What factors influence the choice of euthanasia method for mice?

• A. Only age matters.
• B. Only institutional SOPs matter.
• C. Only the preferred researcher preference.
• D. Age, health status, experimental requirements, and institution SOPs; methods should be validated and humane.

Answer: (D)

Choosing a euthanasia method for mice depends on multiple interacting factors to ensure both humane treatment and data integrity. Age affects what method is practical and how the animal tolerates the procedure; very young or very old mice can respond differently and may require adjustments to technique or settings. Health status matters because illness, weakness, or specific medical conditions can alter response, contraindicate certain methods, or affect the time to death and level of distress. Experimental requirements must be considered so that the chosen method does not confound results or interfere with downstream analyses, tissue preservation, or timing of endpoints. Institutional SOPs provide the framework for approved methods, training, equipment, monitoring, and regulatory compliance, and they require method validation to confirm it reliably and humanely achieves death in the facility’s specific strains, ages, and conditions. When all these factors are taken into account and the method is validated, you achieve humane, consistent euthanasia that fits the study’s needs and the institution’s standards.