My elderly mother in law has started to get up frequently during the night to check everyone is in bed. Should I be concerned?

Your profile says she has Dementia/ALZ so this is normal.

Depending how far along she is, in her mind she maybe checking on her children. 3 am seems to be a usual time for people suffering from a Dementia to get up. My Mom did it too. She thought it was time to get up. And would start getting dressed. I would have to show her it was dark out so not time to get up. She would say OK and go back to bed.

My mom did that frequently, no it isn't safe. What if one night she does not check on everyone and decides to take an evening stroll instead. What security measures do you have in place? Locking her in her room is not an option. And yes get her checked for a UTI.

Motion detectors? Alarms? Baby monitor?

Since you say she doesn't remember that's she done it multiple times a night, yes I would be concerned. She is young to be having dementia symptoms. Maybe she should be checked for a UTI and have a cognitive exam, this way you'll know what you're dealing with. Also, getting up in the night puts her at risk for falling (especially if she is frail or unsteady on her feet). Maybe you can put a sign on the inside of her door telling her everyone is ok and not to leave her room? If she has dementia you won't be able to correct her behavior as she won't remember. Also this behavior means she may not be getting quality sleep (and soon you won't be, either). I would get her in for testing as soon as you are able.

MIL appears worried about all of you and checking on you makes her feel more secure. I would not be too worried at this point. My mother calls me sometimes when she is in bed to make sure I am home, and she is not alone.

Rosie50, sounds like your Mom may have heard about the C-19 virus, thus she wants to check on everyone to make sure they are ok.

Please note, when someone has dementia you cannot reason with that person because their brain is, unfortunately, not thinking clearly. So sorry you are going through this since your Mom is so young by today's standards.