My hubby, whois 77, had 2 episodes of forgetfulness. Thought our dog was one he had yrs ago. I think his sugar level is high. He has grandson and great grandkids long distance. We only see once a yr or 2. He said he met the last grandson already. I said no, he swore he was right. Finally he realized he was wrong. Should I be worried? Everything else perfectly normal.
You say you think his blood sugar is high. Does he have diabetes? Hypoglycemia or Hyperglycemia can cause strange reactions in people. There are people more knowledgeable than me who will probably give you better answers.
I would take him in to see the Doc. Better safe than sorry.