What is S4?
S4, also known as Andarine, is a non-steroidal selective androgen receptor modulator (SARM) designed to bind androgen receptors in muscle and bone tissue while minimizing androgenic activity in other organs. It is one of the milder SARMs in terms of overall side effect burden, making it a practical choice for cutting phases where the primary goals are muscle preservation, fat loss, and improved muscle definition rather than maximum mass accumulation. S4 is also one of the few SARMs associated with mood improvement rather than the mood suppression or aggression seen with more potent compounds in the class. Its main distinguishing side effect is temporary vision disturbances, specifically a yellow tint under certain lighting conditions, which resolves after discontinuation.
Mechanisms of Action
Selective androgen receptor binding in muscle and bone tissue, mimicking endogenous androgens like testosterone to stimulate anabolic gene expression, protein synthesis, and muscle fiber maintenance
Fat oxidation promotion via androgen receptor-mediated metabolic signaling that increases the utilization of stored fat as an energy substrate, contributing to improved body composition during a caloric deficit
Bone density support through androgen receptor activity in skeletal tissue, consistent with S4's original research context exploring treatments for osteoporosis and muscle wasting
Partial agonist activity at ocular androgen receptors which is responsible for the vision disturbance side effect, producing a temporary yellow tint in peripheral vision particularly in low-light conditions
Mild HPG axis suppression producing less testosterone suppression than more potent SARMs, though PCT is still warranted after a full cycle if not running a test base
Benefits
Muscle preservation and definition particularly effective during cuts where maintaining lean mass while reducing body fat is the priority, producing a harder and more defined physique over the cycle
Strength enhancement with users consistently reporting strength improvements that hold well even in a caloric deficit, making training more productive during cutting phases
Fat loss support through increased metabolic rate and preferential fat utilization, contributing to a leaner body composition without the muscle loss typical of aggressive cuts
Improved mood a meaningful differentiator from many other SARMs, with S4 associated with mood elevation rather than suppression or increased aggression
Bone density improvement suggested in research, offering a skeletal health benefit alongside the muscle and body composition effects
Mild and manageable side effect profile relative to more potent SARMs, making it a practical entry point or a useful addition to a stack without dramatically increasing side effect burden
Dosing
Use Case | Dose | Frequency |
|---|---|---|
Standard cycle | 25 mg | 3 times per day for 8 weeks |
Pre-workout boost | 50 mg | 45 minutes before training |
For a full cycle, 25 mg three times daily across an 8-week run is the standard approach. For users who want to use it more situationally, 50 mg taken 45 minutes before a workout delivers a noticeable pre-workout androgenic effect on its own. A test base is recommended during use and a proper PCT is required after the cycle if not already on testosterone replacement.
Warning: The vision disturbance side effect (yellow tint, particularly in low light or when transitioning between light and dark environments) is common at standard doses and should be expected. It is temporary and resolves after discontinuation. If vision changes become severe or disruptive, reduce the dose or discontinue use. Monitor liver enzymes, kidney values, and lipids throughout the cycle.
Safety Profile
Vision disturbances the most distinctive and commonly reported side effect, presenting as a yellow tint in peripheral vision especially in low-light conditions; temporary and resolves after stopping use
Mild testosterone suppression less pronounced than with more potent SARMs but still present, making PCT necessary after a full cycle without a test base
Dyslipidemia with S4 tending to raise LDL and lower HDL cholesterol, warranting lipid monitoring particularly on longer cycles
Liver and kidney stress with elevated liver and kidney values reported by some users, making blood work monitoring throughout the cycle advisable
Muscle cramps reported by some users, potentially linked to electrolyte shifts during use
Mild androgenic effects including possible acne or increased facial hair in some users, though significantly less pronounced than with traditional anabolic steroids
Citations
Jones, A., et al. Preclinical characterization of selective androgen receptor modulators. PubMed. https://pubmed.ncbi.nlm.nih.gov/20593435/
Disclaimer: The information provided is intended solely for educational purposes and should not be considered a replacement for professional medical advice. All compounds referenced are not for human consumption.
