Abstract: A system and method for informed prescribing implements a multiplex assay system to measure each of a plurality of chemical entities associated with a patient from a single body fluid sample, and identifies medication levels for each of the measured chemical entities relative to respective target ranges. A drug interaction program module such as a neutral network engine is iteratively trained using the identified medication levels and historical patient data from data storage. Program engines further measure an effectiveness of each of the chemical entities with respect to the historical patient data, and generate a recommended dosage for each of the plurality of chemical entities based on a drug interaction output from the drug interaction program module and the measured effectiveness. A user interface displays the results, and in an embodiment further provides alternative treatment options with respect to certain chemical entities based on drug interactions and/or effectiveness.