Ostarine MK 2866 SARM: Benefits, Uses, Dosage

Ever heard of Ostarine MK 2866? Bodybuilders all throughout the world have sought after the use of this SARM since it’s a safe alternative to steroids that can get you lean mass gains without the major side effects.

In this article, I’ll clarify what exactly SARMs are and why Ostarine MK 2866 may be the best option for you. My 40+ years in the bodybuilding world have educated me on this topic back to front and I’m here to guide you through the process of making an educated decision about whether or not to take this SARM.

Warning: The content on Muscleandbrawn.com and the information included in this article is intended for entertainment and informational purposes only. It is not intended nor implied to be a substitute for professional medical advice. Prior to buying anything, check that it is compliant where you live with your current government laws. We frequently mention research chemicals that are not made for human consumption. Therefore, before purchasing any product for personal use, consult with your doctor or healthcare provider first.

What is Ostarine MK 2866?

Ostarine MK 2866 is an orally-active, non-steroidal selective androgen receptor modulator (SARM ). It is manufactured by the company GTx, Inc. and is regarded as one of the safest, best-tested, and most effective bodybuilding SARMs available.

It’s considered to be the best SARM for beginners and it is most commonly used during bulking and recomp phases.

In a 12-week double-blind placebo-controlled phase II clinical trial involving 120 healthy elderly men and postmenopausal women, ostarine was shown to significantly increase muscle issues, improve physical function and insulin sensitivity. [1]

How Does Ostarine Work?

Ostarine selectively binds itself to proteins within the body that are called androgen receptors. When attached to the androgen protein, it communicates the message for it to get bigger.

Unlike anabolic steroids, Ostarine does not convert to estrogen or DHT. [2]

Benefits of Ostarine

Ostarine, like other SARMs, is selective in the proteins that it targets which means that it does not enter parts of your body that may cause serious problems, such as the liver or pancreas. It also does not affect your androgenic, or sexual, characteristics and it exclusively works on your anabolic, i.e. muscle building, characteristics.

Ostarine is popular among bodybuilders because it has been shown to add significant muscle mass and reduce body fat. This makes it the most useful SARM for body recomposition and the average mass increases that have been reported anecdotally over an 8 week cycle of Ostarine (at a dosage of 25mg per day) appear to between between 6 and 9 pounds of lean muscle mass.

Ostarine can also be used as part of a cutting cycle. The best way to use it towards cutting is to lower the daily dosage to between 15 and 20 mg per day and be sure to reduce your daily caloric intake.

Is Ostarine Legal?

Ostarine is legal, but only for research purposes. It has not been approved by the US Food & Drug Administration (FDA) and as a result cannot be sold as a dietary supplement.

It’s widely available on the internet but websites that sell selective androgen receptor modulators must market them, not as lean body mass builders or fat loss agents, but as tools for research only.

The FDA is beginning to clamp down on online sellers of SARMs and have recently shut down a large retailer and clearly have others in their firing line. Ostarine is also on the World Anti Doping Agency list of prohibited substances.

Ostarine Summary


Ostarine is an orally-active, non-steroidal selective androgen receptor modulator (SARM ).

It’s considered to be the best SARM for beginners and it is most commonly used during bulking and recomp phases.

In a 12-week double-blind placebo-controlled phase II clinical trial involving 120 healthy elderly men and postmenopausal women, ostarine was shown to significantly increase muscle issues, and improve physical function and insulin sensitivity. [4]

Ostarine selectively binds itself to proteins within the body that are called androgen receptors. When attached to the androgen protein, it communicates the message for it to get bigger.

Unlike anabolic steroids, Ostarine does not convert to estrogen or DHT. [5]

Ostarine is legal, but only for research purposes. It has not been approved by the US Food & Drug Administration (FDA) and as a result, cannot be sold as a dietary supplement.

Ostarine MK-2866 Overview

⭐️ Top Benefits: Muscle growth, strength gain, fat loss
🧪 Form: Liquid, Powder
⌛️ Cycle Length: 6 – 7 weeks
💰 Average Cost: $54.99
❤️‍🩹 Side Effects: Stomach pain, headaches, cholesterol increase, liver strain, and hypertension
☢️ Dangers: Hepatotoxicity
📚 Best Stack: MK-677 / Cardarine / RAD 140
PCT Required: Yes
🧍‍♂️🧍‍♀️Men/Women: Men and Women (Lower dose)
🔄 See Results
➡️ Go to the Full review

  • Better recovery
  • Improved fat loss
  • Massive muscle gains
  • Stomach pain
  • Headaches
  • Liver toxicity
  • Hypertension
  • Cholesterol

Who Should Use Ostarine?

Unless you are working out hard consistently, you cannot quality muscle, regardless of what chemicals you put in your body. You also need to have your diet on point in order to reach your muscle-building goals.

If you have both your training and diet in place, then Ostarine may be suitable for you as an aid to gaining mass, cutting, or recomping your body.

Ostarine Cycle

You should start with an 8-week MK 2866 cycle and take 25 mg of Ostarine per day first thing in the morning.

Your subsequent cycles can be extended to 10 to 12 weeks if you have a good tolerance to your first cycle.

Ostarine Dosage

The recommended starting dosage for Ostarine is 25-30 mg for muscle gain. If you are taking it for cutting, you should reduce your dosage to 15-20 mg per day.

Ostarine For Bodybuilding

When using Ostarine for bodybuilding purposes, we suggest following an initial 8 week cycle.

Begin with 25 mg per day and on subsequent cycles you can experiment with your dosages and cycle lengths to a maximum of 30 mg and 12 weeks.

The amount of testosterone suppression that occurs when you go on an Ostarine cycle differs between individuals and is dependent on the length of the cycle and dosage. Not all cycles will require PCT cycling.

To be safe, however, we suggest that you go on a 3 week PCT cycle following your use of MK 2866 as a matter of course. It’s best to use Clomid as your PCT agent, taking 10 mg per day.

Ostarine For Cutting

Ostarine is an effective cutting agent and we recommend starting with 10 mg per day on your first 8-week cycle. Make sure that you are also maintaining a daily caloric deficit for the entire period of your cycle in order to achieve your goal.

Ostarine For Women

Ostarine is generally considered to be the mildest selective androgen receptor modulator. However, females should use a lower dosage than guys.

We recommend starting with 15 mg per day for mass gain and 10 mg per day for cutting over an 8 week cycle.

Ostarine Stack

Ostarine can be stacked with other SARMs for an even greater effect. When it comes to mass building, we recommend the following 8 week stack:

  • Anadarine S4 – 25mg morning – 25mg evening
  • Ostarine MK 2866 – 25mg per day
  • GW501516 – 20mg 30 minutes before your workout

Here is an advanced cutting stack that also follows an 8 week cycle:

  • Ostaraine – 20mg in the morning
  • Cardarine – 30 mg in the morning
  • SR9009 – 29 mg in the morning
  • Anadarine – 50 mg in the evening

Ostarine Side Effects

There have been no major side effects associated with the use of Ostarine. However, we strongly recommend keeping your daily dosage to no more than 30 grams to ensure safety and minimize the potential side effects of nausea, heartburn, diarrhea and stomach pain.

SARMs have not been around long enough for us to make a categorical statement on the long term safety and side effects of using MK 2866.

Ostarine PCT

Ostarine may have a mildly suppressive effect on your body’s natural testosterone production, depending on the dosage and length of the cycle. For that reason, we recommend following your cycle with a 3 week PCT cycle using 10 mg of Clomid daily.

Does Ostarine Work?

Yes, Ostarine definitely does work. It has been shown to increase muscle mass in patients in numerous Phase One Clinical Trials. In addition, many users around the world have documented their results online. A typical cycle of MK2866 over a period of 8 weeks, when coupled with hard, heavy training and a mass gaining diet can pack on between 6 and 9 pounds of lean muscle mass.

Is Ostarine Safe?

Ostarine is considered to be the safest SARM that exists. Because of its selective nature, it will not cause harm to your organs or produce negative androgenic effects. As noted in the side effects section above, some people have noted minor effects but non major negative side effects have been reported with sensibsle use of Ostarine.

Where to Buy Ostarine

Ostarine is available online through a number of retailers. We caution you, however, to be highly selective in choosing your vendor. Avoid any SARMs that come from Asia. Many that are sold on general merchandise sites such as Alibaba and Amazon can be traced back to China. Forunately, a number of highly reputable online vendors have emerged in recent times. Our favorite and the one that we recommend is science.bio

Ostarine vs RAD140

RAD140 is more powerful than Ostarine and we do not recommend it for your first cycle. If, however, you follow a 25 mg Ostarine mass gaining cycle for 8 weeks with good results and no bad effects, you may follow it up with the more potent RAD 140 for a similar cycle.

Most experienced users will go with RAD 140 for bulking and Ostarine, at a lower dosage, for cutting.

Ostarine vs Ligandrol

Ligandrol is another effective SARM for bulking. If you are looking to pack on lean mass fast then this is a good bet for you.

In terms of pure mass gains, Ligandrol is more effective than Ostarine. Ligandrol is also an excellent choice when it comes to pure strength gains.

Ostarine vs S4

Both Ostarine and Andarine S4 are used for cutting though, as we have seen, Ostarine, when taken at a higher dose, is also an effective buking agent.

It should be noted that Ostarine has a better safety profile. In fact, S4 was abandoned in clinical trials due to some safety concerns.

In terms of fat loss while preserving muscle, S4 will probably produce better results. This, however, needs to be weighed against the better safety profile of Ostarine.

Ostarine vs YK-11

YK-11 is unique in the world of SARMs due to its ability to inhibit Myostatin, which is a protein that prevents muscle growth. This makes it a special and very potent mass building agent.

As such, it is a better bulking agent than Ostarine. However, Ostarine wins out over YK-11 in its ability as a cutting agent.

Should You Take Ostarine?

If you are going to take a SARM, then Ostarine is the natural introductory agent. This is the mildest and safest SARM available with no major recognized side effects. Follow a conservative 8-week cycle at 25 mg per day and follow it with a 3 week PCT using 10 mg of Clomid per day.

You should only consider using this, or any other SARM, however, if you are beyond puberty, have been training for at least a year and are consistently working out intensely while following a sensible clean diet that is geared toward your reason for taking the SARM in the first place.

Still Have Questions?

Drop us a comment down below and one of our expert coaches will respond to it. We’ll also be answering questions on our Instagram!

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[1] Selective Androgen Receptor Modulators (SARMs): USADA. (2020, July 27). Retrieved from https://www.usada.org/spirit-of-sport/education/selective-androgen-receptor-modulators-sarms-prohibited-class-anabolic-agents/

[2] Substance Profile: What athletes need to know about ostarine: USADA. (2017, Feb 6). Retrieved from https://www.usada.org/spirit-of-sport/education/substance-profile-ostarine/

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Steve Theunissen

Steve Theunissen | Writer

Steve Theunissen is a seasoned fitness professional with 25+ years of experience. He has multiple certifications from the International Sports Sciences Association, including Certified Personal Trainer, Fitness Nutrition Certification, and Strength and Conditioning Certification. He's a knowledgeable and experienced bodybuilding coach, combining his passion for fitness with his writing skills to educate and inspire. Whether starting out or looking to take training to the next level, Steve Theunissen is the ideal coach to help reach fitness goals.

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Josh Tiller
5 months ago

MK2866 is suppressive and can cause gynecomastia.

Cam Jackson
8 days ago

What’s a good ostarine and cardarine cycle for someone looking to add lean mass?

Chemical Structure

Mechanism of Action

Ostarine attaches to specific proteins in the muscle cells called the Androgen receptors. Once bound to these receptors, it stimulates the muscle cells to increase the rate of protein synthesis, leading to muscle gain and improved recovery after an injury.

Class of Compound


Street Names

Enobosarm, 841205-47-8, GTx-024, MK-2866


  • Improves muscle mass
  • Improves muscle endurance and recovery
  • Improves vascularity

Side Effects and Dangers

  • Stomach pain, Diarrhoea, and constipation
  • Strain the liver
  • May cause depression and hypertension
  • Risk of heart attack and stroke

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