SARMs Store sells research compounds only. Nothing on this page is medical advice or an instruction for human use.
Muscle gain is what this entire category was built on, and it is the claim most often inflated. The useful thing about selective androgen receptor modulators, compared with most compounds sold as research chemicals, is that several of them have been through human trials with dual-energy X-ray absorptiometry measurement of lean body mass. Real numbers exist. They are much smaller than the figures quoted in forum posts, and they were produced in populations very different from the people reading about them. This guide sets out each trial result in the units the researchers reported, then puts them next to two reference points: ordinary resistance training and testosterone.
What these compounds are
A SARM binds the androgen receptor, the same receptor testosterone acts on, but was engineered to act as a tissue-selective agonist, with more activity in muscle and bone and less in prostate, skin and hair follicle. None is converted to oestrogen or to dihydrotestosterone, which is the basis of the selectivity claim. MK-677, which appears in almost every bulking discussion, is not a SARM at all. It is an orally active growth hormone secretagogue that raises growth hormone and IGF-1 through the ghrelin receptor.
What the trials found
Ostarine, phase II. Dalton and colleagues, Journal of Cachexia, Sarcopenia and Muscle, 2011. 120 healthy older men and postmenopausal women, placebo or 0.1, 0.3, 1 or 3 mg of enobosarm daily for 12 weeks. At 3 mg, lean body mass rose by about 1.3 kg relative to placebo, the effect was dose-dependent, and stair-climb power improved by roughly 15 per cent. The participants were not on a training programme.
LGD-4033, phase I. Basaria and colleagues, Journals of Gerontology, 2013. 76 healthy young men, placebo or 0.1, 0.3 or 1 mg daily for 21 days. Lean body mass increased by about 1.21 kg at 1 mg over just three weeks, with no resistance training component. This remains the most efficient result per unit of time in the literature and the reason LGD-4033 is regarded as the most potent per milligram of the well-studied compounds. Testosterone, SHBG, LH, FSH and HDL all fell in a dose-dependent way.
VK5211, hip fracture. LGD-4033 was licensed and taken into a phase II trial under the code VK5211 in patients recovering from hip fracture. The sponsor reported dose-dependent increases in lean body mass over 12 weeks in 2018. That result was released by the company rather than published in a peer-reviewed journal, which is why it should be weighted lower than the studies above, and it is quoted here with that caveat attached.
MK-677, two years. Nass and colleagues, Annals of Internal Medicine, 2008. 65 healthy adults aged 60 to 81 on 25 mg daily. Fat-free mass increased by about 1.1 kg relative to placebo over one year, IGF-1 rose to young-adult levels, and fat mass did not change significantly. Strength and function did not improve in step with the body composition change.
RAD-140. The only human study is the first-in-human oncology trial in women with hormone receptor positive breast cancer reported by LoRusso and colleagues in Clinical Breast Cancer in 2022. It measured tumour response and safety, not lean mass, and raised liver transaminases were the most common adverse event. Everything said about RAD-140 and muscle comes from animal work.
YK-11. There is no human data at all. The compound’s reputation comes from cell-culture work by Kanno and colleagues published in the Biological and Pharmaceutical Bulletin in 2011, showing effects on follistatin expression in cultured mouse myoblasts. Cell culture is not a body.
How that compares with training and with testosterone
This is the comparison that is almost never made, and it is the one that matters.
Bhasin and colleagues, in the New England Journal of Medicine in 1996, randomised men to placebo or 600 mg of testosterone enanthate weekly, with and without resistance training, for ten weeks. Placebo with training produced about 1.9 kg of fat-free mass. Testosterone without training produced about 3.2 kg. Testosterone with training produced about 6.1 kg.
Against that, 1.3 kg from 12 weeks of enobosarm in untrained older adults and 1.21 kg from 21 days of LGD-4033 in untrained young men sit in roughly the same range as training alone. The LGD-4033 figure over three weeks is genuinely striking on a per-day basis, and it is also the shortest study, which is exactly the caution: short trials in untrained people produce the largest looking numbers. Nobody has run a trial of any SARM in trained lifters on a structured programme, which is the population that buys them.
Side effects reported
Dose-dependent suppression of total and free testosterone, SHBG, LH and FSH, reversing after discontinuation in the trials. Dose-dependent falls in HDL cholesterol. Raised liver transaminases specifically with RAD-140 in its human trial. Outside the trials, published case reports describe drug-induced liver injury associated with products labelled as SARMs, including the series by Flores and colleagues in Hepatology Communications in 2020 and cases involving RAD-140 and LGD-4033 products reported by Barbara and colleagues in ACG Case Reports Journal in 2020.
Four of the compounds covered here, MK-677, LGD-4033, RAD-140 and YK-11, are also supplied together in one capsule as the Mass Series all in one capsule, and the two-compound Beginner Muscle Stack pairs LGD-4033 with RAD-140 in separate bottles. No trial has tested any of these combinations, as our stacks guide explains.
Legal status in the UK, 2026
These compounds are not controlled under the Misuse of Drugs Act 1971 and are not Class C anabolic steroids. They are unlicensed medicines under the Human Medicines Regulations 2012 if sold or advertised for human use, which is what the MHRA enforces, so they are sold in the UK strictly as research material. All are prohibited in sport at all times under section S1.2 of the WADA list, with MK-677 under S2, and Ostarine remains the most frequently detected SARM in anti-doping samples.
How to check a supplier
Request the certificate of analysis for the specific batch you are buying. It should show identity confirmed by HPLC or LC-MS, a purity percentage, and a batch number matching the bottle. Look for UK manufacture, a clear per-capsule amount and capsule count, a research-only notice and verified-purchase reviews. Dexterz Labs Ligandrol LGD-4033 is made in the UK at 10 mg per capsule, 90 capsules per bottle, and batch certificates of analysis are being published on the product page as testing is completed.
Frequently asked questions
Which SARM has the best lean-mass evidence? Ostarine has the largest and longest human dataset. LGD-4033 produced the largest gain per day of any published trial, over only 21 days.
How much lean mass did the trials show? Around 1.2 to 1.3 kg in the two main studies, measured by DXA, in untrained participants.
Do SARMs work as well as steroids? No trial has compared them. The testosterone data from Bhasin and colleagues shows considerably larger gains than any SARM trial has recorded.
Is there human data for RAD-140 and YK-11 on muscle? No. RAD-140 has one oncology trial with different endpoints, and YK-11 has no human data at all.
Why are retail capsules stronger than trial doses? Because they are sold as research material rather than as medicines. There is no trial safety data at those amounts.
Do gains persist after stopping? No trial has followed body composition long after discontinuation, so there is no evidence either way.
Related reading
- LGD-4033 (Ligandrol): the research guide
- RAD-140 (Testolone): what the studies show
- MK-677 (Ibutamoren): what the research says
- SARMs stacks: what the research says about combining compounds
- Browse the range: SARMs for lean mass research
Research product: Dexterz Labs Ligandrol LGD-4033 10 mg, 90 capsules
Sources
- Dalton JT et al., J Cachexia Sarcopenia Muscle 2011;2:153-161. PubMed 22031847
- Basaria S et al., J Gerontol A Biol Sci Med Sci 2013;68:87-95. PubMed 22459616
- Nass R et al., Ann Intern Med 2008;149:601-611. PubMed 18981485
- Bhasin S et al., N Engl J Med 1996;335:1-7. PubMed 8637535
- LoRusso P et al., Clin Breast Cancer 2022;22:67-77. PubMed 34565686
- Kanno Y et al., Biol Pharm Bull 2011;34:318-323. PubMed 21372378
- Flores JE et al., Hepatol Commun 2020;4:450-452. PubMed 32140660
- Barbara M et al., ACG Case Rep J 2020;7:e00409. PubMed 33062783
- WADA Prohibited List 2026.