Ostarine what is it? Is it a Steroid or Not?

Scientists initially hypothesized that, unlike typical steroids, SARMs would be able to target specific tissues, such as the muscles or bones. In theory, this was supposed to limit their side effects.

Sarms have surfaced as a performance enhancer without the side effects of Steroids use.

Many bodybuilders and athletes swear by Ostarine and claim it offers significant muscle mass and performance gains with few risks.

Ostarine is being researched for its ability to improve serious muscle wasting diseases. It may be approved for clinical use if the trials attest to its favorable benefits/risks ratio.

Ostarine is a selective androgen receptor modulator (SARM) touted to boost muscle mass. 

Key Components:

  • Increases lean muscle mass and strength
  • Shouldn’t cause hormonal imbalance
  • May improve bone strength
  • May lower cholesterol and improve insulin resistance


SARMs are hypothesized to target muscles and increase anabolic processes while sparing the reproductive organs. Among many synthesized SARMs, the structure of Ostarine seems to offer some potential “advantages.”

It’s no secret that androgens increase skeletal muscle mass – that’s the main reason why men typically have more muscles than women. The activity of androgens in the body goes well beyond muscle-building, though. When sensors for androgens are non-selectively stimulated by drugs like steroids, it usually results in a long list of side effects.

In one study on mice, Ostarine was as effective as the most influential androgen, dihydrotestosterone, at restoring the size of pelvic floor muscles. Muscles in the pelvic floor are especially rich in androgen receptors (AR) 

Ostarine could also activate muscle stem cells (satellite cells), which help remodel and regenerate muscles. Surprisingly, it turned out that Ostarine also stimulates cells in the connective tissue, which are important for a successful recovery from muscle injuries.

Ostarine increased the activity of the insulin-like growth factor 1 gene (IGF-1), which boosts muscle growth and strength.

However, we can’t make any conclusions based on data from cellular studies. Many drugs show some “promise” at the cellular level, only to be abandoned due to a lack of efficacy or risk of toxicity in later animal or human studies.

Although Ostarine is believed to target androgen receptors in muscles while sparing reproductive organs, no data backs this hypothesis up. Clinical studies are lacking.

Potential Uses of Ostarine

This section focuses on the clinical and scientific research that has been done on Ostarine so far.


1) Muscle Mass

Ostarine is being researched for reversing muscle loss in cancer patients, people with muscular dystrophy, and the aging population.

In a clinical trial of 120 healthy elderly people, enobosarm increased lean muscle mass and fitness. Only those who received 3 mg of enobosarm daily for 12 weeks saw benefits, while lower doses did not work as well. Importantly, its side effects were similar to placebo, with no steroid-like risks.

In another trial, enobosarm increased lean muscle mass in 159 cancer patients. Cancer patients who already started to lose muscle mass prior to the study gained about 2 – 3 lbs after taking enobosarm for about 4 months. The lower (1 mg/day) and the higher (3 mg/day) dose worked equally well.

Large clinical trials of enobosarm for preventing muscle loss in cancer patients are currently underway.

Ostarine may increase muscle mass and prevent muscle wasting in older people and cancer patients.

2) Bone Health

A decrease in bone-protective sex hormones with age increases the risk of poor bone health and osteoporosis. Increasing muscle mass can reduce the risk of bone fractures and speed up recovery, especially in older people .

Since Ostarine mimics testosterone in the muscles and bones, it has the potential to prevent bone diseases. Animal studies confirmed that SARMs like Ostarine could increase both muscle and bone strength. No human study has confirmed the benefits yet.

3) Heart Health

Ostarine may also be beneficial for people with heart disease, who often suffer from muscle wasting and weight loss.

Bulking Cycles

Users report:

  • Pure, clean, dry lean muscle gains (~6 – 8 lbs)
  • Milder gains than with steroids
  • Increased strength, stamina, and lifting endurance
  • No water retention
  • Great pumps during workouts
  • Increased energy and sense of well-being
  • No post-cycle crashes
  • No need for pre-cycle supplements
  • No need for liver-support supplements
  • No increases in aggression
  • Women report more obvious muscle gains and fat loss than men

Cutting & Fat Burning

Users report the following effects of Ostarine for cutting cycles:

  • The Big One: maintaining muscle mass
  • No strength loss
  • Fat loss

For all bodybuilders, the major downside to cutting cycles is muscle loss. That’s probably why so many love Ostarine – they say it prevents muscle breakdown but helps burn fat. This is probably the most talked-about aspect of Ostarine for body building.

Going back to the basics, it’s impossible to avoid being in caloric deficit if you want to burn fat and lose weight. However, your body will always interpret caloric deficit as a signal to break down all available energy stored in the body, including the proteins in your muscles.

Users report that Ostarine stalls this catabolic process, apparently stopping the body from using proteins as fuel but still helping to burn fats. Users say it helped them maintain muscles despite being on a low-calorie diet, keeping the anabolic processes going. They sometimes combine it with Cardarine to boost cardio endurance.

Ostarine is popular in bulking cycles but even more so in cutting cycles. Users say it stimulates fat burning and prevents muscle loss, but its actual effects and safety are unknown.

Body Recomposition

Used for recomping, Ostarine users reported:

  • Gaining muscles
  • Losing fat
  • Gaining some weight overall (depending on the diet and total number of calories consumed per day)


Users report:

  • Enhanced muscle recovery (at lower doses) after a week or two
  • Improved injury prevention
  • Better joint mobility
  • Healing of bone and tendon injuries

Coming off TRT

One user explained how taking only Ostarine allowed him to maintain muscle gains after coming off TRT (testosterone replacement therapy). He didn’t lose any weight and even reported increased strength. A rebound effect after TRT is common and muscle loss is one of the most feared downsides.

Bodybuilders report using Ostarine for recovery, body recomposition, and coming off TRT

Bodybuilding Dosage

The Ostarine-community seems to have established unofficial dosage guidelines based on “trial and error.” Bulking doses (3 – 8 weeks):

  • Most male bodybuilders use 25 mg/day
  • Women typically use up to 10 mg/day

Since Ostarine has a long half-life (24 h), most people take the daily amount all in one shot. Some still split the daily dose into 2-3 chunks.

The same users report cutting doses (4 – 8 weeks) or for injury prevention:

  • Men: 15 – 20 mg/day
  • Women: not mentioned, but the men dose is usually halved

Body recomposition (4-8 weeks)

  • The dose ranges between 12.5 – 25 mg/day

Some users reported taking Ostarine alone (especially for bulking cycles) while others combine it with other SARMs and slightly lower its dose.

Cycles & Time Off

Ostarine is commonly cycled for up to 12 weeks. Users who stopped cycles at the 8-week mark experienced fewer side effects. While some users don’t experience any side effects even with cycles lasting over 12 weeks, the chances undoubtedly increase.

As a general rule among experienced bodybuilders, time off should equal the duration of the cycle. As an example, this would mean taking a 12-week break from ostarine after cycling it for 12 weeks and using PCT for 3-4 weeks. The time off is usually counted after PCT.

Some think that the strict time on=time off rule should be abandoned for more personalized strategies. Proponents of shortening the time off recommend ordering detailed lab tests after the cycle + PCT to assess overall hormone levels and any potential problems.

If everything is alright, some restart Ostarine cycles soon after (1-week breaks). However, if the labs point to health problems, delaying Ostarine or any other bodybuilding supplements is a must for all sensible users.

Ostarine is a dangerous drug. Speak with your doctor about safer alternatives.

We advise speaking to a doctor before taking any drug, especially an unscheduled drug with limited long-term safety data in humans.

Ostarine Side Effects and Cautions

Clinical Data

As mentioned, the World Anti-Doping Agency banned SARMs as they can increase physical fitness and stamina.

In limited studies, Ostarine was well tolerated and posed an insignificant risk of drug interactions with commonly used medication (antibiotics, antifungals, statins, and Celebrex). However, the existing studies did not focus on Ostarine’s side effect profile. Larger, better-designed studies are needed.


With the goal of minimizing estrogens and the detrimental effects on testosterone short- and long-term, most bodybuilders start PCT right after an Ostarine cycle. PCT (Post-Cycle Therapy) consists of anti-estrogens (like Clomid, Nolvadex), which are usually taken for 3-4 weeks.

Users who are more sensitive to estrogen or those using high doses (35 mg/day) combine it with aromatase inhibitors (Anastrozole/Arimidex), which prevent the conversion of androgens to estrogen.

The opinions are mixed when it comes to PCT. Some don’t feel the need for it after Ostarine, especially with lower doses (approximately 10 mg/day). Others consider both anti-estrogens and aromatase inhibitors a must after Ostarine cycles. Users who check their labs and see increased estrogens start aromatase inhibitors during a cycle.



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