MK 2866 Ostarine Side Effects, Benefits & Dosage Review 2024

MK 2866 Ostarine Side Effects, Benefits & Dosage Review 2024

MK 2866 Ostarine Side Effects, Benefits & Dosage Review 2024


Ostarine is one of the best known SARMs and is used to increase lean body mass and improve physical function in bodybuilding. Ostarine benefits and side effects have been reported but are still not fully understood by all individuals starting a cycle. Here we look to unravel some of the facts and misconceptions around Ostarine so that it can be used successfully and without adverse effects.

What is ostarine?

Ostarine is one of the most popular SARMs on the market.


Ostarine (which is sometimes sold under other names such as MK-2866 or Enobosarm) is a selective androgen receptor modulator (SARM). SARMs are supplements designed to act specifically on androgen receptors, as the name suggests. The benefit of this being that effects will be exhibited in the places the user wants them - muscle and bone, with limited side effects on other parts of the body.

Ostarine is one of the most well-studied and most popular SARMs on the market. At this time, GTx (who have been developing the SARM) have conducted over 8 clinical trials on MK-2866 on about 600 hundred subjects. Since the early 2000s, the discoveries made about Ostarine have led to it being used in bodybuilding.

It is commonly recommended to first-time users for being milder and lower in side effects than other SARMs. If a woman were to look at going down the SARMs route, very low dose ostarine would be the smartest option.

What does ostarine do to the body?
Like all SARMs, Ostarine is a synthetic ligand which works by binding to androgen receptors (ARs) in the body. This means that, unlike anabolic steroids, its anabolic effects are tissue-selective. In binding to those receptors, ostarine can bring about accelerated muscle growth, enhanced athleticism and increased bone density.

Ostarine has been studied by the pharmaceutical company GTx, Inc. for uses including reversing osteoporosis and bone loss. It has the ability to help prevent muscle loss (Cachexia), muscle wasting, and overall dystrophy, conditions seen in cancer patients.

In athletic populations, such as in bodybuilders, these benefits have been taken into the context of gaining maximal skeletal muscle.

Ostarine can accelerate muscle growth & enhance athleticism 


What is Ostarine used for?
Outside of the research, ostarine is used as a performance/physique enhancing drug under a number of circumstances. Ostarine is incredibly versatile and can be stacked to support muscle building or weight loss goals. Ostarine is also great to help retain hard-earned muscle when in a harsh calorie deficit.

We will go into stacking options later in this guide!

Ostarine MK 2866 benefits & side effects

SARMs are considered to be milder, both in their positive and negative effects, to anabolic steroids or even prohormones. This means that the results (such as rate of muscle gain) will be less pronounced, but so should the degree of side effects. This is not to say that SARMs such as Ostarine are entirely without risk.

Ostarine benefits
The benefits of ostarine have been compared to anabolic steroids. Ostarine has a high oral bioavailability which makes it a preferable option to many who are not comfortable or confident self-injecting. Ostarine has shown the ability to increase muscle and decrease fat mass simultaneously (recomposition).

  • Increased lean muscle mass
  • Increased bone density
  • Apparent decreased body fat from improved body composition
  • Strength and performance gains
  • Improved recovery


Ostarine side effects & dangers

  • May negatively impact lipids (HDL and LDL levels)
  • Liver damage / toxicity
  • Suppression of natural testosterone levels
  • Increased estrogen conversion


To protect against potential negative outcomes, we would advise being as diligent with health support as you would be using a steroid or prohormone. Key areas of focus would be liver and cholesterol. Ingredients such as krill oil, CoQ10 and TUDCA would be a good start to your health stack! There are also a number of formulas on the market such as Med Kit which can tick many essential boxes.

Suppression of testosterone seems to become more apparent as higher doses of ostarine are used. Regardless, we would advise running a PCT between cycles if unable to access bloodwork that will confirm testosterone and estrogen status. The basis of this should be a natural testosterone booster such as Activate Xtreme, to kickstart your own endogenous production of testosterone. If estrogen related side effects are a concern, an aromatase inhibitor such as Alchemy can be added to the PCT stack.

Ostarine is still undergoing clinical trials so we do expect to learn more about it in coming years. As it stands, ostarine is Ostarine is considered an investigational drug that has not yet been approved by the US Food and Drug Administration (FDA) and is banned for use in tested sports by the World Anti-Doping Agency (WADA), so do keep this in mind if you are a competitive athlete.

Ostarine dosage: how much MK 2866 to take

Most brands will sell ostarine in 5-10mg capsules. For bulking, we'd advise starting with 20mg and for cutting, start at 10-15mg. Fusion Supplements MK-2866 can be used in a dosage of up to 30mg per day for advanced users. For women, 5mg a day is a good place to start.

Ostarine has a half-life of around 24 hours which means it can be taken once per day, without having to split the dose. For a first time user, this is another great benefit as there is less to remember! The exact timing doesn't matter too much, however it should be consistent. If you find it easiest to take with your vitamins in a morning for example, that is great!

If stacking, a lower dose can be used. When stacking SARMs, we'd always advise starting with the lowest recommended dose of each. Ostarine is incredibly versatile in how it can be stacked, meaning you're not short of options when looking for the best SARMs stack for you!

We'd advise running a SARMs cycle for up to 8 weeks followed by at least an equal amount of time off, during which a full PCT will be conducted.

Ostarine Stacks

Best Ostarine Cutting Stack:
Ostarine (10-20mg daily) can be stacked with Cardarine (10mg daily) for cutting. While the ostarine will help you not only maintain muscle, but build new muscle in a calorie deficit, cardarine will support endurance and keep training performance up on low food through a different mechanism to the SARM, being a PPARδ receptor agonist. For recomp (gaining muscle while simultaneously chasing fat loss), a low dose of Andarine can be added to support the anabolic effects of Ostarine.

Ostarine can be stacked with Cardarine for cutting.


Best Ostarine Bulking Stack:
If bulking, Ostarine (10mg-20mg daily) and Ligandrol (LGD-4033) (10mg daily) is an excellent stack. An optional addition would be MK-677 (25mg daily) which can be used to increase appetite if this becomes a limiting factor to the bulk. If utilising MK-677 we recommend learning more about that compound including the ideal MK-677 cycle length.


Ostarine & Ligandrol is an excellent stack for bulking along with MK-667.


Ostarine MK 2866 FAQs

How long does ostarine take to work?
With a half-life of around a day, Ostarine can start working within several hours. This means there wouldn’t be additional benefit to taking it pre-workout, unlike other oral supplements. By a couple of weeks into your cycle, the benefits of increased strength and better body composition should be very apparent.

What is the MK 2866 half life?
Ostarine has a half-life of about 24 hours (a full day). This means that, after taking a dose, about half of the amount would be in your system 24 hours later. This longer half-life means that one dose per day is sufficient, unlike other SARMs which might be better split.

Is ostarine safe to take?
As Ostarine has not yet been approved for use, much of the human data we have is annecdotal. Ostarine is considered safer than prohormones, but is not without side effects. We also cannot say for sure what the effects of long-term use are. Always research before starting a new supplement.

Is ostarine legal?
Ostarine is legal to buy and sell. It is however worth noting that Ostarine, and all SARMs, are considered research chemicals. This means that they have not yet been approved for human use at this time. Supplementing with Ostarine is banned in all tested sports by WADA.

Do I need a PCT for ostarine?
While some people would say Ostarine does not require PCT, we would still advise a post cycle therapy of over the counter supplements like a natural testosterone booster to be safe. The only way to know for sure if testosterone has been suppressed is with blood work (recommended).

Is ostarine the best SARM?
Ostarine might not be known for being the 'most potent' SARM, but it is the SARM we have the most study data on. For this reason, we would recommend it for first-time users. It is also useful in a variety of settings, from dieting to lean bulking.

Is MK 2866 a steroid?
MK-2866 is not a steroid. Anabolic–Androgenic steroids (AAS), are steroidal androgens wheras SARMs target specific receptors in muscle, fat and bone to illicit an enhanced response. MK-2866 is designed to act selectively on muscle tissue whereas AAS might have side effects on the entire body.

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