Boldenone undecylenate is an esterified form of boldenone, a synthetic anabolic-androgenic steroid structurally related to testosterone. The undecylenate ester contributes to prolonged release following administration.

Boldenone products have historically been associated primarily with veterinary medicine rather than routine human therapeutic use. Potential concerns include suppression of endogenous hormone production, elevated hematocrit, lipid changes, cardiovascular effects, and impaired fertility.