Understand S-23 fertility claims by checking the population, formulation and measured outcome. Human exposure research does not establish a recovery deadline.
Do not use S-23 for contraception or rely on an online fertility-recovery deadline.
S-23 is a selective androgen receptor modulator, or SARM. FDA warns against using SARMs and identifies infertility among the serious concerns associated with this drug class. A research-product label does not establish human safety. FDA consumer guidance.
The 2009 paper combined S-23 with estradiol benzoate in male rats; the estrogen supported mating behavior. The fertility experiment used injections. A separate oral-absorption experiment did not test contraceptive effectiveness.
Two often-confused results describe different measurements:
Higher S-23 exposures did not simply produce stronger sperm suppression. Testicular sperm counts increased at higher exposures, despite suppressed circulating reproductive hormones.
Recovery was assessed in a separate animal experiment after treatment stopped. The reported return of fertility applies to those rats and that combination. It cannot validate a human recovery deadline or a post-cycle drug regimen. Original methods and results.
It is inaccurate to say S-23 has never been administered to people. A 2025 primary study investigated small oral exposures to help interpret possible contaminated-product findings in anti-doping work. Each administration regimen involved five male volunteers, with urine collected before exposure and afterward.
Researchers measured S-23 and its metabolites using liquid chromatography–mass spectrometry, an analytical technique for identifying and measuring chemicals. The reported outcomes concerned urine concentrations, metabolism and detection. They did not measure semen recovery, successful conception, or reliable pregnancy prevention.
These are human data, but they do not close the fertility-evidence gap. A detection window also does not tell someone when reproductive function has recovered. Alhalabi and colleagues, 2025.
Check what researchers measured, in whom, and under which conditions before interpreting a fertility claim.
If avoiding pregnancy, discuss an established contraceptive method with a healthcare professional and use it consistently. If trying to conceive, disclose S-23 and other drug or supplement exposure during a fertility assessment; do not wait for an online recovery countdown to expire. NICHD recommends evaluating both partners when conception is difficult. NICHD reproductive-health guidance.
For checking another research claim, use our human-evidence worksheet. This article reviews study interpretation; it does not supply a personal-use protocol or certify a commercial product.
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