Ligandrol (LGD-4033)

Ligandrol (LGD-4033) is a SARM (selective androgen receptor modulator — a drug that turns on the same cell switch as testosterone, but only in some tissues). Importantly, it is a small lab-made molecule, not a peptide. It is sold widely online and is popular in fitness circles, where it is pitched as a “safer” stand-in for anabolic steroids. The reality is more sobering: the actual human evidence comes down to one short early-stage study, the known harms (lowered natural hormones, worse cholesterol numbers, and several published cases of liver injury) are real, and it is an unapproved drug that is illegal to sell as a supplement and banned across sport.

What it is

LGD-4033 is a SARM — a small molecule, not a peptide. It latches onto the androgen receptor (the cell “docking port” that testosterone normally uses) and switches it partly on. The idea behind its design is to fire up that signal mainly in muscle and bone, while doing less to the prostate and other tissues than testosterone would. That selective behavior is the whole pitch for SARMs as a class. In practice, though, the selectivity is far from perfect (you can see this in the hormone-suppression data further down). It works as a pill you swallow. It was first developed by Ligand Pharmaceuticals and later handed off to Viking Therapeutics, who called it VK5211. It is not FDA-approved for anything and never finished development as a drug.

The claims

LGD-4033 is sold illegally and used in fitness and biohacking circles to build lean muscle, gain strength, “recomp” the body (lose fat while gaining muscle), and bounce back faster from training. It is often marketed as a “safer alternative to anabolic steroids” with fewer side effects. You’ll find it online and in some “bodybuilding supplement” products, where it is labeled as a research chemical or — misleadingly — as a dietary supplement. The honest medical interest, going back years, was in treating muscle wasting (cachexia, the severe muscle loss that comes with serious illness), age-related muscle loss (sarcopenia), and recovery after a hip fracture. None of that ever produced an approved product.

What the evidence actually shows

The one piece of solid human data is a single trial. Basaria et al. (2013) was a randomized, double-blind, placebo-controlled, ascending-dose Phase 1 study (an early safety test where the dose is stepped up gradually, and neither patients nor researchers know who got the real drug). It ran in 76 healthy young men over 21 days. Short term, LGD-4033 was generally well tolerated and, even in just three weeks, it raised lean body mass (muscle and other non-fat tissue) in a dose-dependent way — meaning the more they took, the bigger the effect. Fat mass did not change in a meaningful way, and PSA (a prostate blood marker) did not move significantly over that short window. But it did push down total testosterone and SHBG (a protein that carries sex hormones in the blood), again in a dose-dependent way, and it lowered HDL (“good”) cholesterol and triglycerides (a blood fat). Once men stopped taking it, hormone and lipid (blood fat) levels drifted back toward where they started. The key thing to remember: this was a short, small study looking at safety and how the drug behaves in the body over one brief stretch — not proof that it works or stays safe over the long haul.

For cachexia, Viking Therapeutics ran a Phase 2 trial of VK5211 (LGD-4033) in people recovering from a hip fracture (108 patients, 12 weeks). The company reported statistically significant, dose-dependent gains in lean body mass. That result came from the company itself (a top-line press release in 2017 and a conference presentation at ASBMR in 2018), the program never moved on toward approval, and there is no confirmed peer-reviewed (independently checked by outside experts) publication of it — so take it with the appropriate grain of salt. There is some lab-bench and mechanism research on how it binds the receptor and how selective it is, but it is limited. Bottom line, the evidence is thin: there are no large, long-term, peer-reviewed studies in people showing it works or that it is safe.

Legal and regulatory status

In the US, SARMs including LGD-4033 are not approved for any use and are not legal dietary-supplement ingredients. On October 31, 2017, the FDA put out a public warning that bodybuilding products containing SARMs put people at risk of heart attack, stroke, and life-threatening liver injury, and it has sent warning letters to companies selling them. Any product sold as a supplement that actually contains SARMs counts as an unapproved, misbranded drug.

As of June 2026, SARMs (including LGD-4033) are not federally controlled substances under the Controlled Substances Act (the law that schedules drugs like narcotics). Bills to schedule SARMs have been introduced in past sessions of Congress, but we can’t confirm any of them passed — so the safest way to think about SARMs is as legally restricted, unapproved drugs rather than as scheduled substances. SARMs are a separate category from anabolic-androgenic steroids and are not covered by the Anabolic Steroids Control Act (oxandrolone, by contrast, is a Schedule III anabolic steroid).

In sport, all SARMs — including LGD-4033 (ligandrol), ostarine/enobosarm (MK-2866), andarine (S-4), RAD140, S-23, and YK-11 — are banned at all times (both in and out of competition) under Section S1.2 (“Other Anabolic Agents”) of the WADA Prohibited List. LGD-4033 has been behind multiple athlete sanctions, sometimes traced back to contaminated supplements.

Safety

• Testosterone / HPG-axis suppression: The HPG axis is the hormone loop between the brain and the testes that controls testosterone. The Basaria trial showed LGD-4033 turned it down (dose-dependent, and reversible in the short term). This is real and exactly what you’d expect from something that switches on the androgen receptor.
• Lipid changes: The same trial documented drops in HDL (“good”) cholesterol and triglycerides — a signal that matters for heart health.
• Hepatotoxicity (liver damage caused by a drug): Several published case reports describe liver injury and jaundice (yellowing of the skin and eyes) tied to LGD-4033 use. For example, Flores et al. (2020) reported severe drug-induced liver injury / cholestatic hepatitis (a type where bile flow is blocked) with scarring (fibrosis) seen on a liver biopsy in a 32-year-old man, and a 2024 Cureus report described liver injury in a 52-year-old man after roughly three months of use. The FDA notes that SARM users in general have had liver injuries serious enough to require hospitalization. These are case reports and safety-monitoring signals rather than carefully counted rates, but they show real, documented harm.

A note on some related but different compounds (these are not LGD-4033 effects): andarine (S-4) is anecdotally linked to temporary vision changes; GW-501516 (Cardarine) is not a SARM at all but a PPARδ agonist (a drug that activates a fat- and energy-metabolism switch), which GlaxoSmithKline dropped around 2006–2007 after long-term rat studies showed tumors in several organs; and SR9009 (Stenabolic) is a REV-ERB agonist research chemical (it acts on a body-clock protein), also not a SARM. GW-501516 and SR9009 are banned in sport under WADA Section S4 (Hormone and Metabolic Modulators), with GW-501516 listed specifically as a PPARδ agonist.

Bottom line

The strongest real human evidence for LGD-4033 is a single, short 3-week Phase 1 trial showing a modest gain in lean mass alongside drops in testosterone, SHBG, HDL, and triglycerides. Whether it works or stays safe over the long term in people is unproven. The documented harms — lowered testosterone, worse cholesterol numbers, and multiple published cases of liver injury — are real. It is an unapproved drug, illegal to sell as a supplement, and banned in sport.

Evidence grade: 7/10 · Moderate.

Sources

• Basaria S, et al. The safety, pharmacokinetics, and effects of LGD-4033 in healthy young men. J Gerontol A Biol Sci Med Sci. 2013 (PMID 22459616)
• Flores JE, et al. Ligandrol (LGD-4033)-Induced Liver Injury. ACG Case Reports J. 2020 (PMC7304490)
• LGD-4033 and a Case of Drug-Induced Liver Injury. Cureus 2024 (PMID 39421081)
• FDA consumer warning, Oct 31, 2017 — Certain bodybuilding products put consumers at risk
• USADA — SARMs: Prohibited Class, Anabolic Agents
• WADA — The Prohibited List
• Viking Therapeutics — VK5211 Phase 2 top-line results (company press release, 2017)
• GW501516 — development history, PPARδ mechanism, 2006–2007 discontinuation over rodent carcinogenicity (Wikipedia)