How long can my mum, who has dementia, survive without food and limited fluid? She has insulin diabetes.

I see that your mom also has Alzheimer's and has been in the NH. Is she on hospice? I think how long she can survive is an unknown based on the information you have shared. People can live a very long time without food as long as they have water. But a person who is shutting down might not live a day. Is she comfortable? Are you okay? Give us a bit more information.