Are Ostarine Side Effects Real & Should You Worry?

You’re working hard in the gym. You watch your calories and never miss a meal, but you can’t seem to match the progress of the other gym rats around you. Why is everyone so shredded and ripped, and you’re struggling?

SARMs are revolutionary compounds that give you the results you desire in the gym and the mirror. Ostarine, otherwise known as “Enobosarm” or “MK-2866” or “GTx-024,” is one of the first SARM compounds to gain popularity with bodybuilders, strength athletes, and fitness competitors.

If you’re thinking about running a cycle of Ostarine and new to SARMs, you might find you have mixed feelings about popping to top on the bottle. That’s okay. Many newbies are apprehensive about introducing chemicals to their physiology.

This article will discuss various Ostarine side effects that you might encounter while cycling. Knowing what to look out for will help you avoid potentially harming your body from using SARMs irresponsibly.

What you need to know
  • Ostarine, also known as MK-2866, is a selective androgen receptor modulator (SARM) that has been linked to several side effects.
  • Some of the reported side effects of ostarine include testosterone suppression, mood swings, nausea, and headaches. Less than 20% of our polled users reported any side effects.
  • Ostarine has also been associated with liver toxicity and an increased risk of cardiovascular events, although more research is needed to fully understand these potential side effects.

Understanding the potential side effects of MK 2866


Newcomers to SARMs are eager for gains. At the same time, you might have some concerns about the possible side effects of using Ostarine. Most of us know that steroids cause some heavy side effects, and no one wants to grow a pair of breasts when planning on developing rock-hard pecs instead.

Do SARMs create the same side effects as real steroids like testosterone and trenbolone? Feeling nervous about using SARMs is understandable. Fortunately, we have good news. The key to a successful SARMs cycle is education.

Knowledge is power, and by understanding how SARMS like Ostarine work in your body, you relieve the stress and worry about using these products. In this post, we’ll unpack everything you need to know about the side effects involved with your first Ostarine cycle.

Not sure which SARM is for you? Take the quiz on our homepage to get matched with the best right compound for your research.

Brief history of MK 2866

What is MK 2866?

Ostarine is a Selective Androgen Receptor Modulator (SARM). This compound is one of the original SARMs starting the evolution of anabolic compounds away from traditional products like testosterone.

GTx Inc. was the first lab to develop Ostarine, focusing on medical trails to treat conditions like osteoporosis and muscle wasting. The initial name of the compound, GTx-024, fell to the wayside with mainstream adoption, and most users prefer calling it by the name “Ostarine.”

Using Ostarine under the right dosage and conditions can help support lean muscle tissue growth and development. SARMs connect with androgen receptors in the body. They provide an enhanced effect on strength and endurance in the gym while supporting lean muscle tissue growth and burning body fat. Any novice bodybuilder knows that that’s the holy grail of training. When you gain muscle and burn body fat simultaneously, you’re essentially cheating the game.

A single cycle of Ostarine produces pronounced physical changes in the user. However, it does so without using the same biological pathways as traditional anabolics. MK-2866 is one of the “milder” SARMs available, and the technology around these compounds continues to evolve.

To understand Ostarine’s effects on your physiology, we need to explore some basics around how these compounds and other anabolics work in the body.

Is Ostarine a steroid like testosterone or trenbolone?

Ostarine = Steroid?

As mentioned, Ostarine is not steroids. Anabolic compounds (1) like testosterone, Tren, Anavar, and Winstrol all work with pathways in the body similar to those used by SARMs but produce a different effect. The distinguishing difference between steroids and SARMs is its effect on your hormonal system.

Hormones govern our thoughts, action, and behavior. An androgen is a hormone responsible for producing male characteristics, such as a deepened voice, facial hair growth, and muscle growth. When you introduce steroids to your body, it creates a massive androgenic response, flooding your tissues with androgens, which bind to receptors.

Androgens also convert to the hormone dihydrotestosterone (DHT), which binds to receptors. Finally, androgens convert to estrogen (estradiol), binding to your estrogen receptors. This androgenic response is responsible for many of the side-effects experienced by steroid users.

High levels of androgens lead to fast muscle growth, but it also results in many unwanted sides. Male pattern baldness is common with high doses, and gynecomastia occurs due to DHT’s aromatizing effect and increases in estrogen levels.  

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Other dangerous side effects attributed to anabolic use include elevations in LDL lipid profiles, increasing heart disease risk. Steroid use may also cause the growth of prostate tissue and cause enlargement of the heart’s left ventricle, compromising the cardiovascular system.

The shutdown of the Hypothalamic Pituitary Testicular Axis (HPTA) is the most significant effect of administering anabolic compounds like steroids. The HPTA governs the production of testosterone and critical hormones like LH (Luteinizing Hormone).

When introducing exogenous hormones to the body, it results in the shutdown of your natural testosterone production. During this “Shutdown” period, the body realizes it no longer has to create testosterone and turns off the tap.

However, when the user comes off the cycle, they are no longer receiving exogenous hormones, nor is their body producing any. It’s at this stage that users need to start a post-cycle therapy (PCT) to restart the HPTA. Failing to use the correct PCT results in a longer “recovery” period, resulting in loos of your gains and low mood as your hormonal system recovers.

For this reason, newbies should limit cycles to no more than 10-weeks, or they risk a delayed recovery that could have permanent consequences.

How does Ostarine work in the body?

Main Effects

SARMs don’t operate with the same biological mechanism (2) as traditional anabolics like testosterone. For decades, talented researchers wanted to produce a drug offering all the benefits of conventional steroids, without the unwanted side effects. SARMs are supposedly the answer to that problem.

SARMs are non-steroidal compounds designed to focus on the androgen receptor only. The claim is that you get the androgenic effect of anabolics without the aromatize and estrogen issues that cause most of the steroid sides.

The 5a-reductase enzyme (3) responsible for converting androgens into DHT doesn’t experience activation with SARMs. Therefore, you avoid many of the unwanted sides experienced with steroid use. Finally, SARMs have less of an effect on the central nervous system and the HPTA, reducing the impact of HPTA shutdown.

What are the potential side effects of running a cycle of MK 2866?

Side Effects

While the science says that SARMs are less harmful to your hormonal system that traditional steroids, there are still risks involved with taking Ostarine. MK-2866 does produce some shutdown effect (4), suppressing your natural production of testosterone.

It’s for this reason that a PCT is necessary after using a cycle of Ostarine. However, it’s important to note that your recovery will be far faster than with anabolics. Ostarine doesn’t shutdown the HPTS entirely. Therefore, it’s easier for you to get things back online after your cycle, without using PCT drugs like Nolvadex and Clomid.

A PCT with Ostarine can involve natural test-boosting products to strengthen the HPTA after your cycle. However, most users hardly report any sides with Ostarine use. Some users who start with high doses might encounter some initial problems that fade away as you adjust your intake.

Almost all these sides result from an increase in water retention in the body in the first few weeks of using Ostarine.

  • Headache
  • Back Pain
  • High Blood Pressure

These are the most common side effects of using Ostarine, and they’ll dissipate as you adjust your dose, and your body acclimatizes to the compound.

Conclusion and FAQ about Ostarine’s side effects

Wrapping Up

Ostarine is not a steroid; it’s a SARM. You won’t experience the same sides as steroids due to the drug’s unique mechanism of action in your body. If traditional anabolics are a shotgun of androgens to your body, think of Ostarine as a sniper.

You get a targeted dose directly where you need it, without the fallout from adverse effects on the hormonal system or CNS. While Ostarine is not entirely free from side effects, they are easy to control, fade fast, and less dangerous than those caused by anabolics.

What Ostarine dosage is good for minimum side effects?

Novice users can start with a dose of 10mg to 15mg. Increase the dose weekly until you begin experiencing sides, then back off by 5mg to find the sweet spot. For best results, split your dose into the morning and evening, and don’t use more than 35mg a day.

Can I take Ostarine year-round?

No, you need to cycle Ostarine in 6 to 8-weeks courses. Going on year-round diminishes the body’s response to the drug, and increases side effects.

Is Ostarine hard on my liver?

No, Ostarine is not a methylated compound and has no liver toxicity. Extended use of it, however, can be taxing on your body.

DISCLAIMER: The author and publishing website in no way endorse the use of SARMS. This content is for educational and research purposes only. The author and publishing website incur no liability for your use of SARMs or the information in this article.

Research Sources Cited:

Chris Jackson
Chris Jackson

Chris Jackson, co-founder of, is a renowned fitness blogger, physique model, and evolutionary bioscience researcher specializing in SARMs (Selective Androgen Receptor Modulators). His extensive work, characterized by cutting-edge research and practical training advice, has made a leading source for accurate, credible information on performance enhancers. With a dedication to improving the understanding and application of SARMs in optimizing human performance, his contributions have not only expanded public awareness but also shaped the conversation around these substances. Chris's pursuit of knowledge and commitment to sharing it continue to inspire many in their fitness journeys.

  1. I’m a first time user of SARMs and took 20mg of Ostarine for 4 weeks. I’ve experienced a considerable testosterone suppression, going from 500 to 180.

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