Ostarine MK-2866 Guide: How To Use, Side-Effects & Benefits

Ostarine (MK-2866) is a Selective Androgen Receptor Modulator (SARM) widely known to be a potent muscle-building compound that’s currently used by bodybuilders to boost their performance.

Ostarine is also used to treat conditions such as muscle wasting and osteoporosis. Although developers are still researching its benefits and side effects it’s still hugely popular for its muscle-building effects.

In this guide, we’ll show you the benefits, side effects, and uses of the SARM.

Before we get into the details, though, it’s essential to note that the developers of Ostarine are still researching the compound. Its exact effects and side effects are still under investigation, but we’ll present all of the latest clinical results that we’ve been able to find.

Most importantly, we do not condone the use of Ostarine, nor do we advise you to buy, use, or sell it.

What is Ostarine (MK-2866)


Ostarine—also known as Enobosarm or MK-2866—is a Selective Androgen Receptor Modulator (SARM), currently under development by GTx Inc.

Ostarine binds to the androgen receptor (AR) and selectively stimulates AR signaling in muscle and bone tissues. This process thereby creates similar benefits as testosterone without the undesired hormonal side effects.

Taking Ostarine is supposed to help build lean muscle mass and stronger bones without causing complications such as prostate enlargement or hair loss.

Furthermore, GTx is currently conducting a Phase III clinical trial of Ostarine for the treatment of muscle wasting in patients with cancer but the results have yet to be published.

What is known, though, is that Ostarine shows promise as a SARM and is currently being used by bodybuilders as a performance-enhancing compound.

It falls into a similar category as other products, such as LGD-4033 and RAD-140, which are both well-known within the community for their abilities to build dense muscle mass.

Ostarine enobosarm

Unlike other compounds, though, Ostarine has gained a reputation for being a ‘mild’ supplement. Ongoing research suggests that it doesn’t suppress your natural testosterone, allowing you to take it without experiencing harsh side effects.

This sets it apart from other SARM products, such as Testolone, which are notorious for causing hormonal imbalances.

As a Phase III research compound, MK-2866 currently isn’t available to the general public but it has been listed for sale on a variety of websites.

It’s difficult to authenticate the sources for these sites, making it basically impossible to gauge whether the products they’re selling are genuine MK-2866 supplements.

The FDA has already issued a public warning stating that supplements containing SARMS, such as Ostarine, could be dangerous and has advised athletes to avoid taking them.

If you decide to purchase Ostarine from a third-party website, be careful when taking it and be sure to follow the manufacturer’s instructions.

What to Expect from Ostarine?

If you compare Ostarine to other SARMs, such as Ligandrol and Testolone, you’ll find that it’s pretty mild. It can help develop muscle mass but at lower rates than similar products.

This comes with the benefit of not causing significant negative side effects, though. Nonetheless, it’s one of the most commonly used SARMs, taken to help enhance athletic performance, boost muscular generation, and improve bone density.

Keep in mind as you read, though, that all of these effects are based on anecdotal experience and scientific evidence has yet to be published. Always remember that these compounds are intended for research and laboratory use only.

Increased Muscle Mass

Ostarine was originally developed as a research compound meant to treat muscular degenerative diseases in the elderly. Although researchers are still investigating its possible use as a treatment, it has widely been coopted by the bodybuilding community as an anabolic compound.

When Ostarine binds to an androgen receptor (AR), it causes muscular growth in a similar way to how testosterone works. Additionally, since Ostarine doesn’t attach to the estrogen receptor (ER), it can’t cause any of the side effects typically associated with estrogens such as water retention, gynecomastia, or fat gain.

Since Ostarine can accomplish all of this without causing the side effects typically associated with testosterone or other anabolic steroids, it has become a popular choice for bodybuilders and athletes who are looking to increase their muscle mass without any of the risks associated with traditional anabolic steroids.

In a study done on the effects of Ostarine on lean muscle mass, researchers found that it could increase muscle mass drastically. After administering a daily 1mg dose of the compound to participants over a 16-week period, researchers found that they’d gained 2-3 lbs of lean muscle mass. Even after increasing their daily dose to 3mg, the participants still failed to show negative side effects.

This is great news for anyone wanting to build lean muscle. These results suggest that Ostarine could act as a replacement to real steroids without the nasty side effects like acne, testosterone suppression, gynecomastia, mood swings, or fat gain.

The only downside is that Ostarine’s effects are pretty minimal compared to other SARMS. However, thanks to its lack of side effects, it’s likely safer than more potent products. Nonetheless, MK-2866 is not something to take lightly. It most definitely works to enhance your performance in the gym.

Be warned, though, WADA has added it to its list of prohibited compounds, as some athletes have unfairly used it as a performance-enhancing drug.

Boost Fat Loss

Along with finding that Ostarine can help boost muscular generation, researchers have also found that it can help increase your standard metabolic rate.

If true, this means that Ostarine can help your body burn more calories at a resting state, promoting caloric deficit and initiating your body’s natural fat-burning response.

These findings have led many bodybuilders to embrace Ostarine as a thermogenic fat burner in their stacks.

Currently, though, there isn’t enough hard science to back up these claims. For us to give an accurate assessment, we’ll have to wait for the results of more research to come out before we can recommend taking Ostarine as an effective thermogenic fat burner.

Improve Insulin Resistance

There is a growing body of research pointing towards Ostarine working as an effective insulin regulator.

By increasing the body’s natural insulin resistance, Ostarine may help to keep blood sugar levels more consistent, preventing both high and low blood glucose levels. If proven, these findings would suggest that Ostarine could help better absorb nutrients and increase muscular recovery.

Furthermore, this would suggest that Ostarine has potential benefits as a treatment for Type II diabetes.

If it can help regulate blood insulin resistance, it could help stabilize diabetic blood glucose levels and act as a daily treatment against the disorder.

Ostarine effects

Ostarine Dosage Information

First of all, MK-2866 has been shown to be effective at very low dosages. I am talking dosages as small as 1mg to 3mg.

However, an average dosage would be between 10 and 30mg a day. There is no scientific evidence that these are better dosages. However, anecdotally these dosages gave more improvements like muscle mass, strength, and recovery.

We definitely wouldn’t advise anyone to go over the clinical dosage, which is 3mg. These dosages have been proven not to give you any adverse effects.

However, higher dosages could possibly mean more side effects. 

I personally liked to use ostarine at 10mg for at least 8 weeks while I was cutting down. It immensely helped me with muscle preservation and muscle hardening.

Ostarine dosage

The growing body of research surrounding Ostarine suggests that it’s highly effective even at very low doses. By low dosages, we’re talking as little as 1mg to 3mg a day.

This would make it one of the most effective SARMs at that amount, despite its classification as a ‘mild’ compound. Nonetheless, most bodybuilders take a larger dose of around 10mg to 30mg a day.

To be honest, though, there’s little research to back up how much you should take every day. Based solely on anecdotal evidence, many bodybuilders have reported that these higher dosages have helped them build muscle mass more quickly, as well as increasing their overall strength and shortening their recovery times.

Experienced users do not recommend going above 30mg a day because the higher the dosage, the more side effects you can experience. 

When searching for information about a typical cycle, you will see that it’s between 6-12 weeks and ranges from 10-30mg of ostarine a day.

We recommend using a Post Cycle Therapy (PCT) like Rebirth PCT by Huge Supplements to recover from the testosterone suppressive side effects and keep your new muscle gains, and also a cycle support supplement like Defend.


If you are planning to take Ostarine, you’ll need to understand how it works. By studying the half-life, you can space out your dosages to guarantee you are getting the maximum dosage at all times.

According to recent studies, Ostarine has a half-life of around 24-hours. This means that you can run a cycle by taking the appropriate dose just once a day.

If you are willing to start an Ostarine cycle, we recommend taking it at the same time every day with your other supplements.

No matter if you take it in the morning or in the evening, it will stay in your system throughout that 24-hour period, helping you to outperform your usual best.

Can you stack Ostarine?

Theoretically, you could stack Ostarine with a handful of other SARMS but, while it could be effective, it could also be incredibly dangerous.

Keep in mind that Ostarine is still relatively new and there’s not a lot of data out there on how it interacts with other compounds. If you start stacking it with other products, it could create a harmful interaction and cause harsh side effects.

If you are willing to play around with science, just be careful!

It’s always best to add new compounds one at a time and slowly increase your dosage until you are certain that it’s not causing harmful side effects.

Some of the more common stacks we’ve heard of include MK-2866 plus GW-501516, S4-Andarine, or MK-677. These compounds are all SARMs that have been shown to produce similar effects.

One last thing that we should point out before moving on—increasing your dosage sizes could lead to a higher chance of liver toxicity. If you start to experience any of the following symptoms, stop taking the products and consult a physician:

  • Jaundice (yellowing of the skin or eyes)
  • Dark Urine
  • Widespread Itchiness
  • Pain in the upper right side of your abdomen
  • Unexplainable Flu-like Symptoms

If you decide to stack SARMs, we advise taking cycle support to help protect your vital organs such as a liver support supplement.

Does Ostarine have Side-Effects?

Research and anecdotal reports have both shown that MK-2866 usually doesn’t cause any adverse side effects.

That being said, though, a select few studies have suggested that taking Ostarine for an extended period could lead to some serious health issues. One such study found that long-term Ostarine usage can lead to acute liver injury.

Other commonly reported symptoms related to Ostarine usage include:

  • Headache 
  • Back Pain
  • High Blood Pressure
  • Suppress testosterone
  • Liver Injury

It’s hard to say with 100% accuracy what the exact range of side effects are but scientists and medical researchers are actively investigating how long-term Ostarine usage can impact the body.

That being said, though, one of the most widely accepted side effects of taking a SARM is testosterone suppression.

It is believed that SARMs suppress testosterone production by binding to androgen receptors in the body, which interferes with the production of testosterone. When this happens, your body will start to undergo changes, including reduced muscle mass, loss of bone density, and changes in sexual function.

If this happens, you will need to take Post Cycle Therapy or SARMS PCT to restore your body’s natural testosterone levels as soon as possible. We recommend using a PCT supplement like Rebirth PCT by Huge Supplements to recover from the effects of testosterone suppression and keep your new muscle gains.

There are multiple signs that Ostarine is liver and kidney toxic; if you would like to be safe you should always run on-cycle support.

The only other side effects that you may experience include liver toxicity, which we’ve covered above in the previous section.

Overall, we wouldn’t recommend taking Ostarine for more than a few months, since the long-term effects are still under investigation and similar SARMs have been shown to cause some harmful symptoms.

Instead, consider taking something healthier, such as Ecdysterone by Huge Supplements.

This is a natural product that’s way safer than any research compound, such as Ostarine. It’s made from organic products and has been thoroughly researched to show that it doesn’t cause adverse effects.

Does Ostarine Cause suppression?

Ostarine does suppress your natural hormone levels. While it’s not as suppressive as other SARMs such as RAD-140 or LGD-4033, it most definitively suppresses your natural testosterone.

Even at low dosages of 10mg per day, there will be a decrease in natural test production. Anecdotal experiences have shown us that the higher the dosage, the more suppression will occur.

That means you will need a post cycle therapy supplement; we advise going with Rebirth PCT. It’s the best PCT supplement for SARMs and can be ordered online.

You need to run Rebirth for a minimum of 4 weeks and a maximum of 8 weeks, depending on how you feel.

No matter what anybody tells you, Ostarine is suppressive and requires a post cycle therapy.

Where Can You Buy Ostarine?

We get a lot of users asking where to buy a sample of Ostarine but, truth be told, we don’t really advise that you use SARMs.

They’re not well enough researched to take safely and could lead to some nasty side effects such as liver toxicity and testosterone suppression. Even the FDA has issued warnings against these products, as they remain within the boundaries of a research chemical.

Nonetheless, if you are absolutely dead set on purchasing some Ostarine, we recommend sticking with verified and trusted sources.

There are a handful of authentic labs throughout the U.S. that have made it their duty to create clean supplements for bodybuilders willing to work outside the bounds of the FDA’s recommendations. For the best suppliers, we recommend either Chemyo or Sports Technology Labs. You can buy Ostarine by clicking here.

Their products are properly tested and proven to contain Ostarine. This way, you can be 100% sure that what you are getting is the real deal. Just remember that this compound is still being researched and that human trials still need to be conducted on a larger scale.

For now, it’s nearly impossible to say for sure what to expect from MK-2866 in the long term so just proceed with caution.

If you are dedicated to building strong and lean muscle mass, though, don’t worry. We have just the product you need to get the gains you are after without putting your health and body at risk.

Check out a few of our top recommendations in the next section and give them a try today. Many people have asked us where to buy ostarine. But the truth is, we advise against the use of  SARMs because of their unknown safety profile.

Ostarine Alternatives

For a safer alternative to Ostarine, we recommend checking out Ecdysterone, sold by Huge Supplements. As you can probably guess from its name, Ecdysterone contains ecdysterone, an all-natural steroidal that’s incredibly potent and helps generate lean muscle mass without the harmful side effects of a SARM.

Ecdysterone is a steroidal hormone found in insects. It is a precursor to molting hormones and has been found to increase the lifespan of fruit flies and C. elegans (a type of roundworm).

Scientists currently believe that ecdysterone works by activating the transcription factor, nuclear receptor subfamily 3, group C, member 1 (NR3C1), which is also known as the glucocorticoid receptor.

Ostarine Alternative

Ecdysterone has been shown to increase the expression of genes involved in protein synthesis, including muscle-specific actin and myosin.

It has also been shown to increase the expression of genes involved in mitochondrial function and energy production, helping to boost endurance and performance in the gym.

Other than being an insect hormone, ecdysterone is also a naturally occurring phytochemical found in a variety of plants, including Rhaponticum carthamoides (a Russian plant used in traditional medicine).

As one of the leading sources for ecdysterone, Rhaponticum carthamoides has been shown to increase protein synthesis, muscle mass, and strength in animals.

If this sounds like something you’d be interested in trying, skip buying Ostarine and go for something both healthier and more natural. We’ve been able to gain nearly 8lbs a week by adding ecdysterone to our stacks and have already planned out our next cycle. Best of all? We did it all without taking a PCT.


Ostarine is a mild SARM known for its muscle-building and performing-enhancing effects. It has quickly become a popular SARM among bodybuilders to quickly build lean muscle mass and it’s reported to have only mild or no harmful side effects.

However, it’s currently still undergoing research, and that is why we don’t condone the use of it. We can’t guarantee that it’s safe to take.

Most bodybuilders take a daily dose of 10 to 30 milligrams over an 8 to 12-week period. During this time, some users have reported side effects, including testosterone suppression.

Therefore, any SARM cycle needs to be followed up with post-cycle therapy. Otherwise, you’ll put yourself at risk of losing the muscle you’ve gained and suffer hormonal imbalances.

As far as we’re concerned, though, you should avoid Ostarine and, instead, take something healthier and more natural, such as Ecdysterone.

Even if the side effects are minor, there’s not enough research to prove that it doesn’t cause long-term damage. Ecdysterone, on the other hand, is proven to be safe and effective.

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