YK-11
guinea pig
The Dose Guy’s verdictSep 1, 20262 sources
YK-11 is mislabeled. It is marketed as a SARM and a myostatin inhibitor, but it has a steroidal backbone, carries gyno risk, and the myostatin inhibition claim traces to one cell study. No human trial exists. Zero. The rat data that does exist shows hippocampal damage, not muscle growth. If you want a real SARM with real data, run ostarine. If you want serious mass, run an actual anabolic and own it. YK-11 sits in the gap between those options wearing a label it has not earned.
What it is
YK-11 has a steroid nucleus. That matters. It is not a nonsteroidal SARM the way ostarine and RAD-140 are. It acts as a partial agonist of the androgen receptor and, in one cell study, induced follistatin expression in myoblasts. Follistatin suppresses myostatin, which is the brake on muscle growth, and that finding is the entire basis for the “myostatin inhibitor” marketing. One cell line, one study, extrapolated into a selling point.
The steroidal structure puts gyno on the table in a way the nonsteroidal SARMs do not. The reports are consistent at standard doses. The mechanism behind it is not established. It is also chemically unstable, hydrolyzing within hours in lab conditions, which raises real questions about what reaches your androgen receptors from a capsule that has been sitting on a shelf.
What the research shows
The evidence base is cell studies and rat data, and the rat data is not encouraging:
Realistic protocols
I am not writing a confident protocol for a steroidal compound with zero human data and rat studies showing brain inflammation. For the record, the community runs YK-11 at 5 to 10 mg a day, orally, for six to eight weeks, sometimes stacked with LGD-4033 or RAD-140 in a mass cycle. PCT afterward is standard, because the suppression is real and may be heavier than people expect from something sold as a SARM.
YK-11 is WADA-banned. If you compete in a tested sport, this is a positive test.
A third-party COA matters double here. YK-11 hydrolyzed within hours during lab validation for supplement screening, and a survey of 60 dietary supplements found products containing YK-11 that was not disclosed on the label. The compound degrades fast and the market mislabels it. Both problems at once.
If you run it anyway: start at 5 mg, keep the cycle to six weeks, get bloodwork before and after covering hormones, lipids, and liver, and watch for gyno signs. You are the experiment.
Side effects
The steroidal structure brings sides that nonsteroidal SARMs do not:
