S-23 is one of the most potent SARMs ever studied, and almost all of what’s known about it comes from rat research. This guide explains what S-23 is, what the studies found and where to buy it for laboratory research.
In this guide
What is S-23?
It’s a non-steroidal SARM from the University of Tennessee research group that also produced andarine (S4). It binds the androgen receptor with very high affinity and acted as a full agonist in rat muscle. Rat data puts its oral bioavailability near 96%, with a half-life of about 12 hours.
S-23 research findings
S-23 is best known from a 2009 study by Jones and colleagues on male hormonal contraception. Combined with estradiol benzoate, it suppressed sperm production in every male rat tested, and fertility returned within about 100 days of stopping. The same study found dose-dependent gains in lean mass and bone density and a drop in fat mass.
A separate study in postmenopausal female rats found it increased sexual motivation without growing uterine tissue. You can read the papers on PubMed.
S-23 safety notes
There are no human trials. In rats it strongly suppressed testosterone and sperm production, which is exactly what the contraception research was looking for. It isn’t approved by the FDA.
S-23 compared with other strong SARMs
Researchers comparing high-affinity SARMs often look at it alongside LGD-4033 and RAD-140. LGD-4033 and RAD-140 have some human data. S-23 has none.
Where to buy S-23
Sports Technology Labs sells liquid S-23 at 20 mg/mL in a 30 mL glass dropper bottle and S-23 powder in a 2 gram pouch. The current batch tested at 99.8% purity with MZ Biolabs.
Storing the liquid and powder forms
Liquids from Sports Technology Labs are dissolved in USP-grade PEG-400 and bottled in UV-resistant glass with a glass dropper fixed into the cap. Keep the bottle upright, tightly capped and out of direct sunlight. Room temperature is fine, and there’s no need to refrigerate. If a bottle gets cold in transit and looks cloudy, let it warm to room temperature and swirl it gently.
Powder ships in a resealable foil pouch. Measuring tools aren’t included, so you’ll need an analytical balance that reads to at least 1 mg. Most labs dissolve it in PEG-400, the same carrier we use for our liquids. Reseal the pouch straight after use and store it somewhere cool, dry and dark.
How to read the COA
Each product page lists the purity and the COA date. Purity is the share of the target compound found by HPLC. The date tells you when that batch was tested. Most listings also show the certificate and the chromatogram in the image gallery, and we’ll email the full document if you ask. A single tall peak at the expected retention time is what you want to see. Small extra peaks are impurities, and the purity figure accounts for them.
S-23 FAQ
Is S-23 the same as S23?
Yes. It’s written both ways.
Why is it considered so strong?
It binds the androgen receptor with high affinity and acted as a full agonist in rat muscle.
Has it been tested in people?
No. All published research is in animals.
Buy S-23 from Sports Technology Labs today. Orders over $149 ship free in the US.
Everything sold by Sports Technology Labs is for laboratory research only. It isn’t for human or veterinary use, isn’t a dietary supplement and hasn’t been approved by the FDA. Nothing in this article is medical advice.