OBJECTIVE: To evaluate the impact of a compulsory pop-up form on the ordering pattern of proBNP blood tests by general practitioners in the Capital Region of Denmark. DESIGN: A follow-up study comparing the average number of proBNP tests ordered before and after the implementation of an intervention. SETTING AND SUBJECTS: From 2016 to 2021, the average number of proBNP tests increased by over 300%. In March 2022, a compulsory pop-up form was introduced in the electronic request system (WebReq), requiring general practitioners to select one of three indications for ordering proBNP, as recommended by the Danish Society of Cardiology. The study included 528 general practitioners in the Capital Region of Denmark, with data available from January 2020 to 2023, encompassing 83,576 proBNP results from 56,645 patients. MAIN OUTCOME MEASURE: The average number of proBNP tests ordered per month and the median level of proBNP before and after the intervention. RESULTS: Following the intervention, the average number of proBNP tests per month decreased by 60% over a 22-month follow-up period. The highest reduction was seen among general practitioners who previously ordered the most tests (≥3 per 1000 biochemical tests). In this group, the median proBNP level increased from 12.1 pmol/L before the intervention to 13.5 pmol/L after the intervention ( CONCLUSIONS: This study demonstrates a significant decrease in the number of proBNP requests from general practitioners in the Capital Region of Denmark after the introduction of a pop-up form in the requisition system containing the current guidelines.