YK11 Stacks: 4 Common Combinations and What Is Known

Short answer: the four YK11 stacks people talk about most are YK11 + MK-677 (bulking), YK11 + cardarine (cutting), YK11 + SR9009 (recomp) and YK11 + ostarine. None of them has ever been studied: YK11 itself has no human trials, so every dose and result for these stacks comes from user reports. What is known is what each partner compound does on its own, and that is what this page sets out.

What is YK11

YK11 is a synthetic steroid that acts as a partial agonist of the androgen receptor, which is why it is sold as a SARM (Kanno 2011). Its “myostatin inhibitor” label comes from one cell study: in mouse muscle cells it raised follistatin, a myostatin-blocking protein (Kanno 2013). In rats, five weeks of YK11 caused oxidative stress and inflammation in the brain (Dahleh 2023). Its half-life and its effect on testosterone have never been measured. Full details: YK11 review.

Before You Start

Prior to diving head first into your YK11 stack, it’s important to consider the following three guidelines before starting.

1. Blood Work

It’s very important that you get blood work done before and after your cycle.

Your blood markers are the best indicator telling you what exactly is happening to your body while exposed to exogenous substances.

For a YK11 stack the useful markers are total and free testosterone, LH, FSH, a lipid panel and liver enzymes (ALT, AST, bilirubin); add fasting glucose with MK-677. The PCT and bloodwork planner lists them with timing.

2. Don’t Stack YK11 With Suppressive SARMs

I’ve seen some websites (and vendors) promoting stacks with YK11 containing very suppressive SARMs such as Ligandrol, Testolone or even S23.

The reason is measured suppression in the compounds that have been tested: LGD-4033 lowered total testosterone at just 1 mg a day in 21 days (Basaria 2013), and S-23 cut LH by more than half in rats within two weeks (Jones 2009). Adding YK11, whose effect on testosterone has never been measured, only adds unknowns. Even Ostarine lowered total testosterone at 1–3 mg a day (Dalton 2011).

3. PCT Is Non-Negotiable

Users almost always follow YK11 stacks with a SERM such as Clomid or Nolvadex, because they expect their own testosterone to be suppressed. With YK11 that has not been measured, so there is no research-based PCT for it. What studies show about the SERMs themselves is in Clomid PCT and Nolvadex PCT.

Four YK11 Stacks And Results You Can Expect

1. YK11 Bulking Stack (YK11 + MK677)

Evidence level: the doses in this table are what users commonly report (anecdotal). YK11 has never been tested in humans, so no stack with it has been studied. This describes reports; it is not a protocol.

What MK-677 is known to do: it is a growth hormone secretagogue, not a SARM. In a 12-month trial in older adults, 25 mg a day raised IGF-1 1.5-fold and added 1.1 kg of fat-free mass vs a loss on placebo, with more appetite (67% vs 36%) and higher fasting glucose (Nass 2008). Leg swelling from water retention was also more common than on placebo.

MK-677 is not a PCT. The old version of this page said it had been “proven” to act as one. In obese men it actually lowered total testosterone vs placebo over 8 weeks, without changing LH or FSH (Svensson 1999). A case report of LGD-4033 plus MK-677 found total testosterone down 62% after 5 weeks (Cardaci 2022). Read more in MK-677 as PCT and the MK-677 fact sheet.

Hair: claims that MK-677 protects hair follicles have no human evidence behind them.

2. YK11 Cutting Stack (YK11 + Cardarine)

Evidence level: the doses in this table are what users commonly report (anecdotal). YK11 has never been tested in humans, so no stack with it has been studied. This describes reports; it is not a protocol.

What cardarine is known to do: it is a PPAR-delta agonist, not a SARM. In human trials of 2–12 weeks it improved blood fats (triglycerides down 30% and LDL down 23% in 2 weeks at 10 mg a day) and raised fat burning after a meal, but no trial measured fat loss (Risérus 2008). Endurance gains have only been shown in mice. GSK stopped development after two-year rat and mouse studies found cancers in many organs (GSK letter, 2013).

Claims of losing 1% body fat a week on this stack are user reports. More: cardarine fact sheet.

3. YK11 Recomp Stack (YK11 + Stenabolic)

Evidence level: the doses in this table are what users commonly report (anecdotal). YK11 has never been tested in humans, so no stack with it has been studied. This describes reports; it is not a protocol.

What SR9009 is known to do: it activates REV-ERB, a body-clock protein. In the original mouse study it was injected twice a day and reduced fat mass in obese mice (Solt 2012); it has never been tested in people. Users split it into three doses because they believe it has a 4-hour half-life; no human half-life has been published. The advice to take it before 5 pm fits mouse data, where REV-ERB agonists increased wakefulness and cut REM and deep sleep (Banerjee 2014). A 2026 case report describes acute liver failure needing a transplant in a 17-year-old who had used SR9009 (Shams Bin Shaheen 2026). More: SR9009 dosage.

4. YK11 Shred Stack (YK11 + Ostarine)

Evidence level: the doses in this table are what users commonly report (anecdotal). YK11 has never been tested in humans, so no stack with it has been studied. This describes reports; it is not a protocol.

What ostarine is known to do: it is the most studied SARM.

The reported stack uses more than three times that dose, together with an untested compound.

The old claim of 14–16 lb of “pure muscle” in 8 weeks on this stack is hearsay; it is several times the 1.2–1.3 kg (about 3 lb) of lean mass measured in the LGD-4033 and ostarine trials. More: Ostarine stacks and YK11 vs RAD-140.

YK11 Stacks Side Effects

None of these side effects has been studied for YK11 in humans. The table shows the evidence behind each one:

Aggression

There is a very thin line between male dominance and aggression.

However, if you’re noticing that you’re getting into constant conflict with the people around you ever since you started your YK11 stack, it could very well be the compounds you’re using.

A bit of aggression is good; it’s even welcomed in the gym and needed to get a good pump going, but as mentioned, if you start seeing red everywhere you go, it might be time to start thinking about the negative consequences of your YK11 usage.

Hair Shedding

It’s not unusual to lose a bit of hair while on YK11; some people believe you’ll go bald, while others are saying there won’t be any hair loss.

From the author’s experience (kept from the original page), shedding stopped after the cycle. There is no study on YK11 and hair, so whether hair loss is common or permanent is not established. More: do SARMs cause hair loss.

Liver Toxicity

Increased Hunger

Increased appetite is the most common side effect of MK-677: 67% vs 36% on placebo in a 12-month trial, often easing within a few months (Nass 2008).

Wakefulness

Users report insomnia on Stenabolic. In mice, REV-ERB agonists increased wakefulness and reduced REM and slow-wave sleep (Banerjee 2014).

Where to Buy SARMs

No SARM, and none of the compounds on this page, is an approved medicine, so they are sold online as research chemicals. Quality is the main problem: in a JAMA test of 44 products sold as SARMs, only 52% contained a SARM and 41% matched the label; some contained other unapproved drugs instead (Van Wagoner 2017).

If you buy, choose a shop that publishes a third-party lab report (COA) for each batch. Our current pick is SwissChems; the reasons and what we checked are in the SwissChems review, and the general guide is where to buy SARMs.

Conclusion

YK11 stacks are built entirely on user reports: YK11 has never been tested in people, and no stack with it has been studied. The partner compounds are better known, and each brings its own documented issues: appetite, water retention and blood sugar with MK-677, cancer findings in animals with cardarine, untested human use and a liver-failure case with SR9009, and lower testosterone and HDL with ostarine. If you are new to this area, start by comparing compounds with human data in the SARMs database.