Many users think YK11 is the key to unlocking the body’s full potential and achieving fast muscle gains with few side effects. YK11 appears to be a super-SARM based on the reviews, while in reality, this drug is NOT a typical SARM. This article breaks down the science and reviews to give you a clear idea of what to expect from this SARM-steroid hybrid, with risks and side effects.
Note: By writing this post, we are not recommending this drug. Some of our readers requested that we commission a post on it, and we are simply providing information that is available in the scientific literature. Please discuss your medications with your doctor. Ostarine is specifically a drug that we at SelfHacked would recommend against.
What is YK11?
YK11 is a new synthetic steroid based on 5-α-dihydrotestosterone (DHT), a hormone naturally found in the human body. DHT is a stronger form of testosterone that targets androgen receptors in the prostate, sex organs, hair, and liver.
YK11 is gaining interest from bodybuilders due to its ability to quickly build muscle with minimal side effects, much like various SARMs. The structure of YK11 is unique. The YK molecule shares more in common with steroids than SARMs, although it’s often mistakenly placed in the same bucket as all other non-steroidal SARM [R].
YK11 may also enhance bone health. In a study on bone cells, YK11 increased the levels of bone-building proteins [R].
Some bodybuilders who have experimented with YK11 report great muscle gains and fat loss with minimal side effects. However, there are currently no animal or human studies of YK11 and its safety is unclear.
YK11, along with all steroids and SARMs, is banned in professional sports by the World Anti-Doping Agency [R].
Is YK11 a SARM?
Bodybuilders and researchers sometimes refer to YK11 as a SARM (selective androgen receptor modulator). This may be misleading as other drugs that are traditionally called SARMs differ from YK11.
YK11 is a steroid made by directly altering the chemical structure of DHT. In contrast, all other SARMs have a nonsteroidal structure. YK11 and SARMs work differently in the body and may have different side effects [R, R].
Cell studies do show that YK11 has a selective effect on androgen receptors. This means the SARM label does technically describe YK11 [R].
Because this class of drugs is so new, no established naming convention exists. Based on its activity and chemical structure, it may be more appropriate to call YK11 a synthetic steroid rather than a SARM.
How Does YK11 work?
The chemical structure of YK11 is similar to DHT and it binds to androgen receptors in a similar way. DHT is a naturally occurring hormone in the body, crucial for hair growth, prostate health, proper development in puberty.
Some bodybuilding resources state that YK11 is one of the strongest SARMs on the market. However, research revealed that YK11 only partially activates androgen receptors and prevents full activation. Such limited activation increases the activity of catabolic androgenic genes [R].
Importantly, YK11 is also a myostatin inhibitor. A recent cell study uncovered the basis of YK’s unique muscle-building mechanism: increasing follistatin levels. Follistatin is a naturally occurring protein in that suppresses myostatin, which otherwise prevents muscles from getting too large. In comparison, no other SARMs show myostatin inhibition [R].
YK11 may also increase bone growth by affecting a DHT-like pathway, according to other cellular studies. YK11 activates protein kinase B (PKB), which sends signals to increase the activity of bone-building cells [R].
Snapshot of YK11
- Increases muscle growth
- May boost fat-burning
- May increase bone strength
- Fewer side effects compared to steroids
- Steroidal structure (not a typical SARM)
- Testosterone suppression
- No human or animal studies
- Long-term risks unknown
Potential Uses of YK11
1) YK11 May Increase Muscle Size
YK11 may not be a SARM in the traditional sense, but it has a strong potential to enhance muscle growth.
YK11 boosts the growth of muscle cells by increasing follistatin levels, according to cell-based studies. Follistatin suppresses myostatin, a protein that normally stops excessive muscle growth. If the effects of follistatin are blocked (such as with anti-follistatin antibodies), myostatin inhibition doesn’t happen and YK11 loses its muscle-building effects [R].
YK11 has not been studied in animals or humans.
Anecdotal evidence from bodybuilders suggests it is effective at increasing muscle size. Users report lean muscle gains of up to 15 lbs and a decrease in body fat after a single cycle.
2) YK11 May Strengthen Bones
Sex hormones play an important role in maintaining healthy bones. YK11 may be able to bind to androgen receptors in bone tissues and increase bone strength, similar to steroids and SARMs.
YK11 increased levels of activated PKB (protein kinase B) in cells. Activated PKB sends signals to increase the growth of bone cells [R].
Strong bones and muscles are both critical for maintaining healthy bones and preventing fractures. Thanks to its muscle-building effects, YK11 may also support bone health, similar to SARMs. This would be especially relevant in older people who struggle with both muscle and bone frailty [R].
YK11 for Bodybuilding
New SARMs are always a hot bodybuilding topic, as their promise to increase muscle mass and burn fat with minimal side effects is appealing to many. YK11 has gained popularity due to its unique way of building muscle by increasing follistatin. There is also some debate on how to classify YK11, as it shares characteristics of both SARMs and steroids.
Positive reviews of YK11 report that it greatly increases muscle mass. The effects of are seen in as little as a week. Some users report no side effects at all or very mild testosterone suppression. However, these claims are clouded by the fact that people use different dosages, cycle lengths, or stack YK11 with other SARMs.
Some state that YK11 offers similar results to other SARMs. Many would prefer taking a SARM that is backed up with better research than YK11 if the results are similar. Users also report joint pain that has put them off from using YK11.
Bodybuilders have experimented with YK11 in both bulking and cutting. Allegedly, YK11 is useful in bulking because it builds a lot of lean muscle in a short amount of time. Others have taken advantage of YK11’s ability to burn fat and harden muscles by using it in cutting cycles.
There are reports of YK11 causing mild testosterone suppression. Most users agree that post-cycle therapy (PCT) is required.
According to some, YK11 might be ideal for those looking to put on a lot of muscle mass very quickly. All these claims remain purely anecdotal. Users must be cautious as there is very little information on YK11’s safety and long-term effects.
Anecdotal reports suggest the most common dosage is 10-15 mg/day. Users have also seen good effects at 5 mg, which is a recommended starting dose for new users. Some people report doses as high as 30 mg with no side effects. It is usually cycled for 4 to 8 weeks.
Female users report taking doses of 0.5-2 mg per day.
The half-life of YK11 has not been studied. A popular dosing strategy is to split each daily dose into two. By taking two doses a day, YK11 levels should remain more stable, although there is no clinical evidence to confirm this.
Most users take YK11 by mouth, but some people have used muscle injections.
Anecdotal evidence suggests that stacking YK11 with other SARMs can lead to superior results. Users report stacking YK11 with LGD-4033 or RAD140 and using a lower dose of YK11, typically 5-10 mg per day.
In Professional Sports
Anabolic agents, including all SARMs, are prohibited in professional sports by the World Anti-Doping Agency. No matter how YK11 is labeled — as a SARM or synthetic steroid — it is banned in competitions [R].
Despite being a fairly new drug, researchers have already developed a test that can measure YK11 metabolites. The doping test is currently in use and can detect YK11 metabolites for up to 2 days after use [R].
YK11 Side Effects
YK11 has only been studied in cells so far. There is no available clinical information on side effects. Not even animal studies have been carried out yet.
In a cell study, YK11 increased the levels of follistatin. High follistatin may increase the risk esophagus, stomach, skin, and prostate cancer. On the other hand, a human study suggests it may be beneficial for breast cancer [R, R, R, R, R].
The chemical structure of YK11 is very similar to other steroids that are toxic to the liver. YK11 may have toxic effects on the liver as well [R].
Theoretically, it may also affect the prostate, hair growth, vocal cords, and other organs.
Beyond the Science
Given the limited research, information from the bodybuilding community gives more insight into the potential real-world side effects of YK11.
Reported side effects include:
- Increased aggression
- Joint pain
- Low energy
- Mild testosterone suppression
- Hair loss
- Mild acne
YK11 is potentially toxic to the liver. However, some users reported doing blood tests during cycles of YK11 and initial results didn’t indicate abnormal markers of liver damage.
Mild testosterone suppression has been reported. To be on the safe side, almost all bodybuilding resources recommend post-cycle therapy (PCT) after a cycle of YK11. Common PCTs include Nolvadex (tamoxifen) and Clomid (clomifene).
Limitations and Caveats
The current research on YK11 is very limited. It has not been studied in animals or humans. All cellular studies on YK11 have been done by one group of researchers from Japan.
YK11’s safety and effectiveness can only be evaluated once more research is done.
Although S23 is available online as a research chemical, we advise against getting this drug given that its safety has not been confirmed in animal or humans.
YK11 is a new steroid-SARM hybrid. It has a steroid structure and the selectivity of non-steroidal SARMs. So far, only cell-based studies researched its effects and confirmed that it can build muscles via myostatin inhibition. YK11 may also strengthen the bones, potentially helping to prevent fractures.
Users report major gains for bulking and cutting cycles (4-8 weeks) that few other SARMs can par with. On the downside, YK11 may cause testosterone suppression, joint pain, and hair loss. Side effects are not too frequent and PCT is a must, according to most experienced users. Despite its promising effects, both animal and human studies are needed to determine its safety, the full range of effects, and strength.