Ostarine Gyno: Does MK-2866 Cause Gynecomastia?

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It was my third SARMs cycle and I remember I was terrified. “What's that?” I asked myself. It felt like my nipples were getting itchier each day, and I noticed swelling on one side.

I immediately ran to google and searched: “Does Ostarine cause gyno?” Sadly, I found out that under some circumstances, it can in fact, cause gyno (man boobs or gynecomastia).

The good news, is it's 100% fixable and preventable if you know how.

In this article, we'll cover:
  • What Causes Gyno?
  • Can Ostarine Cause Gyno?
  • How to Prevent Gyno
  • How to Reverse Gyno
  • …and more

So, if you're considering taking Ostarine or other SARMs, but want to be safe and are concerned you might get puffy nipples or gynecomastia, then keep reading.

What Causes Gynecomastia?

Before I explain the link between Ostarine MK 2866 and gynecomastia, you first need to have a basic understanding of testosterone, estrogen, and how hormones work in the human body.

Gynecomastia will start to pop up anytime your estrogen levels are way too high.

The reason for this is that the breast area and around the nipples have a very high concentration of estrogen receptors. That's why, when your estrogen levels are too high, gyno will be one of the first side effects you start to notice.

In short, gyno is really not a big deal and it's very easy to reverse and/or prevent entirely.

Can Ostarine Cause Gyno?

classifications of gyno

The short answer is yes, but the long answer is it depends entirely on your biology, your own testosterone levels and estrogen levels, your Ostarine dosage, and cycle length.

Technically, any selective androgen receptor modulator can lead to gyno, because SARMs increase free testosterone in the blood, which increases estrogen levels over time.

Again, it depends on the dosage, though. I didn't personally experience any negative sides until my third cycle of Ostarine, and that was because I did no on cycle support at all.

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After some research, I quickly found out that there's supplements and drugs you can take while on a SARMs cycle, to avoid any permanent nipple damage or man boobs.

In fact, there's even supplements you can take to reverse gyno, so if you already have a little bit of breast tissue growing and are worried, don't worry.

Thankfully, if you stick to the recommended dose, you will most likely not experience any sort of gyno from an Ostarine cycle. In fact, unless you take large doses, it's fairly rare to have.

In my experience, less than 5% of people get gyno from MK 2866.

That doesn't mean it isn't possible, though. A lot of it depends on your own unique biology, which will dictate how much testosterone suppression you get on cycle.

Preventing Ostarine Gyno

Like I said, most Ostarine users will not experience breast tissue growth, especially if they follow the protocols I recommend you do on cycle. Read my Ostarine dosage guide to find the safest dosage your body can handle, and don't take too much. That's first.

Here are some tips to avoid MK 2866 gyno:

  • Lower Your Body Fat – Gyno is simply excessive fat that's stored in the chest and nipple area. So, the easy solution to this, is to simply lose more fat.
  • Choose A Lower Dosage – This is by far the most important thing. Take a normal dosage, between 10-20mg/day of Ostarine, and you'll not only get great muscle gains, but the odds of you having a lump or developing gyno are very low
  • Choose A Shorter Cycle – Most of the people who end up getting problems with Ostarine went wrong by choosing too long of a cycle. Forget this 16 weeks and 12 weeks stuff. If you're prone to gyno, only do a max of 8 week cycles and pick a low dose.
  • On Cycle Support – This involves taking some type of anti aromatase drug, such as Arimidex or Arimistane, which will prevent testosterone from turning into estrogen, thus preventing gyno before it even begins.
  • Get Regular Blood Work – This is the #1 thing that nobody wants to do, but it's by far the most helpful to take a scientific approach if you want to reduce gyno. Again, gyno starts to happen when your estrogen levels are too high. Getting regular blood work to check on your hormones will let you catch the problem before it gets too bad

If you combine all of these tips, the odds of you getting any sort of side effects or issues from an Ostarine MK 2866 cycle are almost nothing.

But… what if you already have gyno?

How to Reverse Ostarine Gyno

testomax SARMs pct benefits

First off, if you have gyno and are taking Ostarine, stop taking it right now. You're at risk of making it worse and worse, and you want to do your next cycle right from the start.

Once you stop taking Ostarine for a couple weeks and your hormones get back to normal, the pain in your nipple and arm pit area should start to go away. Swelling should go down, too.

If you can't get rid of the gyno symptoms naturally, there's three other ways:

  1. Diet & Supplements – Anti-aromatase drugs are a wonder to behold when you start to develop some gyno. They're also a great way to protect yourself on cycle. I personally take 400mg of DIM every single day when I'm on cycle, for estrogen management.
  2. Drugs – Simply taking some Raloxifene or Nolvadex for 8-12 weeks has been clinically proven to drastically reduce gyno and can often entirely eliminate it.
  3. Surgery – This should be the last resort. Most people do not need to undergo surgery by a doctor to get rid of the gyno they're experiencing. This also costs upwards of $4,000 or more, whereas the drugs and supplements are under $100.

If you already have gyno and don't want to get surgery, your best bet is to run a cycle of Raloxifene for 8-12 weeks until the gyno disappears. 60mg/day will do the trick.


In summary, every dude wants to build muscle, shred body fat, and get super strong. Many of us take SARMs like Ostarine to do this, but are not aware of potential side effects.

Gyno is one of the more rare side effects for sure, but it's entirely possible that Ostarine MK 2866 and other SARMs can cause it if you aren't careful, and are prone to high estrogen.

Always be sure to take some type of anti-estrogen compound on cycle (like DIM or Arimidex), even if you don't think you need it. Once you get gyno, it's hard to get rid of, so it's better to just avoid getting it in the first place.

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LEGAL DISCLAIMER: The information on this page is intended for entertainment and information purposes only. It is not a substitute for professional medical advice. Always check your local jurisdiction’s laws before buying anything or doing anything. SARMs are strictly for research purposes only, and are not FDA approved to treat any condition.