Nandrolone, an anabolic steroid, is used for the treatment of several diseases and is available in various pharmaceutical formulations. The most widely used pharmaceutical formulation is Deca-Durabolin, but other products, such as Keratyl eye drops solution, are also currently administered. Nandrolone is one of the most abused anabolic steroid in sports. Analyses for this anabolic steroid according to the World Anti-Doping Agency (WADA) protocol are based on the identification of the nandrolone two main urinary metabolites which, in humans, are glucuronides of 19-norandrosterone and 19-noretiocholanolone. A positive cut off limit of 2 ng/mL has been set by the anti-doping code for the first metabolite, 19-norandrosterone. In this preliminary study, an eye drops solution (Keratyl) containing a therapeutic dose of a nandrolone sodium sulphate was administered to several male volunteers during 3 days and urines were collected during 3 weeks. Surprisingly, contrary to all expectations, the urinary concentrations measured in urines reached 450 ng/mL and 70 ng/mL for norandrosterone and noretiocholanolone, respectively. Moreover, concentration levels near to 2 ng/mL were found, more than 2 weeks after the last administration, depending on individual metabolism. Inter-variability as well as intra-variability of nandrolone excretion kinetic, regarding this particular administration mode, were also evaluated. Quantification of nandrolone metabolites was performed by GC-MS. The method was previously validated in terms of specificity, precision, linearity, LOD, LOQ, robustness, accuracy and the expanded uncertainty was also evaluated.