Checking my last day of health coverage - 5 weeks in

I was told my coverage ends on my last day, but the letter says the end of the month. I have read a lot of threads here and could not find my exact situation. The letter is unclear about dental and vision. What should I do about appointments?

Dental and vision sometimes end on a different date from medical. Mine did.

Keep a copy of any coverage confirmation in case of later disputes.