Other Name(s): C18H13ClF4N2O3
Half Life: 18-24 hours, depending on individual
What is S23?
S23 is an orally bioavailable, nonsteroidal selective androgen receptor modulator (SARM) that has been proven to increase lean muscle and bone tissue while being tissue selective (unlike traditional steroids).
Studies and user reports suggest that S23 is the closest SARM to steroids, with a few key differences, such as decreased prostate size. Other user reports suggest that S23 is a much more powerful version of S4 Andarine) and the benefits of this SARM falls in the category of hardening muscle and creating a grainier aesthetic look.
Read on for a comprehensive review of everything you need to know about S23, including benefits, side effects, studies and results for increasing muscle mass and preserving gains.
S23 is currently being investigated by GTX, a pharmaceutical company that primarily develops hormonal drugs, including a number of other SARMs. Interestingly, S23 is being investigated as a potential male hormonal contraceptive as studies have shown dose-dependent suppression of sperm. 
How it works
As a member of the SARM category, S23 works to selectively target and produce anabolic results in muscle and bone tissue without some of the limitations and side effects of traditional steroids.
Benefits of S23
Many users and studies suggest that S23 is one of the most powerful SARMs on the market. We’ve listed the primary benefits you can expect when taking S23.
- S23 helps build lean muscle mass. The number one benefit of supplementing with S23 is its ability to increase lean body mass. The second core benefit is the proven ability to retain gains after completing a cycle, as shown in this study. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2630904/
- S23 can increase strength and stamina during high-intensity workouts. Want to work out longer, harder and get better results every time you hit the gym? Users report enhanced speed, stamina, and endurance during workouts when supplementing with S23. Additionally, thanks to its ability to increase lean muscle tissue and decrease fat, high-intensity workouts and interval training can be optimized every time. One thing to note, however, is a user-reported side effect of increased anger whilst supplementing with S23, which may be a factor in increased effort and intensity during a workout.
- S23 can increase fat loss .S23 is to increase fat loss and fat oxidization. The study showed that rats treated with S23 increased lean muscle mass and bone mineral density whilst simultaneously reducing fat loss percentage. Interestingly, this study shows that there is an inverse relationship between a higher dose of S23 and a decrease in body fat. This suggests that a higher dose of S23 results increased fat loss.
- S23 shows minimal water retention. Water retention isn’t all bad. Some users suggest that water retention and bloating experienced during bulking periods can help to lubricate and protect joints. But S23 has been shown to offer minimal (if any) water retention and bloating, which means that all gains during a cycle will be retained. The fact that S23 does not cause water retention makes it ideal for cutting periods.
- S23 can help develop a harder and grainier muscle aesthetic. Some users suggest using S23 to maintain and build lean muscle whilst cutting, as this SARM tends to develop dry, grainy-looking muscles that are otherwise unattainable without traditional steroids. Many bodybuilders find S23 ideal in the lead up to competitions in order to create the level of muscular detail that wins competitions.
Below are some of the typical side effects associated with taking the S23 SARM, each one in further detail…
- Testosterone shutdown. S23 is the most potent SARM to date and has been suggested to be as close to traditional steroids as possible. With this in mind, the side effects of S23 are dissimilar to other SARMs, in that it does actually show an effect on testosterone levels in the form of complete down. Users report minimizing or even eliminating this side effect by supporting their supplementation of S23 with Testosterone Replacement Therapy (TRT).These side effects were completely reversed in studies upon cessation of S23 and the completion of a full PCT.
- Increased aggression. Some users report increased aggression when supplementing with S23, which could be a deterrent to some users with known anger issues.
- Testicle and prostate shrinkage. Temporary shrinkage of the testicles has been noted by some users, and the primary study on S23 shows prostate shrinkage. However, it’s worth noting that even with its similarities to steroids, the decrease in prostate size is unusual as steroids normally cause an increase, which can cause issues. Users note that testicle shrinkage was reversible once supplementation was stopped.
- Darker urine. Some users report darker-than-usual urine while cycling S23. This stopped when the cycle was complete.
Studies on rats suggest that the human equivalent would be between 0.5mg-50mg. This makes it slightly difficult to gauge the best dosage, although as results are dose-dependent, it will depend on the look each individual is aiming to achieve and their own body makes up.
User reports suggest that 20mg-30mg split into three doses throughout the day provides the best results. This would look like 3 doses of 10mg spread throughout the day.
Current research indicates that it is tolerated for use up to 8 weeks, with users suggesting incorporating it into the last 8 weeks of a 12-week cycle.
As a contraceptive, studies suggest a dosage of 50mg may be effective, but as it is still in testing stages, we do not advise using S23 as a male contraceptive.
20mg-30mg per day
Post Cycle Therapy (PCT)
Post Cycle Therapy (PCT) is required when taking SARMS to help preserve muscle gains, prevent fat accumulation, maintain mood and motivation, and retain strength in muscles. Cycling also helps to allow hormone levels to return to their natural state in order to prevent unwanted dependency.
Typically, a PCT will last the same duration as supplementation. So if a user supplemented with a hormone for 12 weeks, a PCT of 12 weeks would also be required to bring their hormones back to baseline.
But do I need a PCT when taking SARMs?
As a general rule, SARMs do not disrupt hormone levels in the body making a traditional PCT unnecessary. However, due to the testosterone shutdown noted by users taking S23, a full PCT is recommended.
Many users recommend adding S23 to the end of a cycle to help reduce body fat, increase lean muscle and create a dry, grainier appearance.
For this reason, we suggest adding S23 into the final 8 weeks of a 12-week cycle.
Many users report stacking RAD140 (Testolone) with LGD4033 (Ligandrol) to provide a powerhouse for building lean muscle and burning fat.
Find out more about RAD140 (Testolone), MK677 Nutrabol and MK2866 (Ostarine).
- S23: 20-30mg;
- RAD140 (Testolone): 20-30mg;
- LGD4033 (Ligandrol): 10mg.
Looking for the ultimate SARM stack? KONG provides a well-rounded selection of SARMs chosen to work synergistically.
Take the hassle (and cost) out of purchasing your SARMs separately – KONG contains RAD140, MK677, MK2866 as well as LGD4033 and GW501516.
I’m trying it (S23) out right now @10mg/day stacked with 5mg of RAD140 and 5mg of LGD4033 and so far it has been awesome.
Where to buy S23 Online
As with all SARMs, it’s important to purchase high-quality compounds for reputable sources. Powersupps UK offers a product called Lucky SARMs, which contains a high dosage of S23 in every tablet.
You can read more about it below:
From studies and user reviews, S23 is an interesting SARM with a lot of promise to develop big gains, help cut body fat, and create beautifully textured muscle during a cycle.
As the most potent SARM on the market, it does have its side effects that need to be considered when choosing the best supplement for your needs. The great news is that these side effects can be reversed while maintaining lean muscle gains after the cycle is complete, making it a promising addition to any training plan.
The only obvious concern with S23 is the testosterone suppression and lack of clinical human studies that have been performed in the scientific community. However, anecdotal testimonials from the bodybuilding communities sound promising when this supplement is used correctly.
If you’re looking for increased lean muscle, increased fat loss, and more defined muscle texture, S23 is a great choice for your next cycle.
Clinical trials have not been performed, and S23 is not FDA approved for human use. However, existing studies and user-reported reviews are promising, and side effects look to be minimal and reversible.
Many users report seeing results after the fourth week of their 8-12 week cycle.
Most user-reported reviews suggest taking S23 for 8-12 weeks before taking a full PCT.
We do not recommend that women take S23 at this time. For women interested in SARMs, we suggest the Athena https://powersupps.co.uk/product/athena/ stack, which has been specifically formulated for women looking to create lean, defined muscles and cut body fat.
The suggested dosage is 20-30mg per day, although trialing different doses to find your sweet spot is recommended.
Absolutely. Due to the shutdown element of S23 (which is unlike any other SARM) a full PCT should be performed to revert testosterone levels back to their original levels.
Yes, S23 is legal to purchase from a number of research companies for research purposes. It is not yet sold for human consumption.
No, S23 is not a steroid, but it is considered the most potent SARM and the closest to a steroid on the market.
Jones, Amanda et al. “Preclinical Characterization of a (S)-N-(4-Cyano-3-Trifluoromethyl-Phenyl)-3-(3-Fluoro, 4-Chlorophenoxy)-2-Hydroxy-2-Methyl-Propanamide: A Selective Androgen Receptor Modulator for Hormonal Male Contraception.” Endocrinology 150.1 (2009): 385–395. PMC. Web. 23 Apr. 2018. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2630904/