Trenbolone acetate is a synthetic anabolic-androgenic steroid (AAS) made for cattle, not people. In the US it is approved only as a slow-release ear implant that makes beef cattle gain weight faster and convert feed more efficiently. The reference trenbolone-only implants, Finaplix-S and Finaplix-H, were made by Roussel UCLAF (Federal Register, 1997).
The single most important fact is that there is no FDA-approved human trenbolone medicine. FDA’s Drugs@FDA database lists no human trenbolone product (Drugs@FDA), and no randomized trials in people exist. What is known about its effects in humans comes from a small 1960s volunteer study, a single-subject metabolism study, surveys of people who use it, and case reports. Despite this, it is widely used in bodybuilding as an injectable oil.
This page summarizes what US regulations, toxicology reviews, animal studies and the limited human data report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Synthetic anabolic-androgenic steroid; 19-nor (estrane) steroid related to nandrolone |
| Approved use | Veterinary only: ear implants for beef cattle fed in confinement for slaughter |
| Human approval | None in the US; no human product listed in Drugs@FDA |
| Approved implant strengths | 140 mg or 200 mg alone; 40–200 mg combined with estradiol or estradiol benzoate (implant totals) |
| Formula and weight | C₂₀H₂₄O₃, 312.4 g/mol; trenbolone itself is 270.4 g/mol (≈87% of the ester’s weight) |
| Half-life | No human data for the acetate ester. In cows the ester is cleaved within minutes, and free trenbolone has a plasma half-life of ≈1.5 h |
| Key mechanism fact | Binds the human androgen receptor about as strongly as DHT; also binds the progesterone receptor |
| US status | Schedule III anabolic steroid; FDA-approved cattle implants are exempt only while used in animals |
| WADA status | Prohibited at all times (S1.1 anabolic androgenic steroids) |
What it is
Trenbolone’s chemical name is 17β-hydroxyestra-4,9,11-trien-3-one. Like nandrolone, it lacks the carbon-19 methyl group of testosterone, which makes it an “estrane” or 19-nor steroid. Unlike nandrolone, it has three double bonds in its ring system (at positions 4, 9 and 11). Trenbolone acetate adds an acetate ester at the 17β position (PubChem CID 66359; PubChem CID 25015).
| Form | Formula | Molecular weight | Notes |
|---|---|---|---|
| Trenbolone (free steroid, 17β-trenbolone) | C₁₈H₂₂O₂ | 270.4 g/mol | The active hormone |
| Trenbolone acetate | C₂₀H₂₄O₃ | 312.4 g/mol | The form in approved cattle implants; ≈87% trenbolone by weight |
Other esters exist, with different release rates. See Trenbolone Enanthate and Parabolan (Trenbolone Hexa).
Trenbolone has no 17α-methyl group (the feature that lets oral steroids such as oxandrolone survive the liver). This is visible in its chemical name.
How it acts on receptors
The acetate ester has no hormonal activity of its own. It is cleaved to 17β-trenbolone, the active compound. In laboratory binding studies (Bauer et al., APMIS 2000):
- Androgen receptor: 17β-trenbolone bound the recombinant human androgen receptor with an affinity similar to dihydrotestosterone (DHT). A later review describes its affinity as about three times that of testosterone (Yarrow et al., Steroids 2010).
- Progesterone receptor: it bound the bovine progestin receptor slightly more strongly than progesterone itself. This is a cow receptor tested in vitro, so the size of any effect in people is unknown.
- Metabolites: its two main metabolites, 17α-trenbolone and trendione, had less than 5% of its androgen receptor affinity.
- SHBG: binding to sex hormone-binding globulin was much lower than DHT’s.
Testosterone is converted in some tissues to the stronger androgen DHT by 5α-reductase. Trenbolone does not undergo this 5α-reduction to a more potent androgen. Researchers have proposed this as the reason it caused less prostate growth than testosterone in rats (Yarrow et al., Steroids 2010).
Pharmacokinetics
There are no formal pharmacokinetic studies of injected trenbolone acetate in humans. The numbers below come from cattle and rats, plus one human metabolism study, as summarized by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) (WHO Food Additives Series 23, 1988) and the primary papers.
| Setting | Finding |
|---|---|
| Cows, 10 mg IV radiolabeled trenbolone acetate | At 0.1 h, only 2% of radioactivity was still the acetate; 70% was free trenbolone |
| Cows, same study | Free trenbolone left the blood with a half-life of 1.5 h |
| Cows, 300 mg ear implant | Drug left the implant with a half-life of 68–84 days (60 days in lactating cows) |
| Human plasma, in vitro | Trenbolone bound mainly to albumin; about 4% was free |
| One human, oral radiolabeled 17β-trenbolone, 0.04 mg/kg | 54% of the dose appeared in urine by 26 h and 63% by 72 h |
| Rats, weekly IM trenbolone enanthate, 7 mg | Blood levels peaked within 48 h of each injection |
In the single human subject, the main urinary products were glucuronide conjugates of 17α-trenbolone, 17β-trenbolone and trendione. The authors noted that human metabolism differed significantly from that in rats (Spranger & Metzler, J Chromatogr 1991). The rat data come from a study of the enanthate ester (Yarrow et al., AJP-Endo 2011).
JECFA also cites a total blood clearance of 17β-trenbolone about twice that of testosterone.
The practical point is that the acetate ester is removed quickly, and free trenbolone itself is cleared quickly. How long trenbolone acetate persists after an injection of oil into human muscle has not been measured in a published study.
Regulatory status
Veterinary approval
FDA regulations approve trenbolone acetate only as implants placed under the skin of the ear in cattle (21 CFR 522.2476; 522.2477; 522.2478):
| Product type | Labeled amount | Labeled use |
|---|---|---|
| Trenbolone acetate alone (steers) | 140 mg, reimplanted once after 63 days | Improved feed efficiency |
| Trenbolone acetate alone (heifers) | 200 mg, last 63 days before slaughter | Faster weight gain, improved feed efficiency |
| With estradiol | 40–200 mg trenbolone acetate plus 8–40 mg estradiol | Faster weight gain, improved feed efficiency |
| With estradiol benzoate | 50–200 mg trenbolone acetate plus 7–28 mg estradiol benzoate | Faster weight gain, with or without improved feed efficiency |
The labels prohibit use in dairy cows and in animals intended for breeding. Revalor-S, a trenbolone acetate plus estradiol implant, was the reference product for later generics (Federal Register, 1997).
For residues in meat, FDA has set an acceptable daily intake for total trenbolone residue of 0.4 µg/kg body weight per day. It does not require a tolerance for cattle tissues (21 CFR 556.739).
Controlled substance status
Trenbolone is listed by name as a Schedule III anabolic steroid (21 CFR 1308.13). The DEA definition of “anabolic steroid” excludes steroids that are FDA-approved for implantation in cattle or other non-human species. However, anyone who prescribes, dispenses or distributes such a steroid for human use is treated as handling a controlled anabolic steroid (21 CFR 1300.01).
Sport
Trenbolone is named in section S1.1 (anabolic androgenic steroids) of the World Anti-Doping Agency 2026 Prohibited List, in force from January 1, 2026. Substances in S1 are prohibited at all times, in and out of competition, including their esters (WADA; Tractatenblad 2026, 25).
What the research shows
The only human administration study
In 1967, Krüskemper and colleagues gave male and female volunteers 5 or 10 mg of trenbolone acetate intramuscularly every other day for 14 days (Krüskemper et al., Arzneimittelforschung 1967). As summarized by JECFA (WHO Food Additives Series 23):
- the 5 mg dose produced nitrogen retention, an early marker of an anabolic (protein-building) effect;
- at 10 mg, some women had menstrual cycle disturbances;
- the 10 mg dose caused a slight but significant fall in urinary 17-ketosteroids (breakdown products of the body’s own androgens);
- blood protein, cholesterol and clotting tests were unaffected over the 2 weeks.
The summary does not report the number of participants. No study has measured muscle, strength or body composition in people given trenbolone.
Animal data on muscle, bone and prostate
Most efficacy data come from rats. In one study, 3-month-old male rats were castrated (orchiectomy) and given weekly trenbolone enanthate at three doses, a high dose of testosterone enanthate, or vehicle for 29 days (Yarrow et al., AJP-Endo 2011). These are results in rats:
| Group (weekly dose, per rat) | Levator ani/bulbocavernosus muscle vs intact controls | Prostate mass vs intact controls | Hemoglobin vs intact controls |
|---|---|---|---|
| Trenbolone 1.0 mg | +35–40% | No increase | No difference |
| Trenbolone 3.5 mg | +35–40% | No increase | ≈ +8–10% |
| Trenbolone 7.0 mg | +35–40% | +68% | ≈ +8–10% |
| Testosterone enanthate 7.0 mg | +35–40% | +84% | No difference |
All trenbolone doses partly prevented the bone density loss and visceral fat gain caused by castration. In a pilot arm of the same study, 7 mg/week trenbolone cut intact rats’ own testosterone by 80% and DHT by 70% within 10 days.
These findings led the authors to suggest trenbolone be studied as a muscle- and bone-sparing drug. That research has not moved into human trials. Rat doses and tissue responses cannot be translated directly to people.
Surveys of people who use trenbolone
The largest comparison used the Global Drug Survey 2024. It compared 237 men who had injected trenbolone in the past year with 909 men who used other AAS but not trenbolone (Bonenti et al., Drug Alcohol Rev 2026). Selected self-reported concerns:
| Concern | Other AAS, no trenbolone | Trenbolone |
|---|---|---|
| Negative impact on heart | 31.2% | 54.4% |
| Negative impact on liver | 22.4% | 42.2% |
| Hair loss | 27.6% | 42.6% |
| Gynecomastia (breast tissue growth) | 20.6% | 32.5% |
| Restlessness or irritability | 12.9% | 29.1% |
| Depression or low mood | 12.0% | 23.6% |
| Anger or aggression | 9.2% | 21.1% |
| Loss of interest in other things | 8.0% | 23.2% |
All differences above were statistically significant, with small to moderate effect sizes. The authors stress the limits: data were self-reported and cross-sectional, reflected perceived rather than diagnosed problems, and did not account for dose or other drugs used alongside trenbolone. The study cannot show that trenbolone caused these problems.
A smaller online survey of 282 men who use AAS found that 33% were currently using trenbolone and 55.3% had used it before (Piatkowski et al., Int J Drug Policy 2024). After adjusting for age and BMI, a higher trenbolone dose was associated with more verbal aggression (p = 0.045).
Side effects and risks
No controlled human trial has measured trenbolone’s side effects, so their true rates are unknown. The evidence comes from the surveys above, animal studies and case reports.
Suppression of natural hormone production
Like other androgens, trenbolone suppresses the body’s own testosterone. In rats, a weekly dose cut testosterone by 80% within 10 days (Yarrow et al., AJP-Endo 2011). In the 1967 human study, 10 mg every other day reduced urinary 17-ketosteroids. JECFA based its safety limit for meat residues on the drug’s anti-gonadotropic (sex-hormone-suppressing) activity in castrated monkeys (WHO Food Additives Series 23). In the Global Drug Survey, decreased fertility was reported by 26.2% of the trenbolone group vs 19.0% of the comparison group (Bonenti et al., 2026).
Mood and behavior
Both surveys link trenbolone use with more irritability, mood swings, low mood and aggression than other AAS use. A published case describes acute psychosis attributed to trenbolone (Bey et al., Therapie 2023). Neither the surveys nor a single case can establish how often this happens or prove cause.
Heart and other organs (case reports)
Single-patient reports cannot prove cause or show how common a problem is. Reports involving trenbolone include:
- a heart attack in a 23-year-old bodybuilder after long-term trenbolone acetate use (Shahsavari Nia et al., Emerg 2014);
- repeated acute pancreatitis in a 24-year-old man that recurred when he restarted trenbolone acetate (Kumar et al., Clin Toxicol 2019);
- severe hypercalcemia (calcium 15 mg/dL) with acute kidney injury (creatinine 6.02 mg/dL), after other causes were ruled out (Lizardo et al., Cureus 2026).
Women
In the 1967 study, 10 mg every other day disturbed some women’s menstrual cycles within 2 weeks (WHO Food Additives Series 23). No study has measured virilization (masculinizing changes such as voice deepening or facial hair) in women using trenbolone.
Product quality
Because no human pharmaceutical product exists, trenbolone used by people comes from unregulated sources. Dose, sterility and identity are not controlled by any regulator.
Key takeaways
- A cattle drug, not a human medicine. Trenbolone acetate is FDA-approved only as an ear implant for beef cattle, and FDA’s drug database lists no human trenbolone product.
- Very potent at the androgen receptor. It binds the human androgen receptor about as strongly as DHT, and it also binds the progesterone receptor in lab tests.
- Almost no human data. The only human dosing study is a 2-week trial from 1967 at 5–10 mg every other day. There are no human pharmacokinetic studies of the injected acetate.
- Rat studies are not human evidence. Muscle and bone effects with less prostate growth were seen in castrated rats; these findings have never been tested in people.
- Surveys point to more harms. Men who use trenbolone report more heart, liver, mood and aggression concerns than men using other AAS, though these surveys cannot prove cause.
- Controlled and banned in sport. It is a Schedule III anabolic steroid in the US and prohibited at all times by WADA.
Sources
- Food and Drug Administration. 21 CFR 522.2476 (trenbolone acetate), 522.2477 (trenbolone acetate and estradiol) and 522.2478 (trenbolone acetate and estradiol benzoate). Electronic Code of Federal Regulations. eCFR 522.2476; eCFR 522.2477; eCFR 522.2478.
- Food and Drug Administration. 21 CFR 556.739 Trenbolone. Electronic Code of Federal Regulations. eCFR.
- Food and Drug Administration. Implantation or injectable dosage form new animal drugs; trenbolone acetate (FR Doc 97-14104) and trenbolone acetate and estradiol (FR Doc 97-13820). Federal Register. May 29, 1997;62:29013 and May 27, 1997. govinfo (97-14104); govinfo (97-13820).
- Drug Enforcement Administration. 21 CFR 1300.01 (definition of anabolic steroid) and 21 CFR 1308.13(f) (Schedule III anabolic steroids). eCFR 1300.01; eCFR 1308.13.
- World Anti-Doping Agency. The 2026 Prohibited List, in force January 1, 2026. WADA; published text in Tractatenblad 2026, 25.
- Food and Drug Administration. Drugs@FDA: FDA-approved drugs. Drugs@FDA.
- National Center for Biotechnology Information. Trenbolone acetate, PubChem CID 66359; trenbolone, PubChem CID 25015. PubChem (acetate); PubChem (trenbolone).
- Joint FAO/WHO Expert Committee on Food Additives. Trenbolone acetate. In: Toxicological Evaluation of Certain Veterinary Drug Residues in Food. WHO Food Additives Series 23. Geneva: World Health Organization; 1988. INCHEM.
- Krüskemper HL, Morgner KD, Noell G. Clinical pharmacology of trienolones, a group of new anabolically actine aestrane-derivatives (4,9,11-oestratrien-17beta-ol-3-on) [in German]. Arzneimittelforschung. 1967;17(4):449–454. PubMed.
- Spranger B, Metzler M. Disposition of 17 beta-trenbolone in humans. J Chromatogr. 1991;564(2):485–492. PubMed.
- Bauer ER, Daxenberger A, Petri T, et al. Characterisation of the affinity of different anabolics and synthetic hormones to the human androgen receptor, human sex hormone binding globulin and to the bovine progestin receptor. APMIS. 2000;108(12):838–846. PubMed.
- Yarrow JF, McCoy SC, Borst SE. Tissue selectivity and potential clinical applications of trenbolone (17beta-hydroxyestra-4,9,11-trien-3-one): a potent anabolic steroid with reduced androgenic and estrogenic activity. Steroids. 2010;75(6):377–389. PubMed.
- Yarrow JF, Conover CF, McCoy SC, et al. 17β-Hydroxyestra-4,9,11-trien-3-one (trenbolone) exhibits tissue selective anabolic activity: effects on muscle, bone, adiposity, hemoglobin, and prostate. Am J Physiol Endocrinol Metab. 2011;300(4):E650–E660. PubMed.
- Bonenti B, Ahmadinejad B, Puljević C, et al. The Trenbolo(g)ne Sandwich: an international study comparing health harms among men who use anabolic-androgenic steroids with and without trenbolone. Drug Alcohol Rev. 2026;45(4):e70162. PubMed.
- Piatkowski T, De Andrade D, Neumann D, et al. Examining the association between trenbolone, psychological distress, and aggression among males who use anabolic-androgenic steroids. Int J Drug Policy. 2024;134:104636. PubMed.
- Bey C, Abdelghaffar W, Ach T, et al. A case of acute psychosis triggered by anabolic steroid abuse (trenbolone). Therapie. 2023;78(6):775–778. PubMed.
- Shahsavari Nia K, Rahmani F, Ebrahimi Bakhtavar H, et al. A young man with myocardial infarction due to trenbolone acetate; a case report. Emerg (Tehran). 2014;2(1):43–45. PubMed.
- Kumar V, Issa D, Smallfield G, Bouhaidar D. Acute pancreatitis secondary to the use of the anabolic steroid trenbolone acetate. Clin Toxicol (Phila). 2019;57(1):60–62. PubMed.
- Lizardo KC, Merchant S, Drone E. Hypercalcemia from trenbolone use: a case report. Cureus. 2026;18(1):e102580. PubMed.