Introduction Pharmaceutical treatment in the neonatal intensive care unit (NICU) is challenging, and newborns are often exposed to numerous different medicines during their hospitalization There is currently insufficient knowledge of gestational age dependent medicine disposition, and accordingly the use of off-label medicines, i.e., use of medicines outside its approved marketing authorization, is high. This study aims to estimate the off-label medicine use in Danish neonatal departments. Methods By using data from the Danish National Pharmaceutical Hospital Purchase Database, we identified the most commonly occurring medicines and calculated the on/off-label ratios for premature and term neonates. Data was extracted on ATC level 5 and based on defined daily doses as per WHO. Results Data included was covering the 4 high-level NICUs and 10 of 13 of the intermediate/standard level neonatal departments in Denmark. Of the identified medicines, 87% and 70% did not have approved marketing authorization for use in premature and full-term neonates, respectively. Furthermore one-fifth of the top 100 medicines did not have a (Danish) marketing license. Overall, the presence of off-label medicines was widespread covering virtually all ATC groups and no ATC group had an off-label level lower than 50%. Finally, in 21% of the identified medicines, additives from 8 different chemical groups with potential deleterious effects for neonates were identified. Conclusion Off-label medication in the Danish neonatal departments is widespread, and the current state of neonatal official regulatory drug approval leaves both patients and neonatologists in a limbo between legal pharmaco-regulation and clinical need for pharmacotherapy in neonatology.