Andarine (S-4)
1 product from 1 brand · free UK delivery · EU 3–7 days
Andarine, also known as S-4, S4, GTx-007 and by its chemical name S-3-(4-acetylamino-phenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethyl-phenyl)-propionamide, is a non-steroidal selective androgen receptor modulator (SARM) of the aryl-propionamide family. It was one of the first SARMs to be characterised in detail in animals but never reached later-stage human trials. This page lists every brand of andarine stocked at Free Muscle, compared on strength per capsule, capsules per pack and batch testing, and summarises the published research and its limits.
What is andarine?
Andarine is a synthetic ligand of the androgen receptor (AR) built on the aryl-propionamide scaffold that also produced ostarine and S-23. The scaffold was derived from the anti-androgen bicalutamide by researchers at the University of Tennessee and Ohio State University, who found that small structural changes turned a receptor blocker into a tissue-selective agonist. Andarine behaves as a partial agonist in the prostate and a full agonist in skeletal muscle and bone in animal models, which is the defining SARM profile.
Unlike ostarine, andarine did not progress far in clinical development. GTx investigated it as GTx-007 for benign prostatic hyperplasia and muscle wasting in the mid-2000s, but no controlled human trial results have been published in the peer-reviewed literature and the compound was set aside in favour of ostarine. Andarine has never been approved as a medicine by the MHRA, EMA, FDA or any other regulator. It is widely discussed for a visual side effect, a yellow tint to vision and difficulty adapting to darkness, attributed to its nitro group, but this is reported anecdotally rather than in published trials.
What the published research reports
Muscle, bone and pituitary effects in castrated rats (2005). Gao and colleagues treated castrated male rats with S-4, dihydrotestosterone (DHT) or vehicle for eight weeks. S-4 restored soleus muscle mass and strength and levator ani muscle mass to the levels seen in intact animals, matching DHT. Where DHT more than doubled prostate and seminal vesicle weights relative to intact controls, S-4 returned them to only 16 and 17 per cent of control. S-4 also increased total body bone mineral density more than DHT and suppressed plasma LH and FSH in a dose-dependent manner, indicating agonist activity in the pituitary.
Bone loss and body fat in ovariectomised rats (2007). Kearbey and colleagues treated 120 female rats for 120 days after ovariectomy. S-4 maintained whole-body and trabecular bone mineral density and cortical content, increased femoral bone strength on biomechanical testing and reduced body fat, in a model of accelerated bone loss.
Pharmacokinetics in rats (2004). Kearbey and colleagues gave S-4 intravenously and orally to male rats across a range of doses. Clearance was slow, the half-life was between 2.6 and 5.3 hours, and oral bioavailability was complete at the lower doses and dose-dependent above that.
UK market analysis of SARM products (2021). Leaney and colleagues, working in a UK laboratory, analysed supplement products marketed as SARMs to UK consumers. Findings ranged from products with no active ingredient to products containing undeclared prohibited substances, and where a SARM was present its concentration frequently did not match the label.
All of the andarine efficacy data above come from rats. There are no published controlled human trials, and none of these findings is a claim about the products listed on this page.
Brands of andarine we stock
- iMuscle Andarine S-4, 15mg, 60 capsules. Capsule form, 900mg of compound per pack. A certificate of analysis is shown on the listing only where iMuscle has supplied one for the batch we hold; if none is displayed, none is available for that batch. View the iMuscle Andarine listing.
Free Muscle does not currently produce its own andarine, so there is no Janoshik-assayed Free Muscle batch on this page at present. Any Free Muscle-brand line added later will carry batch-level Janoshik testing like the rest of our range.
How to compare them
Multiply strength per capsule by capsules per pack to get total milligrams (15mg by 60 gives 900mg). Divide the pack price by that figure for cost per milligram, which is how a 15mg pack is compared fairly against a 25mg or 50mg pack from another supplier. Then weigh the certificate. Market analyses of SARM products, including the 2021 UK study above, have repeatedly found labels that do not match contents, so a batch-specific COA from an independent laboratory is the only way to know what a pack contains. Our guide to price per milligram covers the arithmetic.
Batch testing and certificates of analysis
A certificate of analysis (COA) answers the two questions that matter about an andarine capsule: is the compound what the label says, and how much is present. A genuine batch certificate is issued by an independent laboratory, names the lot number, and reports identity (by HPLC or mass spectrometry against a reference standard) and assayed purity or content.
Every Free Muscle-brand batch is assayed by Janoshik Analytical, an independent laboratory, and the certificate for the batch you receive is sent on request by email. For other brands we show a COA only where the manufacturer has supplied one for the batch we hold. A generic PDF with no batch number, or one dated long before the product was made, is not a batch certificate and tells you nothing about the capsules in your hand. Our lab tests page explains how to read a Janoshik certificate and match it to your batch.
Legal status in the UK
Andarine is not a licensed medicine in the United Kingdom. It has never been granted a marketing authorisation by the MHRA, and it is not an authorised food supplement or a permitted novel food ingredient. It cannot legally be sold or labelled for human consumption. Free Muscle sells andarine to adults aged 18 or over for laboratory and research purposes only, and every listing states this. Andarine is named on the World Anti-Doping Agency Prohibited List under S1.2, Other Anabolic Agents, and is prohibited at all times. Anyone subject to anti-doping rules should treat any product in this class as prohibited at all times, in and out of competition. For a fuller overview of the class, see our research guide to SARMs.
Storage and handling
Keep andarine capsules in the original sealed container in a cool, dry place away from light and heat. Do not decant into unlabelled containers, and record the batch number so that a COA request can be matched to the exact material. Keep out of reach of children and pets, and follow standard laboratory good practice: gloves when handling, no eating or drinking in the work area, and disposal in line with local rules for research chemicals.
Delivery and returns
Orders are sent by FreeMuscle LTD, a UK company in Scunthorpe, with free tracked delivery to UK addresses and plain packaging. Same-working-day processing applies to orders placed before 2pm, Monday to Friday, and EU delivery takes 3 to 7 working days. Unopened items are returnable within 30 days. We sell only to customers aged 18 or over. Details are on the shipping page and the guarantee page.
Related reading
- What are SARMs? The 2026 research guide
- SARMs explained: how selective androgen receptor modulators work
- How to read a certificate of analysis
- Price per milligram: the only honest way to compare SARMs and peptides
Related collections: Ostarine (MK-2866), S-23, iMuscle, all SARMs.
Andarine is sold strictly for laboratory research use only. It is not a licensed medicine, has not been evaluated or approved by the MHRA, EMA or FDA, is not a food supplement and is not for human consumption. Buyers must be 18 or over. Nothing on this page is medical advice, dosing advice or a recommendation to use this compound in any way; the published findings summarised above describe study participants and laboratory models, not the products listed.
Frequently asked questions
Is andarine legal in the UK?
Andarine is not a controlled drug in the UK, but there is also no permission to sell it for people to take. It holds no MHRA marketing authorisation and is not an authorised food supplement, so any sale or labelling for human consumption would be unlawful. We supply andarine to adults for laboratory research only, and customers must be 18 or over.
Is andarine a SARM or a steroid?
Andarine is a non-steroidal selective androgen receptor modulator of the aryl-propionamide family, derived from the anti-androgen bicalutamide. It acts on the androgen receptor but has no steroid skeleton and is not converted to oestrogen or dihydrotestosterone. WADA classes it as an anabolic agent, and it has never been approved as a medicine.
What is the difference between andarine and ostarine?
Both are aryl-propionamide SARMs from the same academic programme. Ostarine (enobosarm) replaced the nitro group in andarine with a cyano group and became the compound GTx took through phase 3 trials. Andarine stalled at an early stage and has no published controlled human trials. Andarine is also associated anecdotally with visual disturbance, which is not reported for ostarine.
Has andarine been tested in humans?
No controlled human trial results for andarine have been published in the peer-reviewed literature. GTx investigated it in the mid-2000s but shifted development to ostarine. The published efficacy data come entirely from rat studies of muscle, bone, prostate and body composition. There are no human data on long-term effects or on the visual side effect reported anecdotally.
How do I verify the batch I received?
iMuscle supplies the andarine on this page, and any certificate of analysis for the batch we hold is shown on the listing itself. There is no email request route for third-party brands, because we can only share what the manufacturer has issued. When a certificate is displayed, confirm the lot number against your label and read the identity and content lines. Our guide to reading a COA explains what each figure means.
Is andarine detectable in sports drug testing?
Yes. Andarine is named on the WADA Prohibited List under S1.2, Other Anabolic Agents, and is banned at all times. Anti-doping laboratories detect it and its metabolites routinely, and it is one of the SARMs most often identified in analyses of products sold online. Anyone subject to anti-doping rules should treat it as prohibited.
Which strength of andarine should I choose?
That is not a question we answer. Andarine is sold for laboratory research only, so strength, quantity and use are matters for the research protocol rather than for us. What we do publish is the strength per capsule (15mg) and capsules per pack (60) so that total content and cost per milligram can be compared with other listings. Nothing here is dosing or medical advice.
How is andarine shipped, and can I return it?
Andarine ships like everything else at Free Muscle: free, tracked and in plain packaging for UK addresses, with EU delivery in around 3 to 7 working days. The cut-off for same-working-day processing is 2pm, Monday to Friday. Our 30-day return window covers unopened items only, so keep the seal intact if you may need to send a pack back. Customers must be aged 18 or over.