MK-2866 vs RAD-140: Comparing Two Popular SARMs

Written by James C., M.S.(C), PT

| Published on

Fact Checked

MK-2866 (Ostarine) and RAD-140 (Testolone) are both popular selective androgen receptor modulators (SARMs) that have gained considerable attention in the fitness and bodybuilding community. While they share similarities as members of the SARMs family, their mechanisms of action, benefits, side effects, and recommended dosages differ. This article aims to provide a comprehensive comparison between MK-2866 and RAD-140, allowing readers to make an informed decision regarding which compound is best suited for their fitness goals.

MK-2866 vs RAD-140: Comparing Two Popular SARMs

SARMs like MK-2866 and RAD-140 are designed to selectively target androgen receptors in muscle and bone tissues, promoting muscle growth and enhancing strength without many of the adverse effects associated with traditional anabolic steroids. However, despite their shared objective, MK-2866 and RAD-140 possess distinct profiles that make them more suited for specific goals like muscle gain, fat loss, or endurance improvement.

Key Takeaways

  • MK-2866 and RAD-140 are both SARMs, but they differ in their mechanisms, benefits, and side effects.
  • Usage and dosage recommendations vary between the two compounds based on individual goals and tolerance.
  • Post-cycle therapy and awareness of potential risks are essential when using either MK-2866 or RAD-140.

Understanding MK-2866 and RAD-140

MK-2866, commonly known as Ostarine, and RAD-140, also known as Testolone, are both Selective Androgen Receptor Modulators (SARMs). They have been developed to target androgen receptors in the body, aiming to selectively stimulate anabolic effects in muscles and bones, while minimizing undesirable side effects.

Best Legal SARMs
Top-Rated Legal SARMs Alternatives in 2024

Looking for the best SARMs alternatives that can help you achieve rapid muscle growth and fast fat loss without all the side-effects?

Learn More How It Works

Ostarine (MK-2866) is a well-researched and mild SARM, primarily known for its potential use in treating muscle-wasting disorders. It is currently in Phase 2 clinical trials. As a result of its mild nature, it is considered suitable for beginners or individuals looking for modest muscle gains while minimizing side effects. Ostarine is often utilized in the cutting phase, as it aids in retaining lean muscle mass during calorie deficits.

Here are some key characteristics of Ostarine:

  • Mild in potency
  • Ideal for cutting phase
  • Suitable for beginners
  • Fewer side effects

On the other hand, Testolone (RAD-140) is a more potent SARM, best suited for advanced users seeking significant muscle gains. RAD-140 is typically used during the bulking phase and has been reported to provide almost twice the muscle gains compared to Ostarine. However, it may carry a higher risk of side effects.

Here are some key characteristics of Testolone:

  • Higher potency
  • Ideal for bulking phase
  • Suitable for advanced users
  • Potential for more side effects

It is important to note that while both compounds are popular among bodybuilders and athletes, they are not approved by the FDA. The safety and efficacy of SARMs are still being researched, and users must be cautious about their consumption. Always consult with a medical professional before starting any supplement regimen.

Mechanism of Action

MK-2866 and RAD-140 mechanism of actions

Ostarine (MK-2866) and RAD-140 (Testolone) are both types of Selective Androgen Receptor Modulators (SARMs). They share similarities in how they function, yet exhibit different results on the body. In this section, we will discuss how each of these SARMs operates by interacting with androgen receptors in the body.

Ostarine works by selectively binding to androgen receptors in skeletal muscle tissue, stimulating an increase in protein synthesis and resulting in muscle growth. This selective action allows Ostarine to avoid many of the negative side effects associated with traditional anabolic steroids, such as liver toxicity or cardiovascular issues. Additionally, it has shown potential in aiding joint health and even fat reduction.

RAD-140, on the other hand, has a distinctive mechanism of action. It also binds to androgen receptors, but with a higher affinity than Ostarine. This leads to an even more powerful anabolic effect, resulting in substantial muscle growth and strength gains. Furthermore, RAD-140 has shown to have potential neuroprotective effects, with some studies suggesting that it could help maintain neurological function and prevent age-related cognitive decline.

It’s worth mentioning that both Ostarine and RAD-140 exhibit tissue-selective activity, meaning they primarily target skeletal muscle without significantly impacting other tissues such as the prostate or liver. This characteristic reduces the risk of undesirable side effects often associated with anabolic steroid use.

In summary, Ostarine and RAD-140 share common ground as SARMs by selectively binding to androgen receptors. While Ostarine focuses on promoting muscle growth, joint health, and fat reduction, RAD-140 shines in its ability to produce remarkable muscle gains, strength increases, and potential neuroprotective effects. Each of these SARMs offers unique benefits, making them powerful tools for individuals seeking to enhance their physique and overall well-being.

Benefits and Performance Enhancement

Strength and Stamina

Both MK-2866 (Ostarine) and RAD-140 (Testolone) are known for their ability to enhance strength and stamina. Users typically report increased ability to lift heavier weights, along with improved endurance during training sessions. This allows individuals to push themselves harder and achieve better overall performance.

  • MK-2866: It is often praised for its ability to enhance strength and endurance without significant side effects compared to steroids.
  • RAD-140: Known for its potent impact on strength and stamina enhancement, making it a popular choice among professional athletes and bodybuilders.

Muscle Growth and Fat Loss

MK-2866 and RAD-140 have shown to promote muscle growth and aid fat loss, which contributes to their popularity among bodybuilders and fitness enthusiasts. They work by selectively binding to androgen receptors, ensuring optimal muscle growth while minimizing fat gain.

  • MK-2866: Provides a balanced effect on muscle growth and fat loss, making it suitable for both bulking and cutting cycles. Users often report steady muscle gains and reduced body fat percentage.
  • RAD-140: Potentially more intense in promoting muscle growth compared to MK-2866, making it a popular choice for bulking cycles. It also contributes to fat loss, although MK-2866 might be slightly more effective in this area.

Bone Health

In addition to their well-known benefits on strength, stamina, and muscle growth, MK-2866 and RAD-140 have also been researched for their potential effects on bone health.

  • MK-2866: Studies have shown that MK-2866 can increase bone mineral density, which may prevent diseases like osteoporosis and fractures. It is particularly beneficial for individuals with low bone density or at high risk of bone-related issues.
  • RAD-140: Although limited information is available on its direct impact on bone health, RAD-140 is thought to have similar bone-strengthening properties due to its selective binding to androgen receptors.

Usage and Dosage

Usage and Dosage of MK-2866 and RAD-140

When comparing MK-2866 (Ostarine) and RAD-140 (Testolone), it’s essential to consider the specific usage and dosage recommendations for each SARM. The following subsections discuss the optimal cycle length, dosage, and applications in both bulking and cutting phases.

Cycle Length and Dosage

MK-2866 (Ostarine):

MK-2866 is typically used for 8-12 weeks at a time, with a recommended dosage of 10-30 mg per day, depending on the user’s experience and goals. It is advisable to start with a lower dosage and gradually increase as needed. A rest period of 4-6 weeks is recommended between cycles.

RAD-140 (Testolone):

RAD-140 cycles usually last 8-10 weeks, and the recommended daily dosage is between 10 mg to 20 mg. Like Ostarine, users should start with a lower dosage and incrementally increase based on their experience and objectives. A post-cycle rest period of around 6-8 weeks is advised.

Bulking vs Cutting

MK-2866 (Ostarine):

Ostarine is often considered a more versatile SARM, suitable for both bulking and cutting. In a bulking phase, users can expect to gain lean muscle mass while having minimal impact on body fat levels. A typical dosage for bulking purposes lies between 20-30 mg per day. During a cutting phase, Ostarine helps preserve muscle mass and promote fat loss. Users usually take a dosage of 10-20 mg daily in this situation to enhance body composition or achieve body recomposition.

RAD-140 (Testolone):

RAD-140 is a powerful SARM primarily utilized for bulking purposes due to its potent muscle-building effects. In a bulking cycle, users often take a dosage of 10-20 mg daily, aiming to increase muscle mass and improve overall strength, while potentially experiencing a slight increase in body fat.

Although not specifically designed for cutting, some users incorporate RAD-140 in their cutting cycles with a lower daily dosage of 10 mg. This approach might aid in muscle retention and support modest fat loss. However, it’s essential to maintain a proper diet and exercise regimen during the cutting phase to optimize results.

In conclusion, both MK-2866 and RAD-140 have distinct applications and dosage recommendations, depending on the desired goals and cycle length. When choosing between these two SARMs, it’s essential to consider the user’s objectives and experience to make an informed decision.

Comparison of Mk-2866 and Rad-140

Mk-2866, also known as Ostarine or Enobosarm, and Rad-140, popularly known as Testolone, are two popular selective androgen receptor modulators (SARMs) that have gained a following in the fitness community for their impressive anabolic effects, such as strength and muscle gains. In this section, we will compare these two SARMs, focusing on their key differences and benefits.

  • Strength Gains: While both Ostarine and Testolone have shown potential for increasing strength, Rad-140 is generally considered to be the more potent option. Milligram per milligram, Rad-140 is more powerful, offering users the possibility to experience more prominent strength gains.
  • Muscle Gains: Once again, Rad-140 gains an edge when it comes to promoting muscle growth. Compared to Ostarine, Testolone can be more effective at enhancing the increase of lean muscle mass. Users typically report improved muscle size and density with Rad-140.
  • Fat Loss: While both SARMs can contribute to weight loss, Ostarine is often favored specifically for its fat loss properties. Mk-2866, better known for helping with cutting, can assist in shedding excess body fat while retaining lean muscle mass, making it a popular choice among those looking to lean down.
  • Side Effects: Generally speaking, Ostarine comes with fewer side effects compared to Rad-140. As a milder SARM, Mk-2866 typically presents fewer risks, while Testolone, being more potent, is also known to come with a higher possibility of side effects. Users should be aware of the potential risks involved with each SARM and always consult with a healthcare professional before beginning use.

A summary table for an at-a-glance comparison:

AspectMK-2866 (Ostarine)RAD-140 (Testolone)
Strength Gains
Muscle Gains
Fat Loss
Side EffectsMildModerate

In conclusion, Rad-140 (Testolone) is generally considered better for strength and muscle gains, although Ostarine (Mk-2866) is known to excel at fat loss and offer a more mild risk profile. The choice between these two SARMs should depend upon individual goals and preferences, keeping the potential benefits and side effects in mind. Always consult a healthcare professional before starting any SARM cycle.

Side Effects and Potential Risks

Side Effects and Potential Risks of MK-2866 and RAD-140

In this section, we will discuss the side effects and potential risks associated with the use of MK-2866 (Ostarine) and RAD-140. Selective androgen receptor modulators (SARMs) are known for their potential to promote muscle growth and enhance strength, but they also come with some side effects.

Best Legal SARMs
Top-Rated Legal SARMs Alternatives in 2024

Looking for the best SARMs alternatives that can help you achieve rapid muscle growth and fast fat loss without all the side-effects?

Learn More How It Works

Common Side Effects

MK-2866 (Ostarine)

  • Hair loss: Some users may experience hair thinning or shedding during Ostarine cycles.
  • Nausea: A small number of users may experience nausea or indigestion.
  • Headache: Ostarine can occasionally cause headaches in sensitive individuals.
  • Constipation: A minor side effect that can be managed with adequate fluid intake and dietary modifications.


  • Hair loss: RAD-140 users may also experience hair loss similar to Ostarine users.
  • Nausea: RAD-140 can cause nausea in some individuals.
  • Headache: As with Ostarine, RAD-140 can lead to headaches.
  • Diarrhea: Some users may experience diarrheal episodes during RAD-140 cycles.
  • Constipation: Similar to Ostarine, constipation may be a minor issue with RAD-140 use.

Long-Term Risks

Both MK-2866 and RAD-140 are relatively new compounds, and there is limited research available on their long-term effects. However, some potential long-term risks associated with the use of these compounds should be noted.

  • Liver toxicity (hepatotoxicity): Although studies are limited, there is the potential for liver toxicity with the use of SARMs, including MK-2866 and RAD-140. Users are advised to monitor their liver function and take appropriate precautions.
  • Heart attack: The long-term use of these compounds may increase the risk of cardiovascular events, such as heart attacks. However, more research is needed to confirm this potential risk.
  • Suppressed natural testosterone levels: Prolonged use of SARMs can result in the suppression of natural testosterone levels, which can lead to side effects like erectile dysfunction, loss of bone density, muscle weakness, weight gain, and depression. To minimize these risks, users should adhere to appropriate cycle lengths and implement post-cycle therapy (PCT) when directed by a medical professional.

While the FDA has not approved SARMs, including MK-2866 and RAD-140, for human use, they remain popular among bodybuilding and fitness enthusiasts. It is essential for users to understand the potential side effects and long-term risks associated with these compounds and make informed decisions about their use.

Post Cycle Therapy

difference in post-cycle therapy for MK-2866 and RAD-140

Post Cycle Therapy (PCT) is an essential part of any SARMs or steroid cycle, including those involving MK-2866 (Ostarine) and RAD-140 (Testolone). PCT helps the body recover from the possible side effects of these compounds, particularly testosterone suppression. This section will discuss the importance of post-cycle therapy and provide recommendations for a proper PCT protocol.

During a SARMs cycle, the body’s natural testosterone production may be reduced due to the introduction of exogenous compounds that mimic the effects of testosterone. Both Ostarine and Testolone are selective androgen receptor modulators (SARMs) known to promote muscle growth and enhance strength. It is crucial to undergo PCT after completing a cycle to restore hormone balance and support overall health.

The severity of testosterone suppression varies depending on the SARM compound, dosage, and duration of the cycle. Generally, Ostarine is considered milder, while RAD-140 is the stronger option, potentially leading to a more significant suppression in natural testosterone production. Therefore, different PCT protocols may be suitable for each SARM.

Here are some recommended PCT components specific to each SARM:

  • Ostarine (MK-2866): Since it is milder than RAD-140, a modest PCT regimen is generally adequate for Ostarine users. Over-the-counter supplements, such as natural testosterone boosters, can be sufficient for restoring natural hormone levels.
  • RAD-140 (Testolone): Due to its stronger impact on testosterone suppression, a more intensive PCT is necessary for RAD-140 users. Prescription medications like Nolvadex or Clomid are typically employed to help stimulate the production of natural testosterone and regulate hormone levels effectively.

It’s beneficial to tailor the PCT approach according to the user’s experience, the specific SARM, and the intensity of the cycle. Consulting with a healthcare professional can provide personalized advice and ensure a successful recovery.

In conclusion, post-cycle therapy is an indispensable component of any SARMs or steroid cycle. By properly implementing a PCT tailored to the specific SARM used – Ostarine or RAD-140 – users can support their hormonal recovery process, ensuring long-term health and performance benefits.

Regulatory Status and FDA Approval

Selective Androgen Receptor Modulators (SARMs), including MK-2866 (Ostarine) and RAD-140 (Testolone), are gaining popularity in fitness and bodybuilding communities. However, it’s essential to understand their current regulatory status in terms of FDA approval.

As of now, neither MK-2866 nor RAD-140 has been approved by the FDA for any medical use. Both of these SARMs are considered investigational new drugs and are still undergoing research to determine their safety and effectiveness. The FDA has issued warnings to manufacturers and distributors of SARMs, emphasizing that these compounds are not approved for human consumption.

In the search results, there’s a specific mention of a warning letter issued by the FDA on June 12, 2023, to Warrior Labz SARMS, which included RAD-140. This indicates the agency’s active involvement in monitoring the distribution and sale of such substances.

Despite the lack of FDA approval, SARMs like MK-2866 and RAD-140 are readily available in the market as “research chemicals” or dietary supplements. It’s crucial for consumers to be aware of the potential risks associated with using unapproved substances and potential adverse effects on their health.

In summary, MK-2866 (Ostarine) and RAD-140 (Testolone) haven’t received FDA approval, which means they are not considered safe for human consumption. Users should exercise caution and be aware of the potential health risks associated with using these SARMs.

MK-2866 and RAD-140 in Bodybuilding

Best Legal SARMs
Top-Rated Legal SARMs Alternatives in 2024

Looking for the best SARMs alternatives that can help you achieve rapid muscle growth and fast fat loss without all the side-effects?

Learn More How It Works

Use in Professional Bodybuilding

MK-2866, also known as Ostarine, and RAD-140, or Testolone, are popular Selective Androgen Receptor Modulators (SARMs) used in professional bodybuilding. While both compounds serve to greatly increase muscle mass, RAD-140 is more potent, making it the better choice for advanced lifters. On the other hand, Ostarine is recommended for beginners due to its milder effects and higher tolerability.

Beginner’s Guide

For those who are new to bodybuilding, starting with Ostarine (MK-2866) is beneficial. It is known to produce steady and consistent muscle gains with limited side effects. A typical Ostarine cycle for beginners would involve a daily dosage of 10mg for 8 weeks.

In contrast, RAD-140 would be suitable for more experienced lifters. The daily dosage for RAD-140 should be around 10mg for a duration of 8 weeks. It’s important to carefully monitor performance and muscle development to ensure the body responds well to the increased potency of RAD-140.

Diet and Nutrition

A key component to the success of using MK-2866 and RAD-140 in bodybuilding is to maintain a balanced diet and proper nutrition during the cycle. Consuming adequate protein, carbohydrates, and healthy fats will promote muscle growth and enable lifters to maximize their gains.

As an example, a meal plan while on a SARMs cycle could include:

  • Protein: Lean meats, fish, eggs, dairy, and plant-based options
  • Carbohydrates: Whole grains, brown rice, starchy vegetables, and fruits
  • Fats: Avocado, olive oil, nuts, seeds, and fatty fish

Additionally, adequate hydration is essential for optimal performance and recovery.

Training and Personal Records

When incorporating MK-2866 or RAD-140 into a bodybuilding routine, it’s crucial to follow an appropriate training program. This will enable lifters to gradually increase weights, volume, and intensity, thereby achieving greater gains and improvements to their personal records. Consistency, proper form, and balanced routines focusing on all muscle groups are essential elements in obtaining desired results.

Comparative Results and Efficiency

While both Ostarine and RAD-140 can lead to impressive gains, RAD-140 is considered to be more potent and efficient at building muscle mass. This makes it more suitable for experienced lifters who aim to achieve bigger and leaner muscles at a faster rate. Ostarine, on the other hand, tends to yield slower but steady gains, making it an ideal starting point for beginners. Careful monitoring, adherence to dosage guidelines, and patience are key components for maximizing the effectiveness of both SARMs in bodybuilding.

Frequently Asked Questions

What are the main differences between MK-2866 and RAD-140?

MK-2866, also known as Ostarine, and RAD-140, also known as Testolone, are both selective androgen receptor modulators (SARMs). However, they have different effects on muscle growth and strength enhancement. Ostarine is generally milder, making it suitable for beginners and those looking for steady muscle gain with minimal side effects. In comparison, RAD-140 is more potent and has a stronger anabolic effect, resulting in faster muscle growth and increased strength.

Which compound is more effective for muscle growth?

Both MK-2866 and RAD-140 promote muscle growth, but RAD-140 is considered more effective due to its higher anabolic potency. Users typically experience more rapid muscle growth and increased strength when using RAD-140 as compared to Ostarine.

Which SARM has fewer side effects, MK-2866 or RAD-140?

MK-2866, or Ostarine, generally has fewer side effects than RAD-140 due to its milder nature. However, both compounds have relatively manageable side effects as compared to traditional anabolic steroids. Some possible side effects may include temporary suppression of testosterone and mild liver strain, but these are typically less severe than those associated with anabolic steroids.

Can MK-2866 and RAD-140 be stacked together for better results?

Yes, MK-2866 and RAD-140 can be stacked together for improved results. Combining the two SARMs can lead to synergistic effects, enhancing muscle growth, fat loss, and overall performance. However, it’s important to closely monitor dosages and cycle duration to minimize potential side effects and hormonal imbalances.

Is RAD-140 more potent than MK-2866?

RAD-140 is generally considered more potent than MK-2866. Its higher anabolic potency results in more significant muscle gains and strength improvements. However, with increased potency comes the potential for more severe side effects. Users should carefully consider their goals and experience levels before choosing either compound.

Which SARM is safer for use, MK-2866 or RAD-140?

Both SARMs are relatively safe when compared to anabolic steroids, but MK-2866 (Ostarine) is considered safer due to its milder nature and fewer side effects. As always, it’s crucial to follow proper dosing protocols and cycle durations to ensure safety and minimize potential adverse effects.

My recommended supplements

Testo Booster
Natural Testosterone Booster For Men

By cutting out the middle-men we were able to produce super high-quality booster packed with all the right ingredients to stimulate natural testosterone production.

Buy Now How It Works
Powerful Fat Burner
Fat Burner Diet Drops: Ultra Fat Loss Supercharger

Are you serious about FINALLY losing that stubborn belly fat? Then this is for you. Powerful fat burner that helps you supercharge your metabolism for fast results.

Get 25% OFF How It Works
Testosterone Booster
TestoPrime | Natural Testosterone Booster

Unleash the full testosterone-producing potential in your body. Improve muscle growth and increase fat loss fast.

Learn more Read My Review
Best For Bulking
Best Bulking Stack For Muscle Growth

Try this for rapid size, strength, and muscle-building results.

Learn more Read My Review

Leave a Comment