Mom's dementia has suddenly gotten much worse. Can this actually happen?

Since your mother lives in AL, they should be able to test her for a UTI right there. A blood test should also be available to see if her white blood count is elevated indicated an infection somewhere in her body which could contribute to her confusion, as the others have said. My mother's AL has a traveling medical company that comes in to draw blood & have it tested. Hearing problems can also lead to 'hearing voices', so don't rule that out, esp if mom's hearing has been declining lately. A visit to the ENT doctor might not be a bad idea if all else fails.

Once infection and/or UTI is ruled out, yes, dementia can indeed worsen suddenly. The person can take a 'step down' from one day to the next and become entirely different with regard to behavior. I've seen it with my mother who has moderately advanced dementia, although she is not hallucinating or hearing voices *yet*. Getting memories all mixed together IS something that she suffers from, however. It's making her more depressed and angrier than usual, so her doctor is coming in on Tuesday to check her out & do a med evaluation (she lives in Memory Care AL).

Here is a good article on the subject, along with coping techniques:

https://www.alz.org/help-support/caregiving/stages-behaviors/hallucinations

Wishing you the best of luck getting to the root of the problem with your mom. I know how hard all of this is.

"Suddenly" usually = UTI. Does she have a fever? (another symptom of UTI). Even if no, I would not wait to bring her in to get started on antibiotics, if that's the therapy prescribed.

I agree she needs to be tested for a UTI. If that is not the problem, then she may need something to help with the hallucinations. She could have just gone into the next stage.

I am glad you are getting your mom tested. My mother has side effects simular to yours. My mother suddening gets worse with a UTI. After treatment she is usually back to baseline. Early intervention is best. I would get right on it immediately. Good luck

If she's already been awake for 24 hours and she's still having hallucinations, I'd be inclined to treat this as an emergency and not wait to get her urine checked. I can understand if you'd rather not take her to the ER, but isn't there a pharmacy or a walk-in centre open anywhere near you today? Certainly I think it would be better if you can get medical advice, at least.

Infection somewhere causing delerium would be my 1st guess - UTI or chest infection being main culprets.

Sleeplessness can cause mania behaviour.

Yes, seek medical help to rule some things out.