Boldenone cypionate is boldenone with a cyclopentylpropionate (“cypionate”) ester attached. It is the same ester used in testosterone cypionate, placed on a different steroid. It is an anabolic-androgenic steroid (AAS) with no approved medical use, so any product sold under this name comes from outside the regulated drug supply.

Boldenone cypionate is not an approved medicine for people or animals in the US. The only approved boldenone product is the undecylenate ester, sold as Equipoise for horses (21 CFR 522.204). We found no clinical trial, pharmacokinetic study or case report that names the cypionate ester specifically. What can be said about it comes from its chemistry, from the boldenone literature in general, and from regulators.

This page summarizes what the chemistry databases, regulators and the limited boldenone research report. It is for education only and is not medical advice.

Property	Detail
Drug class	Injectable anabolic-androgenic steroid; 17β-cypionate ester of boldenone
Approval	None, human or veterinary, in the US
Formula / weight	C₂₇H₃₈O₃, 410.6 g/mol (PubChem CID 71314193)
Boldenone content	≈70% of the ester’s weight (100 mg ester ≈ 70 mg boldenone)
Half-life	Never measured in people or animals; the same ester on testosterone has a labeled half-life of about 8 days
Human trials	None
US schedule	Controlled substance, Schedule III (boldenone, including its esters)
WADA status	Prohibited at all times (S1.1 anabolic androgenic steroids)

What it is

Boldenone is testosterone with an extra double bond between carbons 1 and 2 of the A-ring. Its chemical name is 17β-hydroxyandrost-1,4-diene-3-one (21 CFR 1308.13). The Equipoise page covers the parent steroid, its relatives such as methandienone and dihydroboldenone, and its natural occurrence in more depth.

In the cypionate form, a 3-cyclopentylpropanoic acid is attached at the 17β-hydroxyl group. PubChem lists the compound as “Boldenone Cypionate,” CAS 106505-90-2, with the formula C₂₇H₃₈O₃ and a molecular weight of 410.6 g/mol (PubChem: boldenone cypionate). Boldenone alone weighs 286.4 g/mol (PubChem: boldenone), so about 70% of each labeled milligram is boldenone.

The ester changes how much boldenone each milligram delivers, as the PubChem molecular weights show:

Ester	Formula	Molecular weight	Boldenone share by weight
Boldenone acetate	C₂₁H₂₈O₃	328.4 g/mol	≈87%
Boldenone cypionate	C₂₇H₃₈O₃	410.6 g/mol	≈70%
Boldenone undecylenate (Equipoise)	C₃₀H₄₄O₃	452.7 g/mol	≈63%

Sources: PubChem: boldenone acetate; PubChem: boldenone undecylenate.

We found no record of a pharmaceutical boldenone cypionate product. A 2008 pharmacology review, listing the esters used in injectable steroid preparations, names undecylenate for boldenone and does not mention a cypionate. The same review notes that boldenone is restricted to veterinary use in some countries but is still used by athletes and bodybuilders (Kicman, Br J Pharmacol 2008).

How it behaves in the body

There are no pharmacokinetic data for boldenone cypionate in any species. What is known is general to steroid esters:

The ester is a release mechanism. Esterifying the 17β-hydroxyl group slows absorption from the oil vehicle. Once in the circulation, blood esterases quickly cleave the ester and release the active steroid (Kicman 2008).
Chain length sets the pace. In general, the longer the acid chain, the more slowly the drug is released and the longer it acts. The formulation and oil also matter (Kicman 2008).
The same ester on testosterone. The Depo-Testosterone label gives the half-life of intramuscular testosterone cypionate as approximately eight days (FDA label).

That testosterone figure cannot simply be transferred. Boldenone is a different steroid, and no study has measured how quickly boldenone cypionate leaves an injection depot. The only measured boldenone kinetics come from horses given an intramuscular injection of 1.1 mg/kg, where the median elimination half-life was 123 h (Soma et al., J Vet Pharmacol Ther 2007). That is the veterinary undecylenate setting, in a different species.

Once the ester is removed, the body handles the boldenone the same way whatever ester it came from. In a study where 3 men and 3 women each took a single 30 mg oral dose of boldenone, urine contained boldenone, its 17α-epimer and the metabolite 5β-androst-1-en-17β-ol-3-one (BM1). For most volunteers, BM1 concentrations were higher than boldenone’s, and the pattern did not differ by sex (Wu et al., J Pharm Biomed Anal 2015).

Regulatory status

No approved product. FDA’s animal drug regulation for boldenone covers only boldenone undecylenate at 25 or 50 mg/mL, for debilitated horses, at 0.5 mg per pound body weight IM, repeatable at 3-week intervals (21 CFR 522.204). There is no human approval for any boldenone ester.
US controlled substance. Schedule III lists boldenone among the anabolic steroids and covers “its salts, esters and ethers,” so the cypionate is controlled the same way as the undecylenate (21 CFR 1308.13).
Sport. The WADA 2026 Prohibited List names boldenone under S1.1 anabolic androgenic steroids. S1 substances are prohibited in and out of competition and are non-specified substances (WADA 2026 Prohibited List).

What the research shows

In humans

No randomized or controlled trial has tested boldenone cypionate, or boldenone in any form, for muscle, strength, body composition or any medical condition. Any claim that the cypionate acts faster than the undecylenate, or has its own distinct effect profile, is not backed by a published measurement.

The Endocrine Society scientific statement on performance-enhancing drugs reports that testosterone, boldenone and trenbolone are the drugs most often detected among illicit users in the US. It notes that boldenone’s status as a veterinary steroid has not reduced its popularity (Pope et al., Endocr Rev 2014). That statement does not say which esters were involved.

Drug testing

Because small amounts of boldenone can occur naturally in urine, doping labs use carbon isotope ratios to tell injected boldenone from the body’s own. In 39 boldenone preparations seized in Switzerland and Germany between 2013 and 2018, all had isotope ratios in the range expected for synthetic steroids, −26.7 to −30.3‰ (Piper and Thevis, Drug Test Anal 2022).

Another approach is to detect the intact ester in blood before esterases cleave it. This avoids the problem that the freed steroid, once in urine, can look like the body’s own. A Japanese anti-doping laboratory developed a dried blood spot method that detects six boldenone esters, among 28 steroid esters, with limits of detection from under 0.1 to 0.9 ng/mL (Miyamoto et al., Drug Test Anal 2025).

Side effects and risks

There are no safety data specific to boldenone cypionate. The few human reports involve boldenone without a stated ester, usually together with other drugs, and the main evidence is for AAS as a class.

Reports involving boldenone

Kidneys. A 37-year-old man was referred for a raised creatinine and low estimated kidney function with no other signs of kidney disease. The authors linked the raised creatinine to boldenone use and warned that creatinine alone can lead to a misdiagnosis of kidney disease (Winnett et al., Nephrol Dial Transplant 2011).
Heart. A 39-year-old weightlifter presented in fulminant heart failure, with left ventricular systolic function (the pumping strength of the main chamber) estimated at 15%. His dilated cardiomyopathy was attributed to testosterone and boldenone use over the previous 3 months (White et al., Can J Cardiol 2018).

Single case reports cannot prove that boldenone caused these problems.

Class effects of anabolic steroids

The Endocrine Society statement rates the following AAS effects as well recognized and of probable serious concern (Pope et al. 2014):

dyslipidemia (lower HDL, higher LDL) and atherosclerotic disease;
cardiomyopathy;
suppression of the hypothalamic-pituitary-testicular axis, with hypogonadism after stopping;
virilizing effects in women.

It also lists polycythemia (too many red blood cells), gynecomastia (breast tissue growth in men) and hypertension as well-recognized effects, and reports soft-tissue abscesses from steroid injections. Nothing shows that boldenone cypionate is an exception to any of these.

Product quality

Because no approved product exists, any boldenone cypionate comes from outside the regulated drug supply. Studies of seized steroids show the risk this carries:

Of 2,818 anabolic products seized by Brazil’s Federal Police between 2006 and 2011 and analyzed, 31.7% were counterfeit. Almost half of the fakes did not contain the declared substance (da Justa Neves et al., Forensic Sci Int 2013).
In 115 seized oil-based steroid products from Brazil, drugs including boldenone were found at widely varying concentrations, always at sub-doses (less than the labeled amount) (Coimbra et al., Forensic Sci Int 2021).

Key takeaways

An unapproved ester. Boldenone cypionate has no human or veterinary approval in the US. The only approved boldenone product is the undecylenate for horses.
About 70% boldenone by weight. The cypionate ester is lighter than the undecylenate, so each milligram carries slightly more boldenone.
Half-life unknown. No study has measured its kinetics. The approximately 8-day label half-life of testosterone cypionate is a different steroid and cannot be assumed to apply.
No human trials. Claims about its effects come from user reports. Safety signals for boldenone come from a few case reports and from AAS class effects.
Controlled and banned in sport. Boldenone and its esters are Schedule III in the US and prohibited at all times by WADA.

Sources

National Center for Biotechnology Information. Boldenone cypionate, PubChem CID 71314193. PubChem.
National Center for Biotechnology Information. Boldenone, PubChem CID 13308. PubChem.
National Center for Biotechnology Information. Boldenone acetate, PubChem CID 102247. PubChem.
National Center for Biotechnology Information. Boldenone undecylenate, PubChem CID 11954310. PubChem.
21 CFR 522.204. Boldenone. Electronic Code of Federal Regulations. eCFR.
21 CFR 1308.13. Schedule III. eCFR.
World Anti-Doping Agency. The 2026 Prohibited List. In effect January 1, 2026. WADA 2026 Prohibited List.
Pfizer. Depo-Testosterone (testosterone cypionate) injection, prescribing information. DailyMed.
Kicman AT. Pharmacology of anabolic steroids. Br J Pharmacol. 2008;154(3):502–521. PubMed.
Soma LR, Uboh CE, Guan F, McDonnell S, Pack J. Pharmacokinetics of boldenone and stanozolol and the results of quantification of anabolic and androgenic steroids in race horses and nonrace horses. J Vet Pharmacol Ther. 2007;30(2):101–108. PubMed.
Wu X, Gao F, Zhang W, Ni J. Metabolism study of boldenone in human urine by gas chromatography-tandem mass spectrometry. J Pharm Biomed Anal. 2015;115:570–575. PubMed.
Pope HG Jr, Wood RI, Rogol A, et al. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341–375. PubMed.
Piper T, Thevis M. Investigations in carbon isotope ratios of seized testosterone and boldenone preparations. Drug Test Anal. 2022;14(3):514–518. PubMed.
Miyamoto A, Ota M, Sato M, Okano M. Simultaneous detection of testosterone, nandrolone, and boldenone esters in dried blood spots for doping control in sports by liquid chromatography-tandem mass spectrometry. Drug Test Anal. 2025;17(1):42–55. PubMed.
Winnett G, Cranfield L, Almond M. Apparent renal disease due to elevated creatinine levels associated with the use of boldenone. Nephrol Dial Transplant. 2011;26(2):744–747. PubMed.
White M, Brennan E, Mi Ren KY, Shi M, Thakrar A. Anabolic androgenic steroid use as a cause of fulminant heart failure. Can J Cardiol. 2018;34(10):1369.e1–1369.e3. PubMed.
da Justa Neves DB, Marcheti RG, Caldas ED. Incidence of anabolic steroid counterfeiting in Brazil. Forensic Sci Int. 2013;228(1-3):e81–e83. PubMed.
Coimbra MA, Barbosa FS, Scheid C, et al. Mass spectrometry determination of seized oil-based anabolic-androgenic steroids products. Forensic Sci Int. 2021;328:111012. PubMed.

Boldenone Cypionate