In-laws and dealing with dementia?

I am so sorry to hear of your situation and that of your in laws. It is time to talk to them about getting some home health care, especially for your mil. I would first call her doctor (or their office, they may have someone who handles this sort of thing) and let them know that she is not able to remember to check her blood sugar. Technically that is a life threatening situation for her, and it should be what it takes to get the ok for a home health nurse to come in and help her care for her husband and herself at the very least.

Then, talk to a lawyer and find out what your options are. There are options such as Medical Power of Attorney that allows you to take the helm so to speak should either of them become unable to manage their affairs. Most people are ok with that. Also, you all need to talk about living wills, etc. with them anyway. It is a tough thing to get people to talk about and do because it means facing mortality and becoming incapable, and no one likes to think of it, much less actively deal with it, even when we are of sound mind...

So, call her doctor let them know what is happening, then call and make an appt with a lawyer who has experience in this area. Have all your questions and concerns written out ahead of time so you don't forget anything. When you are fully armed with information and you know your options, then it is time to approach them. The best way to get people to cooperate when you want to help them is to tell them that you are only doing this to help them, and they you want to help them remain in their homes and healthy. Becoming less independent has got to be scary and of course they want to fight against anything that threatens that. I do not envy you your battles ahead.

Blessings and good luck!

Edit: I forgot to add, you also want to check your MIL's medication. Sometimes people can take multiple medications that can interact with each other and cause the person to have demetia like side effects. This is especially common in elderly people who may have many physcians who are not aware of all the medicines that a particular patient is on. I strongly suggest you get a list of all medications both of your in laws are on and review them with their doctors to make sure that they are compatible and necessary!