It can be difficult and frustrating if your loved one isn’t acknowledging or accepting that they have dementia. This could be something they’re doing on purpose because they feel it’s embarrassing, or they may simply lack insight.
You should approach your concerns in a gentle and supportive manner. Keep a diary of events, so that you can back up what you’re saying with examples. Make sure you’re showing concern, and not that you’re spying on them.
Encourage your loved one to see a doctor. You can do this by appealing to their compassion. Say something like “it could get us some support that might help me understand some changes I’m seeing…”. If this fails, you can consider speaking to their doctor yourself.