Humane endpoints are predetermined criteria for ending animal experiments early when animals show signs of severe suffering, and their implementation is one of the most important welfare protections in laboratory animal science.
The shift from death-as-endpoint to defined humane endpoints represents one of the most significant welfare advances in laboratory animal science over recent decades. When death is the experimental endpoint, animals endure the full progression of disease or toxicity before the experiment concludes — a period of intense suffering that is scientifically unnecessary in most cases. Humane endpoints prevent this final phase of suffering while maintaining experimental validity in the large majority of study designs. However, implementation quality varies: poorly defined criteria, inadequate training for animal care staff, or reluctance to end experiments early for scientific reasons mean humane endpoints are not always applied consistently. Institutional culture and training profoundly affect how reliably these protections work in practice.