We developed and implemented a decision support system for prescribing parenteral nutrition (PN) solutions for infants in our neonatal intensive care unit. We employed a graphical user interface to provide clinical guidelines and aid the understanding of the interaction among the various ingredients that make up a PN solution. In particular, by displaying the interaction between the PN total solution volume, protein, calcium and phosphorus, we have eliminated PN orders that previously would have resulted in calcium-phosphorus precipitation errors.