Not necessarily. It depends on which homeostatic process is lost: organisms usually exhibit a range of different homeostatic processes, such as maintenance of blood pressure, maintenance of body temperature, maintenance of water potential in plants, of reaction network function, and so on. This is why an organism can lose homeostasis in terms of blood pressure, temperature etc. but so long as the molecular network within cells retains function the physiological (large-scale) processes can be restarted and the organism can be revived. So, the reason why mouth-to-mouth and cardiopulmonary resuscitation work is that despite loss of physiological homeostasis, the underlying reaction networks are still functioning within the neuron cells of the brain (i.e. death has not occurred despite an evident loss of physiological homeostasis). If homeostasis cannot be restored in the physiological function, brain death then occurs specifically when the neuron reaction networks (cellular processes) lose homeostasis. Scale is key to understanding life and death, and the fundamental processes occur at much smaller scales than we usually consider in our every-day lives. Death is loss of homeostasis, but specifically loss of homeostasis in self-regulating networks of molecules that change conformation in a way that directs thermodynamically-driven motions to do work.

Isn't life an ability? To respond.