When it comes to building lean muscle mass with precision and speed, SARMs (Selective Androgen Receptor Modulators) like YK-11 and RAD-140 have carved out a dominant place in the performance enhancement world. But stacking these two together? That’s where the magic happens — and the muscle really starts to show.
YK-11, a unique myostatin inhibitor, and RAD-140, one of the most anabolic SARMs available, form a synergy that maximizes muscle growth without the bloating or water retention typically seen with traditional steroids. This stack is designed for athletes and bodybuilders looking to gain size, increase strength, and stay shredded — all at once.
Whether you're deep into your hypertrophy phase or looking for an edge during a recomp protocol, this article breaks down how the YK-11 and RAD-140 stack works, what the research says, and how to structure your cycle for results — with fewer side effects.
If you’re serious about pushing your physique forward, read on.
Need a supplement stack to match your goals? Check out the Swolverine Muscle Growth Stack to support your cycle with clinically dosed, performance-backed ingredients.
What Is YK-11?
YK-11 is one of the most unique compounds in the world of SARMs — although technically, it isn’t a true SARM. It’s often classified as a myostatin inhibitor with partial SARM activity, meaning it not only stimulates muscle growth by binding to androgen receptors but also limits the body’s natural ability to suppress growth through myostatin.
Myostatin is a protein that regulates muscle cell growth — in essence, it tells your body when to stop building muscle. YK-11 works by increasing follistatin, a natural antagonist to myostatin, allowing muscle cells to continue growing beyond what your body would normally permit.
This mechanism makes YK-11 incredibly powerful for:
→ Increasing muscle fiber size and density
→ Improving muscle differentiation at the cellular level
→ Gaining lean mass without significant water retention
→ Producing a hard, dry look when paired with a clean diet
YK-11 is also methylated (17-alpha-alkylated), which gives it excellent oral bioavailability — but also means it can place some strain on the liver. Unlike most SARMs, its hybrid classification and myostatin-suppressing action put it in a league of its own.
“YK-11 increases follistatin expression, which inhibits myostatin, allowing for accelerated skeletal muscle hypertrophy.”
— Tajima et al., Biological & Pharmaceutical Bulletin
It's a compound best suited for experienced users seeking aggressive muscle growth with a relatively dry and vascular finish — especially when stacked with RAD-140.
What Is RAD-140 (Testolone)?
RAD-140, also known as Testolone, is widely considered one of the most potent SARMs on the market. It was originally developed as a safer alternative to testosterone replacement therapy — designed to mimic the anabolic effects of testosterone without the unwanted side effects like prostate enlargement, testicular shrinkage, or estrogen conversion.
What makes RAD-140 so powerful is its high affinity for androgen receptors in muscle and bone, without significant activation in other tissues. This means you get the muscle-building power of testosterone with a much cleaner side effect profile.
Here’s what RAD-140 brings to the table:
→ Rapid lean muscle growth without water retention
→ Improved strength, power output, and endurance
→ Increased vascularity and hardness during a recomp or cutting phase
→ Minimal aromatization (estrogen conversion), making it ideal for dry gains
“RAD-140 exhibited potent anabolic activity in skeletal muscle and displayed a favorable tissue-selectivity profile in preclinical models.”
— Dalton et al., Journal of Medicinal Chemistry
Unlike YK-11, RAD-140 is non-methylated and gentler on the liver, making it a perfect complement in a stack. When combined, YK-11 creates the muscle-building environment, while RAD-140 drives anabolic execution — together producing gains that are dry, dense, and sustainable.
How They Work Together: Synergy Explained
The synergy between YK-11 and RAD-140 lies in their complementary mechanisms of action. While both promote muscle growth, they do so through distinct biological pathways — which, when combined, can accelerate results without dramatically increasing side effects (assuming proper cycling and support).
Here’s how the synergy works:
→ YK-11 inhibits myostatin, a growth-limiting protein that tells your body when to stop building muscle. By boosting follistatin, YK-11 removes this natural ceiling, allowing for continued hypertrophy beyond typical physiological limits.
→ RAD-140 mimics testosterone, binding directly to androgen receptors in muscle and bone tissue. It turns on the anabolic machinery that drives protein synthesis, recovery, and lean mass accrual — without the bloating or gynecomastia risk associated with anabolic steroids.
Together, this stack creates an optimal internal environment for lean growth:
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YK-11 removes the growth brakes
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RAD-140 slams the anabolic gas pedal
This makes it a powerful protocol for:
✔️ Experienced lifters entering a lean bulking or recomp phase
✔️ Bodybuilders looking for dry gains without water retention
✔️ Users seeking strength gains with minimal fat gain
“Combining androgen receptor modulators with myostatin inhibitors may enhance muscle regeneration and functional performance.”
— Gonzalez-Cadavid et al., Current Opinion in Pharmacology
For optimal synergy, this stack should be supported with proper recovery, a high-protein diet, and targeted supplements like Kre-Alkalyn Creatine and INTRA EAA to fuel muscle performance and hydration.
Benefits of YK-11 and RAD-140 Stack
Stacking YK-11 with RAD-140 offers one of the most aggressive lean mass protocols among all selective androgen receptor modulators. While either compound is effective alone, their combination leads to exponential results — particularly when muscle growth, strength, and aesthetics are the goal.
Here’s a breakdown of the primary benefits:
→ Accelerated Lean Muscle Growth
YK-11 removes the myostatin limitation, allowing muscle fibers to grow beyond their natural capacity. RAD-140 then activates the androgen receptors to maximize protein synthesis, giving you faster, more visible muscle gains.
→ Dry, Dense, and Hard Physique
Unlike bulking stacks that leave you bloated, this combination produces hard, grainy muscle with minimal water retention — especially when paired with a clean diet and effective hydration support like INTRA EAA.
→ Increased Strength and Explosiveness
RAD-140 is known for rapid strength gains. Users often report faster PRs, improved bar speed, and higher endurance under load — while YK-11 improves contractile muscle quality, making each rep more efficient.
→ Enhanced Vascularity and Muscle Fullness
With increased lean tissue and reduced subcutaneous fluid, you’ll notice improved vascularity and muscle separation. Supporting this with Clean Carbs can help maintain glycogen stores for that full, pumped look.
→ Minimal Estrogenic Side Effects
Neither compound converts to estrogen (aromatize), reducing the risk of gynecomastia, mood swings, and unwanted water weight — making this stack ideal for those who want size without puffiness.
→ Fat Loss Support via Recomp
Increased lean muscle mass naturally elevates metabolic rate. Combined with the performance benefits, this stack can help preserve or even reduce body fat levels when paired with Citrulline Malate and cardio-focused training blocks.
“RAD-140 produces anabolic effects similar to testosterone without prostate stimulation, while YK-11 promotes muscle cell growth beyond normal regulatory control.”
— Singh et al., Endocrine Reviews
Recommended Dosage and Cycle Guidelines
To maximize results and minimize side effects, it’s essential to approach the YK-11 and RAD-140 stack with a strategic dosing protocol. Both compounds are powerful on their own, and together, they demand discipline, proper timing, and support supplementation.
Here’s a typical guideline for experienced users:
➤ YK-11 Dosage
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Beginner dose: 5 mg per day
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Advanced dose: Up to 10 mg per day
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Split dosing (morning + evening) is recommended due to its short half-life (~6–10 hours)
YK-11 is methylated, meaning it's liver-active. On-cycle liver support with Liver Cleanse is highly recommended.
➤ RAD-140 Dosage
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Beginner dose: 10 mg per day
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Advanced dose: 15–20 mg per day
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Once-daily dosing is sufficient due to its longer half-life (~16–20 hours)
RAD-140 is generally well-tolerated, but suppression can still occur, especially at higher doses.
➤ Cycle Length
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Cycle duration: 8–12 weeks
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Time off = time on, including post-cycle therapy (PCT)
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Supportive supplements like ZMT and DHEA can be used throughout and after cycle
➤ Best Practices
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Start with lower doses the first week to assess tolerance
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Monitor biomarkers: liver enzymes, cholesterol, testosterone
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Stay hydrated and fuel training with Clean Carbs and INTRA EAA for recovery and energy
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Always follow up with a structured PCT protocol (next section)
“A structured SARM cycle should include a carefully dosed regimen, organ support, and PCT to avoid long-term suppression.”
— Sanchis et al., Frontiers in Pharmacology
Possible Side Effects and Safety Concerns
Although the YK-11 and RAD-140 stack is known for producing clean, dry muscle gains, it's not without potential risks — especially when run at high doses or for extended periods without proper support. Both compounds are suppressive, and YK-11 in particular may cause hepatotoxicity due to its methylated structure.
Here’s what users need to be aware of:
➤ Testosterone Suppression
Both YK-11 and RAD-140 suppress natural testosterone production by interfering with the hypothalamic-pituitary-gonadal (HPG) axis. Symptoms of suppression can include:
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Fatigue or low energy
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Reduced libido
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Mood swings or irritability
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Difficulty maintaining strength post-cycle
That’s why a full Post Cycle Therapy (PCT) is non-negotiable after using this stack.
➤ Liver Strain (YK-11)
YK-11 is methylated (17-alpha-alkylated), making it orally bioavailable but potentially toxic to the liver. Running it without on-cycle liver support can lead to elevated liver enzymes, especially if combined with alcohol or other hepatotoxic agents.
→ Support your liver with Liver Cleanse throughout the cycle.
➤ Joint Discomfort
Some users report dry or aching joints while on RAD-140 — likely due to the non-aromatizing nature of SARMs. Lower estrogen levels can reduce collagen synthesis and joint lubrication.
→ Supplementing with Collagen with Hyaluronic Acid or Krill Oil can support joint integrity.
➤ Hair Thinning or Acne
At higher doses, the androgenic activity of RAD-140 and YK-11 can trigger acne outbreaks or hair shedding in individuals genetically predisposed to androgen sensitivity (similar to DHT-like effects).
➤ Mood Changes or Aggression
Occasional reports of increased aggression, short temper, or sleep disturbances may occur — especially when running YK-11 near the 10 mg/day mark. These effects tend to resolve during PCT or after cessation.
“RAD-140 and YK-11 exhibit partial androgenic activity and suppression, making post-cycle hormonal recovery essential for long-term safety.”
— Narayanan et al., Pharmacological Reviews
Post Cycle Therapy (PCT) After YK-11 and RAD-140
Because both YK-11 and RAD-140 are suppressive, failing to run proper PCT can lead to low testosterone, muscle loss, libido crashes, and a host of hormonal issues. Even though they aren’t traditional anabolic steroids, SARMs still impact the hypothalamic-pituitary-gonadal (HPG) axis — especially when stacked.
A strong PCT protocol helps your body restart endogenous testosterone production, maintain your gains, and restore hormonal balance.
➤ Length of PCT
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Typically 4–6 weeks
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Start immediately after the last day of your cycle
➤ Pharmaceutical PCT Options
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Clomid (Clomiphene Citrate): 25–50 mg per day
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Nolvadex (Tamoxifen): 20–40 mg per day
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Some users opt to run both together in a tapering protocol
These SERMs help block estrogen receptors in the hypothalamus, stimulating luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to restart testosterone production.
➤ Natural PCT Support Stack
In addition to prescription SERMs, natural PCT supplements can help:
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DHEA (100 mg/day): Supports hormonal restoration and combats suppression
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ZMT (6 caps nightly): Contains clinically dosed magnesium, zinc, ashwagandha, and DIM for testosterone, estrogen balance, and sleep
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Greens + Reds: Antioxidant and organ support during recovery
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Liver Cleanse: Helps reduce liver enzymes post-cycle
➤ Lifestyle Tips During PCT
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Prioritize sleep (7–9 hrs/night)
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Keep protein intake high
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Train hard but avoid failure or extreme CNS fatigue
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Stay hydrated and reduce alcohol to support organ recovery
“Post-cycle therapy is essential following SARM use to recover testosterone levels and preserve lean body mass.”
— de Boer et al., Drug Testing and Analysis
Stacking Support: Supplements To Maximize Results
While the YK-11 and RAD-140 stack can deliver impressive results on its own, pairing it with the right supplement stack can dramatically improve your muscle growth, recovery, hormonal balance, and training intensity — all while protecting your health during and after the cycle.
Here’s how to support your protocol with targeted, clinically dosed supplements:
➤ Intra-Workout Support
→ INTRA EAA
Loaded with essential amino acids, coconut water, and hydrating superfoods, INTRA helps fuel your workouts, reduce muscle soreness, and preserve lean tissue during intense training.
➤ Creatine for Strength + Size
→ Kre-Alkalyn Creatine
The buffered form of creatine offers enhanced absorption and zero bloating. Pairs well with RAD-140 for strength, explosiveness, and muscle fullness.
➤ Carbohydrates for Glycogen + Pumps
→ Clean Carbs
Made from sweet potatoes, yams, oats, and blueberries — these low-glycemic carbs help fuel workouts, improve recovery, and increase cell volume without spiking insulin.
➤ Liver and Organ Protection
→ Liver Cleanse
Especially important due to YK-11’s methylation. Includes milk thistle, ALA, and NAC to keep liver enzymes in check.
➤ Hormonal Recovery
→ DHEA (100 mg/day)
→ ZMT (6 caps/night)
Both support natural testosterone production, reduce cortisol, and promote deeper sleep post-cycle.
➤ Inflammation, Joints, and Fatty Acid Balance
→ Krill Oil
High in EPA/DHA and astaxanthin for cardiovascular and joint support — especially beneficial for androgen users prone to dryness or inflammation.
➤ Recovery and Immune Function
→ Glutamine
Helps replenish muscle glycogen, boosts gut health, and supports immune resilience during taxing cycles.
This supplement stack not only protects your body during the cycle but also amplifies the results of your training. By keeping your hormones balanced, joints healthy, and workouts fueled, you’ll hold onto more muscle — and bounce back stronger post-PCT.
“Supplementing with essential amino acids, creatine, and liver support during performance-enhancing protocols can reduce risk while improving outcomes.”
— Tipton et al., Journal of the International Society of Sports Nutrition
YK-11 and RAD-140 vs Other SARMs Stacks
When choosing a SARM stack, your goal dictates the best combination. Whether you’re after mass, strength, fat loss, or overall recomposition, each stack offers different levels of effectiveness, risk, and side effect potential. The YK-11 + RAD-140 stack ranks among the most potent for lean mass and strength — but it’s also more advanced and suppressive.
Here's how it compares to other common SARM combinations:
| Stack | Primary Goal | Suppression Risk | Best For |
|---|---|---|---|
| YK-11 + RAD-140 | Lean muscle & strength | ❌❌ | Advanced users & recomp |
| LGD-4033 + MK-677 | Bulking & size | ❌❌❌ | Off-season mass gainers |
| Ostarine + Cardarine | Cutting & recomposition | ✅ Low | Beginners & fat loss |
| RAD-140 + MK-677 | Strength + muscle fullness | ❌❌ | Intermediate lifters |
| S4 + Cardarine (GW-501516) | Endurance & fat loss | ✅ Low | Athletes & CrossFit users |
✅ Why Choose YK-11 + RAD-140 for Lean Mass:
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Dual anabolic mechanisms: myostatin inhibition + AR activation
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Builds dense, dry muscle with visible vascularity
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Excellent for recomp cycles and advanced hypertrophy phases
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Requires on-cycle support and a structured PCT due to ❌ suppression and potential liver strain
“Stacking SARMs with differing mechanisms — like androgen receptor activation and myostatin inhibition — can lead to enhanced muscular outcomes.”
— Schuenke et al., European Journal of Applied Physiology
Looking for something milder? The Ostarine + Cardarine combo is beginner-friendly, non-methylated, and great for cutting phases.
Legal Status and Testing Disclaimer
As with all SARMs and research chemicals, YK-11 and RAD-140 exist in a legal gray area. While both compounds are widely available online and marketed as “research use only,” they are not approved by the FDA for human consumption and are banned by WADA and most sports federations.
Here’s what you need to know:
❌ Not Legal for Dietary Use
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YK-11 and RAD-140 are not considered dietary supplements
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They are classified as investigational drugs or research chemicals
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Any products labeled for human consumption violate current FDA guidelines
❌ Banned for Athletic Competition
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Both compounds are on the WADA Prohibited List under “other anabolic agents”
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Detection windows for RAD-140 can range from several weeks to months
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YK-11 is also detectable in blood and urine tests and is easily flagged by anti-doping labs
✅ Legal to Buy for Research Use
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Both compounds can be purchased legally in many countries when labeled “not for human consumption”
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Distribution and use for personal enhancement, however, can violate local or organizational rules
“The sale of SARMs such as RAD-140 and YK-11 as dietary supplements poses safety concerns and violates federal law.”
— U.S. Food and Drug Administration (FDA)
Disclaimer:
This article is for informational and educational purposes only. Swolverine does not sell SARMs or support the unregulated use of any performance-enhancing substances. Always consult a licensed healthcare provider before beginning any protocol involving research compounds.
Conclusion: Should You Stack YK-11 and RAD-140?
If your goal is to build dry, dense muscle mass with an edge in strength and vascularity, the combination of YK-11 and RAD-140 offers one of the most powerful SARM stacks available — but it’s not for beginners.
By pairing myostatin inhibition (YK-11) with anabolic androgen receptor activation (RAD-140), this stack creates a two-pronged approach to lean mass growth — one that few other compounds can rival. Users typically experience:
✅ Rapid improvements in lean muscle
✅ Minimal water retention
✅ Noticeable increases in strength and fullness
✅ A hard, vascular look with enhanced muscular detail
However, these results come with responsibilities:
❌ Suppression of natural testosterone
❌ Potential liver strain (especially from YK-11)
❌ The need for a structured PCT
❌ Not appropriate for drug-tested athletes
If you’re an experienced lifter with proper cycle support, on-cycle liver protection, and a clear PCT plan that includes Clomid or Nolvadex, the YK-11 + RAD-140 stack can help push your physique to elite levels.
Pair it with Clean Carbs, INTRA EAA, Kre-Alkalyn Creatine, and ZMT to maximize gains, support performance, and maintain hormonal balance from start to finish.
FAQ
Q: Can you take YK-11 and RAD-140 together safely?
→ Yes, but only with proper dosing, cycle length, and on-cycle support. Both are suppressive, and YK-11 is methylated, so liver protection and PCT are essential.
Q: How long should a YK-11 and RAD-140 cycle last?
→ Most users run the stack for 8–12 weeks, followed by a 4–6 week post cycle therapy (PCT). Time off should equal time on.
Q: What’s the best PCT protocol after this stack?
→ Either Clomid (25–50 mg/day) or Nolvadex (20–40 mg/day) for 4–6 weeks, supported by DHEA and ZMT.
Q: Can women use this stack?
→ Not recommended. Both compounds have strong androgenic activity, and side effects in women can include virilization and hormonal disruption. Safer options include Cardarine or MK-677.
Q: Is YK-11 legal to buy and use?
→ It’s legal to purchase for research purposes in many countries but is not approved for human consumption. It’s banned in competitive sports and not regulated for safety or purity.
Q: What supplements should I take with this stack?
→ Key supplements include:
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INTRA EAA for hydration and recovery
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Liver Cleanse for organ support
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Kre-Alkalyn for strength and fullness
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Clean Carbs for glycogen support
