Boldenone Undecylenate
17 beta-hydroxyandrosta-1,4-dien-3-one
Also known as: Equipoise · Vebonol · Ba-29038 · boldenone undecenoate
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| As an appetite stimulant | 5 mg (total dose) IM/SC every 7 days | IM/SC | q7d | — | 🌎 NA |
- As an appetite stimulant: Anabolic steroids not as effective as many other appetite stimulants and may be associated with hepatotoxicity
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Debilitated horses (improvement in weight, haircoat, or general physical condition) | 1.1 mg/kg IM; may repeat in 3 week intervals | IM | q3w | — | 🌎 NA |
| Debilitated horses | 1 mg/kg IM; repeated at 3 week intervals | IM | q3w | — | 🌎 NA |
- Debilitated horses (improvement in weight, haircoat, or general physical condition): Most horses will respond with one or two treatments. ARCI UCGFS Class 4 Drug.
- Debilitated horses: ARCI UCGFS Class 4 Drug.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Boldenone undecylenate is a long-acting, injectable anabolic steroid derived from testosterone. It is primarily labeled for use in veterinary medicine to treat debilitated horses, aiding in the improvement of weight, hair coat, and general physical condition.
In small animal medicine, it has historically been used off-label as an appetite stimulant in cats, though its use has largely been supplanted by safer and more effective alternatives due to the risk of hepatotoxicity.
Clinical Pearl: Boldenone is formulated as an undecylenate ester in a sesame oil vehicle, which delays its absorption from the intramuscular injection site and provides a sustained release over several weeks. Due to its muscle-building properties, it is a Schedule III (C-III) controlled substance in the US and carries a high risk for human abuse and diversion.
Mechanism of action
Boldenone works by binding to intracellular androgen receptors in muscle and other tissues → the receptor-steroid complex translocates to the nucleus → alters gene transcription → promotes protein synthesis, nitrogen retention, and tissue building (anabolism) while reversing catabolism.
- Erythropoiesis: Stimulates red blood cell production, likely by increasing the production of erythropoietic stimulating factor (erythropoietin).
- Endocrine Feedback: High doses cause negative feedback on the hypothalamus and pituitary gland → inhibits Luteinizing Hormone (LH) and Follicle Stimulating Hormone (FSH) → suppresses endogenous testosterone release and impedes spermatogenesis.
- Electrolyte Balance: Causes retention of nitrogen, sodium, potassium, and phosphorus, and decreases urinary excretion of calcium.
Safety & warnings
Contraindications
- Stallions intended for reproduction
- Pregnant mares (Category X - risk of fetal masculinization)
- Non-pregnant mares intended for reproduction
- Horses intended for food purposes
- Patients with hepatic dysfunction
- Patients with hypercalcemia
- Patients with a history of myocardial infarction
- Patients with pituitary insufficiency
- Patients with prostate carcinoma or benign prostatic hypertrophy
Adverse effects
- Androgenic effects (over-aggressiveness)
- Detrimental effects on testis size and sperm production in males
- Altered sexual behavior, shortened estrus, and reduced pregnancy rates in females
- Clitoral enlargement in females
- Hepatotoxicity
- Sodium and water retention
Precautions
Pregnancy Category X: The risk of use outweighs any possible benefit due to fetal masculinization.
Hepatotoxicity: Anabolic steroids have the potential to cause hepatic toxicity; use with extreme caution and monitor liver enzymes.
Human Abuse Potential: Boldenone is a target for human abuse (bodybuilding/athletics). Veterinarians must be vigilant against diversion scams and ensure strict inventory control.
Drug interactions
Anabolic agents may potentiate the effects of anticoagulants; monitoring of INR and dosage adjustment are recommended.
May enhance the edema that can be associated with ACTH or adrenal steroid therapy.
May decrease blood glucose and decrease insulin requirements; diabetic patients may need dosage adjustments.
Monitoring
- Androgenic side effects (e.g., aggression, behavioral changes)
- Fluid and electrolyte status, if indicated
- Liver function tests, if indicated
- Red blood cell count and indices, if indicated
- Weight and appetite
Pharmacokinetics
Absorption
Considered a long-acting anabolic, with effects persisting up to 8 weeks due to the undecylenate ester and oil vehicle.
Distribution
Unknown if the anabolic agents cross into milk.
Overdose
Sodium and water retention can occur after overdosage of anabolic steroids. It is suggested to treat supportively and monitor liver function should an inadvertent overdose be administered.
Available products
Formulations
- Injection (oil vehicle)
Veterinary
- Boldenone Undecylenate for Injection: 25 mg/mL in 10 mL vials
- Boldenone Undecylenate for Injection: 50 mg/mL in 10 mL & 50 mL vials; Equipoise (Pfizer); (Rx, C-III)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Boldenone injection should be stored at room temperature; avoid freezing. Because boldenone injection is in an oil vehicle, it should not be physically mixed with any other medications.
Client information
Important Security Notice: Because of the potential for abuse by humans, anabolic steroids are controlled drugs. Boldenone must be kept in a secure area and strictly out of the reach of children and unauthorized individuals.
- Monitor for Liver Issues: Contact your veterinarian immediately if your pet develops yellowing of the whites of the eyes or gums (jaundice), a decreased appetite, or severe lethargy.
- Behavioral Changes: Watch for signs of increased aggression or other unexpected behavioral shifts.
- Administration: This medication is given by injection. Follow your veterinarian's exact schedule for follow-up doses.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.