Monensin is an ionophore widely used in the dairy cattle industry throughout the world. A large volume of clinical trials have been conducted that have explored efficacy for various metabolic, production, and health outcomes. However, the results of the individual studies have in some cases been contradictory and in others inadequately sized to fully address the objectives particularly for health and production. The meta-analysis of monensin dairy data illustrates an example of the power of this tool for helping to make evidence-based decisions for health management and production consultants. Its importance and utility will continue to grow in future years.