In 2023, the General Directorate of Pharmacy of the Ministry of Health commissioned the Advisory Committee on the Financing of Pharmaceuticals for the National Health System (CAPF, Comité Asesor para la Financiación de la Prestación Farmacéutica del Sistema Nacional de Salud) to produce a guideline for the evaluation of the efficiency of medicines. The aim of this methodological note is to present their main points. The guideline includes 17 dimensions that an economic evaluation of medicines must encompass, the design of a reference case, and a checklist for evaluating the methodological quality and reporting. This guideline should serve as a foundational document for reforming the health technologies evaluation processes of the Ministry of Health. The guideline can also assist researchers, public health professionals, health technology companies and decision makers in assessing the validity of findings and conclusions from health economic evaluations.