Ostarine: Uses, Risks, Side Effects, Dosage and Where to Buy

Ostarine chemical structure diagram overlay with MK-2866 pills on table

Ostarine, or MK-2866, is a mild SARM that aids in bulking and cutting cycles to increase muscle mass and reduce fat. Many images are making the rounds showing the effects of Ostarine before and after.

This article will discuss the truth about Ostarine and its effects, including what it is, how it works, risks, side effects, alternatives, and the type of cycle results you can realistically expect.

What is Ostarine?

Ostarine, also known as MK-2866 and Enobasarm, is a class of selective androgen receptor modulator drugs (SARMs) that is mostly used by bodybuilders and athletes. Despite not having been approved by the FDA (US Food and Drug Administration), and it’s being illegal, it is still being used.

Ostarine was created specifically for the treatment of muscle wasting disorders, degenerative diseases, and osteoporosis. It was designed to maintain and even increase lean muscle mass in people who are unable to exercise or who live on a calorie deficit.

Ostarine  is also known as GTX024, as it was originally created by a manufacturer called GTx. Numerous studies have been done to verify the medical benefits of Ostarine.

Ostarine has been shown to reduce body fat and increase muscle mass. It also provides increased energy.

Additionally, research has shown that Ostarine can increase endurance, which allows you to push yourself harder in the gym for longer, more intense workouts. Ostarine has more recently been proven to preserve lean muscle mass.

Ostarine, unlike other SARMs, has undergone a substantial amount of human trials, and is considered safe in moderate doses. Phase II human trials involving Ostarine were completed in 2007.

However, it still has not passed all human trials and therefore cannot be sold or marketed under license.

What Are SARMS?

SARMs (selective androgen regulator modulators) are a class of drugs used for anabolic effects, including muscle growth, by stimulating androgen receptors. However, while steroids may provide similar effects as SARMs, some properties make SARMs the better option.

SARMs are not known to effect non-skeletal muscle tissue like steroids do. This means that the only parts of the body affected by the androgenic activity caused by SARMs is mainly muscle and bone tissue.

This makes it an extremely effective compound for increasing lean body mass. This is also why Ostarine is currently one of the most widely-used muscle enhancement drugs among athletes and bodybuilders.

How Does Ostarine Work?

The effects of any particular SARM will vary depending on how it works. Certain SARMs are anabolic in nature, while others use a different method of action.

Ostarine MK-2866 has an anabolic effect. As a result, side effects such as a testosterone suppression are possible when using this drug.

Ostarine binds to proteins in the body called androgen receptors. When Ostarine attaches to these receptors, it signals the muscles to grow.

However, unlike some other substances that attach to androgen receptors (like steroids), Ostarine doesn’t appear to cause as many side effects.


A number of health benefits have been associated with Ostarine. Some of these include:

  • Boosts lean muscle mass and strength (1)
  • Improves bone strength (2)
  • Increases IGF-1 levels (3)
  • Decreases cholesterol levels (4)
  • Improves insulin resistance (4)
  • Does not appear to cause hormonal imbalances (5)

Risks and Side Effects

Ostarine was tolerated well in limited studies and did not cause drug interactions with other commonly prescribed medications. The side effects profile of Ostarine were not addressed in the existing studies, however. More thorough research is necessary. (6)

Side effects reported in research trials include back pain and headaches. Ostarine’s long-term effects are not known. (7)

Currently, the available information concerning the side effects of Ostarine is extremely limited. The only research conducted has been limited to cancer patients due to the drug being a banned substance.

However, there is a fair amount of anecdotal data based on user reports posted in online forums and social media platforms. That said, the likelihood of experiencing side effects from Ostarine is relatively low.

Some of the less common side effects that users have reported include:

  • Testosterone suppression one month after cycle ended (no PCT).
  • Headaches
  • Elevated estrogen levels
  • Nausea
  • Pain in the testicles
  • Joint pain
  • Loss of strength
  • Difficulty achieving/maintaining an erection
  • Difficulty sleeping
  • Fatigue
  • Depression
  • Irregular menstrual cycle in women
  • Acne and other skin conditions
  • Increased hunger
  • Hair loss
  • Gynecomastia (although uncommon).

These reports suggest that Ostarine could cause similar side effects to steroid use.

How To Use Ostarine

The scientific research on Ostarine is very limited and has been studied only in the elderly and cancer patients. The effectiveness of Ostarine and its dangers have not been determined by any of the studies. The existing data suggests that Ostarine’s effects are not known and could potentially be harmful.

The following information was compiled using the feedback and reports from online communities. The information provided below is based only on anecdotal evidence and experiences provided by Ostarine users. It is not guaranteed to be accurate.

We don’t know if these experiences are affected in any way by other SARMs, drugs, or supplements taken along with Ostarine. Additionally, the actual composition or quality of Ostarine found in many products users purchase online is far from certain.

For Bodybuilding

Many bodybuilders report gains of 6-8 lbs. when they took approximately 25 mg per day during bulking cycles. Users often describe it as a ‘clean’ drug and claim that it increases lean, solid muscle mass and reduces fat with few side effects.

To maintain muscle gains, those who use steroids often take Ostarine for their PCT or between steroid cycles. Others who only use SARMs often still do PCT following an Ostarine cycle.

Users claim that the gains that Ostarine delivers are easier to maintain. Ostarine is said to offer benefits in all phases of bodybuilding, including bulking and cutting, as well as recovery and body recomposition.

Ostarine is also preferred by women as well because it seemingly doesn’t cause body hair growth, a deeper voice, or any other symptoms related to elevated androgens.

Ostarine is believed to give bodybuilders long-lasting pure muscle gains. However, we currently just don’t know how safe or effective Ostarine actually is.

Bulking Results

Some of the bodybuilding benefits that users report from the bulking phase include:

  • Solid, defined, lean muscle gains (6-8 lbs)
  • Gains less pronounced than with steroids.
  • Boost in strength, stamina and workout performance.
  • No water retention.
  • Excellent pumps while training.
  • Better mood and energy.
  • No post-cycle crash.
  • Pre-cycle supplements not necessary.
  • Liver-support supplements not needed.
  • No increase in aggressive behavior.
  • More noticeable muscle gains and fat loss in women.

Cutting Results

These users also report the following Ostarine fat-burning effects when used for cutting cycles:

  • Preserves lean muscle mass
  • No loss to strength levels.
  • Fat loss

The main drawback for bodybuilders when it comes to cutting cycles is the inevitable loss of muscle mass. Ostarine is so popular among bodybuilders because it helps to prevent muscle loss while still burning fat. This is the perhaps the most widely discussed aspect of Ostarine in bodybuilding circles.

Fundamentally speaking, if you want to lose weight and burn fat, it is impossible to avoid being in a caloric deficit. But your body will see a caloric deficit as an indication to start breaking down all the body’s available stored energy – this includes the proteins in your muscles.

Ostarine is said to halt the catabolic process. It stops the body using proteins for fuel, but still helps to burn fat. It’s claimed to have helped users maintain muscle mass, even with a low caloric intake. This allowed them to continue the anabolic process.

To increase cardio endurance, they sometimes cycle it with Cardarine (GW501516).

Although Ostarine is popular for bulking, it’s even more popular for cutting. But even though users claim it helps with fat loss and muscle preservation, the safety and effectiveness of Ostarine is not known.

Body Recomposition Results

Ostarine is also used for recomping, where users report:

  • Muscle growth
  • Fat loss
  • Weight gain (depending upon diet and daily caloric intake )
  • Recovery

Effects on Recovery

For post-workout recovery, users report the following:

  • Improved muscle recovery after 1-2 weeks (with lower doses).
  • Less prone to injury.
  • Greater joint motion.
  • Faster healing of injury to bones and tendons.

Dosage for Bodybuilding

Ostarine is not approved for human consumption because of the limited dosing data from clinical trials. There has been no safe or effective dosage established for this drug.

Nevertheless, Ostarine users appear to have established some general dosage guidelines, based on feedback and anecdotal data.

Dosage For Bulking (3-8 week cycle):

  • Men – 25 mg per day
  • Women – up to 10 mg per day
  • It is not known how many people have experienced serious adverse effects.

It should be noted that most men prefer bulking at a dose that’s almost 10 times higher than that used in patients with cancer. This is extremely concerning.

It can be very dangerous to megadose unapproved or under-researched chemicals. No one knows the potential consequences might be.

Ostarine has a 24-hour half-life, so most people will consume the entire daily dose at once. However, some people choose to divide the daily dose into two or three smaller doses.

Doses For Cutting (4-8 week cycle)

  • Men – 15-20 mg per day
  • Women – Unclear, but typically half the dose for men.

Dosage For Body Recomposition (4-6 week cycle)

  • Doses vary from 12.5 to 25 mg per day

Some users opt to take Ostarine alone, particularly when bulking. Others combine it with other SARMs and slightly decrease the dose.

The stacking together of multiple unapproved drugs is dangerous. The risk of harm is greater because the side effects and interactions of these drugs are not fully understood. Even more uncertain are the long-term consequences.

How to Cycle

Ostarine is often cycled for up to 12 weeks. Side effects were less common for those who stopped their cycles after 8 weeks.

Some users experience no side effects even after cycles last 12 weeks. However, the odds for adverse effects occurring no doubt increase with longer term use.

According to experienced bodybuilders, the time taken off should be equal to the length of the cycle. For example, you would take a 12-week rest from ostarine after having cycled it for 12 weeks . But first you’d need to do PCT for 3-4 weeks (the off-cycle time is generally begun after PCT).

However, there are those who believe that the time-on/time-off rule should be dropped in favor of more customized strategies. To shorten the time off, advocates recommend ordering lab tests after each cycle and PCT in order to determine overall hormone levels and identify any potential issues.

Some people restart Ostarine cycles after only a one-week break if everything is fine. All users should know that the use of Ostarine and any other bodybuilding supplements should be halted if the lab work indicates health problems.

Before taking any drug, we recommend speaking with a doctor.


Most bodybuilders begin PCT immediately after an Ostarine cycle in order to reduce estrogens and their adverse effects on testosterone, both short- and long-term. Post-Cycle Therapy (PCT) is a combination of anti-estrogens such as Clomid and Nolvadex, which are typically taken for 3-4 weeks.

There are differing opinions regarding the need for PCT. There are those who don’t believe it’s necessary after an Ostarine cycle, particularly if they are taking lower doses of around 10 mg per day. On the other hand, some people consider anti-estrogens as well as aromatase inhibitors mandatory after an Ostarine cycle.

Aromatase inhibitors are taken by users who have lab work done that detects an increase in estrogens.

Legal Ostarine Alternative

For those looking for a safe, legal alternative to Ostarine, but with no risk of side-effects, check out the supplement OSTA 2866 from CrazyBulk and OSTABULK by Brutal Force. Based on personal experience, both of these products deliver some of the most productive workouts of your life, increasing gains in lean muscle mass while also burning away unwanted fat.

OSTABULK and OSTA 2866 imitate the anabolic properties of Ostarine to trigger a quick increase in muscle size and strength. Their formulas contain powerful testosterone-boosting ingredients for better muscle composition and gains in muscle strength.

Intended to also rebuild muscle mass between workouts, these two products contain key nutrients that enhance muscle growth and boost bone strength and density. If you’re after quick gains in size and strength, then you might think about keeping these powerful anabolic supplements in regular rotation.

See Also: CrazyBulk Products Full Review and Brutal Force Full Product Line Review

Where to Buy Ostarine

Since there is so little clinical research on the safety of Ostarine, we can’t recommend it’s purchase. However, if you’re confident about your decision to research it you should only order from a trusted source.

SwissChems is our preferred vendor for those who wish to buy Ostarine. They are the best option because they maintain strict standards of quality. All of their products are regularly third-party-tested for purity, and the test results are available to view on their site.

Unfortunately, many online vendors do not perform regular testing and/or have inconsistent quality, and it’s not uncommon for the ingredients used to be ineffective or mislabeled. While we can’t recommend the purchase of SARMs, SwissChems is the safest choice for those who do.

Click here to buy Ostarine at the SwissChems website.


Despite lack of data on safety and efficacy, Ostarine is a potentially unsafe drug being used by bodybuilders and athletes. More extensive research is required in order to understand how Ostarine works, and whether it has potential uses for humans. It is not currently approved in any country.

Although Ostarine is often referred to by bodybuilders as safer than steroids, the whole idea that SARMs are selective and have fewer side effects has never been proved. It may be discovered that SARMs such as Ostarine end up being just as dangerous (or more-so) than steroids and other banned performance-enhancers.

We strongly suggest that you avoid using this drug. Instead, try an all-natural, safe and legal alternative to Ostarine.


  1. https://pubmed.ncbi.nlm.nih.gov/22031847/
  2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4083371/
  3. https://academic.oup.com/endo/article/156/12/4522/2422756
  4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3177038/
  5. https://pubmed.ncbi.nlm.nih.gov/19432422/
  6. https://pubmed.ncbi.nlm.nih.gov/27105861/
  7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3177038/
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