Andarine (S4) counterfeits: what lab tests of market products show
Andarine, known by the code S4, is one of the better-known selective androgen receptor modulators sold online. Independent laboratory testing of such products paints a troubling picture: frequent mislabelling, wrong ingredients and contamination. This editorial overview examines what the testing shows and why the unregulated market is so hazardous.
What Andarine (S4) is
Andarine is a non-steroidal selective androgen receptor modulator developed in pharmaceutical research. Like other SARMs, it was designed to act on androgen receptors with some tissue selectivity, with the hope of building muscle and bone while sparing other tissues. It never completed clinical development and is not an approved medicine anywhere.
Andarine is particularly associated with a distinctive reported side effect: visual disturbance, notably a yellowish tint to vision and difficulty adjusting to darkness, attributed to the compound's interaction with the eye. This unusual effect is one reason it fell out of favour even among the research-chemical community, though it remains widely sold.
Because it is an unapproved research chemical, Andarine cannot lawfully be sold for human consumption in the UK, and products marketed as S4 fall outside medicines regulation. This lack of oversight is precisely what makes independent laboratory testing of these products so revealing and so important.
This article does not describe how to use Andarine. Its focus is what analytical testing shows about the products sold under its name, and what that implies for anyone considering them.
Why laboratories tested the market
Because SARMs are sold outside the medicines system, there is no requirement that a product contains what its label claims, in the stated amount, free of contaminants. Academic researchers, anti-doping scientists and regulators have therefore purchased products marketed as SARMs and analysed them, to see what consumers are actually getting.
The most-cited study of this kind, published in a major medical journal, analysed dozens of products sold online as SARMs. It is representative of a wider body of work by anti-doping laboratories and regulatory agencies that have all reached similar, unflattering conclusions about product quality.
The motivation for this testing is partly consumer safety and partly anti-doping: athletes have failed drug tests after taking contaminated supplements, and understanding what is really in these products helps explain and sometimes defend such cases. The testing therefore serves both scientific and practical purposes.
Crucially, these analyses use rigorous methods — chromatography and mass spectrometry — that can identify and quantify the actual contents of a product with precision. Their findings are not anecdote but hard laboratory data about what is being sold.
What the testing revealed
The consistent finding across these studies is that a large proportion of products do not match their labels. In the most-cited analysis, only a minority of products contained the labelled compound at the stated amount. Many contained a different amount than claimed, some contained a completely different active substance, some contained unapproved drugs not mentioned on the label, and a number contained no active compound at all.
For a product specifically sold as Andarine (S4), this means a buyer cannot be confident it contains Andarine, that the dose is as stated, or that it is free of other substances. A capsule labelled S4 might contain another SARM, a different drug entirely, an under- or over-dose, or essentially nothing of pharmacological value.
| Discrepancy | What it means for the buyer |
|---|---|
| Wrong amount of active | Unpredictable, possibly unsafe exposure |
| Different active substance | Taking an unknown drug unknowingly |
| Unapproved drug present | Hidden ingredient, hidden risk |
| No active detected | Paying for an inert product |
| Contaminants | Impurities of unknown toxicity |
These findings are not isolated. Regulatory bodies including the MHRA in the UK and equivalents elsewhere, along with anti-doping organisations, have repeatedly warned that products in this market are frequently mislabelled and may contain undeclared pharmacologically active substances. The pattern is remarkably consistent.
The implication is stark: with such products, the label is not a reliable guide to the contents. Whatever risks Andarine itself may carry are compounded by the near-certainty that the product may not even be what it claims to be.
The risks of counterfeits and mislabelling
The dangers of this unreliability are several. First, dose unpredictability: a product with far more active than labelled exposes the user to higher-than-expected effects and risks, while one with less wastes money and may prompt the user to take more. Neither is safe.
Second, hidden ingredients: a product containing an undeclared drug exposes the user to the risks of a substance they did not knowingly take, including possible interactions with their medicines or health conditions. This is a particular danger for anyone with an underlying condition.
- Unknown exposure: real contents and dose cannot be verified.
- Hidden actives: undeclared drugs with their own risks.
- Contaminants: impurities of unknown identity and toxicity.
- Failed drug tests: athletes sanctioned from contaminated products.
Third, for athletes, the anti-doping consequences are severe. SARMs and many of the substances found as contaminants are prohibited in sport, and a positive test from a mislabelled product can end a career. Anti-doping bodies consistently warn athletes that they are responsible for what is in their bodies, regardless of a product's label.
Fourth, there is simply no accountability. In the regulated medicines system, a product that fails quality standards can be recalled and the manufacturer held responsible. In the grey market of research chemicals, there is no such recourse, and the buyer bears all the risk.
Legal status and the bigger picture
In the UK, Andarine and other SARMs are not licensed medicines and cannot lawfully be sold for human consumption. The MHRA has specifically warned against products marketed as bodybuilding aids that contain unlicensed active substances, noting both the legal position and the health risks. Buying such products also means engaging with an unregulated supply chain.
The laboratory testing of the market is, in a sense, a public service: it exposes the gap between what is advertised and what is delivered. The lesson generalises beyond Andarine to the entire SARM and research-chemical category, where the same problems of mislabelling and contamination recur across independent analyses.
For anyone with a genuine health goal — building muscle, improving body composition, addressing a hormonal concern — the unregulated market is a poor and risky route. Legitimate, monitored options exist for medical conditions, and for fitness goals the fundamentals of training and nutrition have far better evidence and no counterfeiting risk.
The overarching message from the testing is one of caution bordering on avoidance. When a product cannot be trusted to contain what it claims, no amount of research into the named compound's pharmacology can make its use informed, because the user does not actually know what they are taking.
Conclusions of the editorial team
Laboratory testing of products sold as Andarine (S4) and other SARMs delivers a consistent verdict: labels are frequently wrong. Products may contain the wrong dose, a different active substance, undeclared drugs, contaminants, or nothing of value. The label simply cannot be trusted as a guide to the contents.
This unreliability compounds whatever risks the named compound carries, exposes buyers to hidden ingredients and contaminants, and has cost athletes their careers through failed drug tests. In an unregulated market there is no accountability and the buyer bears all the risk.
Our related material on why supplement contamination is so common, on the broader SARM class and its evidence, and on protecting yourself from failed drug tests develops these themes further.
References
- Van Wagoner RM, Eichner A, Bhasin S, et al. Chemical composition and labeling of substances marketed as selective androgen receptor modulators. JAMA. 2017;318(20):2004–2010.
- Geyer H, Parr MK, Koehler K, et al. Nutritional supplements cross-contaminated and faked with doping substances. J Mass Spectrom. 2008;43(7):892–902.
- Gao W, Dalton JT. Expanding the therapeutic use of androgens via selective androgen receptor modulators. Drug Discov Today. 2007;12(5-6):241–248.
- Medicines and Healthcare products Regulatory Agency. Warning on unlicensed SARMs sold as bodybuilding products. London: MHRA; 2021.
- World Anti-Doping Agency. The 2024 Prohibited List, International Standard. Montreal: WADA; 2024.
- Efimenko IV, Valancy D, Dubin JM, et al. Adverse effects and potential benefits among SARM users. Int J Impot Res. 2022;34(7):699–705.
