Boldenone (Equipoise)

What boldenone is

Boldenone is an anabolic androgenic steroid, chemically a testosterone with an additional double bond in the first ring of the steroid skeleton. It is sold as an ester, boldenone undecylenate, for injection; the best-known name is Equipoise, in the scene EQ for short.

It is approved only in veterinary medicine: in the US as a prescription drug for debilitated horses, when weight, coat or general condition are to improve. It is not approved for humans; anyone who uses it anyway is using a veterinary drug or an underground product. The page Anabolic steroids gives an overview of the whole group of substances.

How it works

Boldenone binds to the androgen receptor. This results in anabolic and masculinizing effects and, as with any supplied androgen, feedback on the hormonal axis: the body’s own testosterone production is shut down.

How strong these effects are in humans has not been measured. What is said about boldenone comes from veterinary medicine and from analogy with other anabolic steroids. In humans, only how the body breaks down and excretes the substance has been studied.

What the studies show

Schänzer and Donike 1992: metabolism in the human body

The research group gave boldenone to volunteers and examined their urine. It identified boldenone itself and nine metabolites; more than 95 % of the metabolites are excreted as stable conjugates. Effects on muscles, strength or blood values were not the subject of the study.

Piper 2010: endogenous or supplied?

Boldenone is not approved for humans but turns up in doping samples. The research group developed a method that determines the origin via the carbon isotope ratio. Of 23 samples examined, 11 did not fit an external intake; two of them came from the same athlete one month apart – a strong indication that some people form boldenone themselves in traces.

White 2018: heart failure in a strength athlete

A 39-year-old weightlifter was admitted to hospital with acute, severe heart failure; the pumping function of the left ventricle was about 15 %. The treating physicians attributed the heart muscle disease to testosterone and boldenone in the preceding three months. A single case does not prove a connection, but it fits the cardiac findings in anabolic steroid users overall.

Winnett 2011: false kidney finding

A 37-year-old was referred because of abnormal kidney values, without symptoms and without further signs of kidney disease. The cause of the markedly elevated creatinine was boldenone. The case shows that anabolic steroids can distort laboratory values – and that physicians need to know about the use in order to interpret findings correctly.

Where the data stop

• No efficacy study. On muscle mass, strength, blood formation or performance there is no human study and no entry in ClinicalTrials.gov.
• No safety study. Individual cases are known; how often harm occurs, nobody knows.
• Veterinary medicine is no substitute. The approval for horses says nothing about benefits and risks in humans.
• Products from the gray market. In Zurich drug checking for steroids, 52 % of the samples tested were counterfeit; the content and purity of underground products are unknown.

Status, approval and legal

Boldenone is not approved for humans. In the US, boldenone undecylenate is approved as a prescription veterinary drug for horses. In Germany, finished medicinal products may only be placed on the market with a marketing authorization (§ 21 of the German Medicinal Products Act).

Boldenone is listed by name in the annex of the German Anti-Doping Act. Manufacturing, trafficking and placing on the market for the purpose of doping in sport are prohibited, as are acquisition, possession and bringing into Germany in non-small quantities for this purpose; violations are punishable under § 4 with imprisonment of up to three years or a fine. In sport it is prohibited in and out of competition under the WADA Prohibited List 2026 under S1.1, anabolic androgenic steroids.

Safety

There are no substance-specific safety data on boldenone in humans, only case reports: severe heart failure under testosterone and boldenone and apparent kidney damage due to elevated creatinine. Everything else comes from the data on the class of substances: supplied androgens shut down the body’s own hormonal axis, with reduced fertility, and strain the heart and blood vessels; in addition there are psychological and metabolic effects, and in women masculinization. The Endocrine Society describes the widespread assumption that use is safe or manageable as a misjudgment.

Two practical points, without finger-wagging. First, boldenone distorts laboratory values such as creatinine; anyone having blood values measured should disclose the use. Second, a veterinary drug or underground product has not been tested for humans, and a good half of the steroid samples tested in Zurich were counterfeit. Before any step here, a conversation with a physician is needed, because of consequences that can be permanent.

Sources

• Code of Federal Regulations, 21 CFR 522.204 – boldenone: approval as a veterinary drug for horses
• Piper T et al., Drug Test Anal 2010 – carbon isotope ratio of boldenone in urine; not approved for humans, endogenous formation possible
• Schänzer W, Donike M, Biol Mass Spectrom 1992 – metabolism of boldenone in humans, urinary excretion
• White M et al., Can J Cardiol 2018 – acute severe heart failure after testosterone and boldenone, case report
• Winnett G et al., Nephrol Dial Transplant 2011 – apparent kidney disease due to elevated creatinine under boldenone, case report
• Magnolini R et al., Harm Reduction Journal 2025 – Zurich drug checking for steroids: 52 % of samples counterfeit
• Pope HG et al., Endocr Rev 2014 – health consequences of performance-enhancing substances, Endocrine Society scientific statement
• German Medicinal Products Act (AMG), § 21 marketing authorization requirement
• German Anti-Doping Act (AntiDopG), § 2, § 4 and annex
• NADA – Prohibited List 2026, informational German translation (S1.1 anabolic androgenic steroids)