Humane endpointsHumane endpoint The moment in the experiment at which pain and/or distress experienced by the investigational animal is ended or alleviated by either killing the animal humanely or by discontinuing the procedure. can become relevant when moral, scientific or legal considerations have to be taken into account.

1. Moral considerations:
   • ​the laboratory animal is experiencing more painPain The negative sensory or emotional experience that indicates awareness in the animal of injury or the threat of injury to the body. This negative experience induces changes in an animal’s behavior and physiology, intended to limit the effect of, or avoid the injury, to reduce the chances of repeated injury and to promote recovery., sufferingSuffering A negative emotional state which derives from adverse physical, physiological and psychological circumstances, in accordance with the cognitive capacity of the species and of the individual being, and its life experience., or chronic distressDistress It indicates a disadvantageous environment in which the animal is no longer able to adapt in a biologically successful manner to the stressors to which it is exposed. One speaks of distress when the level or the duration of stress are such that significant changes in biological function are required to survive. than can be justified;
   • the animal is no longer able to perform important activities and behaviors due to pain or distress.
2. Scientific considerations:
   • the scientific objectives of the experiment have been met and keeping the animal in experiment has no additional value to the results of the study, or may even interfere with the results;
   • it is clear that the objectives of the experiment cannot be met;
   • keeping the animal alive may lead to loss of data (for instance, when the animal dies in the cage it may be autolytic when going for pathology or it may be cannibalized by cage mates).
3. Legal considerations:​
   • ‘Member States shall ensure refinementRefinement The principle of limiting or reducing the severity of scientific procedures by treating laboratory animals in such a way that potential pain, distress and other deleterious effects inflicted on the animals are avoided, alleviated, or minimized. It may also be a way in which their welfare can be improved e.g., through enrichment of their husbandry. In laboratory animal care, Refinement is known as one of the 3Rs in the Three Rs ethical framework. of breeding, accommodation and care, and of methods used in procedures, eliminating or reducing to the minimum any possible pain, suffering, distress or lasting harm to the animals’ (Council Directive 2010/63/EU, art.4.3.);
   • ‘Death as an endpoint to a procedure shall be avoided as far as possible and replaced by earlier and humane endpoints. Where death as the endpoint is unavoidable, the procedure shall be designed so as to:​
     • result in the death of as few animals as possible; and
     • reduce the duration and intensity of suffering to the animals to the minimum possible and, as far as possible, ensure a painless death‘ (Council Directive 2010-63-EU, art.13.3).