MedicationsHigh risk

Cardarine (GW-501516)

Also known as: Cardarine, GW-501516, GW501516, GW 501516, Endurobol, Cardarin

Not a SARM despite being sold as one — and the substance on this site whose development was stopped because it caused cancer in multiple organs across multiple species.

Substance family

Stimulants & thermogenics

They increase metabolic rate or mobilise fat through adrenergic and thermogenic mechanisms. Cardiac load is the shared limiting factor, and it adds up when they are combined.

Effects on

Fat loss Recovery & connective tissue

Which outcomes this substance acts on — descriptive, not a recommendation.

Strain profile

Where this substance is most likely to hit — a rough orientation, individually dependent on dose, duration and predisposition.

Liver

medium

Kidneys

low

Blood lipids

minimal

Hematocrit

minimal

Blood pressure

minimal

Hormonal axis

minimal

This substance causes

Liver strain

Dosing & protocols by goal

Rough orientation ranges as reported in harm-reduction literature — not an individual treatment plan. Doses are individual and open-ended; frequency depends on the ester or half-life.

Approved medical use

Medical

Dose

—

Frequency

—

Cycle length

—

None. GSK discontinued development in 2007 after long-term animal studies found tumours.

Endurance and fat loss (grey market practice)

Experimental

Dose

10–20 mg / day

Frequency

1× daily

Cycle length

8 weeks

The commonly reported range. No human dose was ever established, because the trials that would have established one were stopped.

Higher doses

Experimental

Dose

> 20 mg / day

Frequency

Varies

Cycle length

—

The animal carcinogenicity findings were dose- and duration-dependent. There is no basis for assuming a safe threshold in humans.

Supraphysiological doses carry significant health risks and are not legal without a medical indication. This information serves education and harm reduction, not as a usage recommendation. Accompanying blood work and — where relevant — a post-cycle plan (PCT) are essential. See the disclaimer.

Side effect & countermeasure

Typical problems and what you can do to reduce harm — at a glance. Does not replace medical monitoring.

Problem

Carcinogenicity in animal studies — the reason development stopped

Countermeasure

This is not a footnote and cannot be dosed around. In two-year rodent studies, cardarine produced tumours in multiple organs — liver, bladder, stomach, skin, thyroid, and others — across both rats and mice. GSK ended the programme in 2007. Whether this translates to humans is unknown, because the studies that would answer it were never done. Anyone using it is accepting a risk that has no upper bound in the available data.

Problem

Marketed and discussed as a SARM

Countermeasure

Cardarine does not touch the androgen receptor. It is a PPARδ agonist and causes no hormonal suppression — which is true, and is often presented as though it made the substance safe. The risk here is not hormonal.

Problem

Elevated liver values

Countermeasure

Reported in users. Check ALT, AST and GGT before and during; do not combine with other hepatotoxic substances.

Problem

Unverified grey-market quality

Countermeasure

Sold only as a research chemical. Content and purity are unverified. Only sources with an independent HPLC/MS analysis — though that does nothing about the underlying concern.

Problem

Long detection window in doping tests

Countermeasure

Detectable for an extended period and specifically screened for. WADA published a rare direct health warning about it, separate from the prohibition itself.

Overview

Cardarine is sold and discussed as a SARM, and it is not one. It does not bind the androgen receptor, causes no suppression and has no hormonal effects at all. That part of the marketing is accurate.

The reason it belongs on this site with a clear warning is different, and it is the most serious safety finding attached to any substance in this database apart from DNP.

Mechanism of Action

PPARδ is a receptor in the cell nucleus that regulates how tissue uses energy. Activating it shifts muscle metabolism towards fat oxidation and increases the expression of genes associated with endurance — in mice, the effect on running capacity was pronounced enough that the compound was nicknamed "exercise in a pill".

The effect is real, non-hormonal, and there is no suppression to recover from. On mechanism alone, cardarine looks like an unusually clean substance.

Then GlaxoSmithKline ran the standard two-year carcinogenicity studies required before human trials can proceed.

Tumours appeared across multiple organ systems — liver, bladder, stomach, skin, thyroid, and others — in both rats and mice, at a range of doses. The development programme was terminated in 2007 and never resumed by anyone.

That is the entire basis on which this substance should be judged. Whether the finding transfers to humans is genuinely unknown, because the trials that would answer it were stopped before they began. What can be said is that the mechanism PPARδ activation involves — cell proliferation and gene expression — is one where an animal carcinogenicity signal is not easy to dismiss.

Typical Context

Ten to twenty milligrams daily over eight weeks, used for endurance and fat loss, frequently stacked with SARMs on the reasoning that it adds no hormonal burden.

That reasoning is correct as far as it goes and misses the point entirely. The absence of suppression is often presented as evidence that cardarine is the safe part of a stack. It is the part with an unresolved cancer signal.

WADA's handling is telling. Prohibited substances are simply listed; cardarine received a separate, explicit public health warning — an unusual step that reflects how the anti-doping community read the toxicology.

Side Effects & Risks

Carcinogenicity in long-term animal studies across multiple organs and species
Elevated liver values
No hormonal suppression — which does not make it low-risk
Unverified grey-market quality
Long detection window in doping tests
No human safety data of any kind

Blood Work & Monitoring

There is no marker that detects the risk this substance carries. Liver values are worth tracking for a separate reason:

Liver values (ALT, AST, GGT) — before and during
Complete blood count — as a baseline

Harm-Reduction Notes

The carcinogenicity finding is the decisive fact — it stopped a pharmaceutical development programme
The absence of hormonal suppression is real and irrelevant to the actual risk
No dose has been established as safe, and none can be from the available data
Not a SARM; the comparison misleads about where the risk sits
Only sources with an independent analysis, though that addresses purity and not the substance itself
Unsuitable for anyone subject to doping controls

Legal status by region

Regulation differs considerably between jurisdictions and changes over time. This is a rough orientation, not legal advice — check the rules that apply where you are.

Region	Regulatory status
United States	Not approved for human useSold as a research chemical; the FDA has warned about SARM-marketed products generally.
EU / UK	No marketing authorisation
Most other jurisdictions	Unregulated grey area
Competitive sport	Prohibited at all timesWADA issued an unusual explicit health warning about this substance alongside the ban.

All content on this page is for information and harm-reduction purposes only. It is not medical advice, not a recommendation to purchase or use, and does not replace consulting a doctor. Legal status and enforcement vary by country and change; verifying the current rules in your own jurisdiction is your responsibility. For adults 18+ only. See the full disclaimer.