Replaces everything after the enacting clause. Amends the Newborn Metabolic Screening Act. Provides that the Department of Public Health shall provide all newborns with a screening test for guanidinoacetate methyltransferase deficiency using a method that determines the presence or absence of the deficiency, beginning on the earlier of July 1, 2021 or within 6 months following the occurrence of specified milestones. Authorizes the Department to adopt emergency rules to implement the amendatory Act. Amends the Illinois Administrative Procedure Act. Makes a conforming change.