound from different labs/brands and pack sizes. Tap a row to switch brand — the price and buy button update instantly.
This compound comes in different forms (e.g. injectable vs oral vs topical). Cost per mg is only comparable within the same form.
| Brand | Form | Strength | Pack | Price | Per mg |
|---|---|---|---|---|---|
Generic | blister-pack | 10 mg/tab | 30 tab | 79,90 € | €0.266/mg |
GenericSelected | bottle | 50 mg/ml | 50 ml | 104,99 € | €0.042/mg |
Generic | oral-liquid | 50 mg/ml | 100 ml | 219,99 € | €0.044/mg |