The culture of evidence-based practice includes also the field of laboratory medicine. Clinical laboratory expenditure is growing rapidly for various reasons including increased utilization. Delivering decision support to requesters at the point of care is one of the main incentives for implementing laboratory guidelines. Laboratory guidelines were analyzed to extract test-ordering rules. Each rule was explicated in at least one clinical situation with triggers that launch the execution of the implemented rule. The Unified Modeling Language was used to represent the categories of information elements found in the guidelines and underline the information elements that need to be structured and coded in the EHR. These information elements are related to conditions including clinical conditions, habits, family history, demographic information, medical treatments, laboratory tests, and non-laboratory test procedures. Timestamping of each event is also important for implementing laboratory prescription rules. A linkage between the conditions of this model and HL7 RIM was feasible. Use of this model facilitates the implementation of evidence-based test-ordering rules and clarifies the EHR requirements for successful implementation of guidelines.