My father's fingernails have gotten quite long and need to be cut. He can be belligerent and I am afraid to cut them. Any suggestions?

My dad is cognitively different, but not dementia. I used to tell him in a calm voice that it was time to cut his nails, no biggie, but just a matter-of-fact issue. I would have to catch him in the right mood. I'd just whip through a quick trim down and that was that. I suppose it all depends on the "patient." If your dad is agitated all the time, then Barb is right -- consider medicating him for his sake, and also for you and caregiver to be able to care for him.

And... if agitation is the issue why he's resistant to cutting his nails, a visit to a doctor for this reason could go very badly.  If your dad is the type that "showtimes" for a doctor, then maybe this won't be the case, but it's hard to say how a typically agitated elder would act for a new doctor who wanted to cut their nails (an activity they don't like).  

If he is suffering from agitation, you should talk to his doctor about meds.

Cut them when he’s asleep?

You can ask the doctor but I don't think he would. I had no problem with Mom. Bumping u up.