Call 1-866-309-1719 to reach Medicare Plus Blue Provider Inquiry; Call 1-800-676-BLUE (2583) if you are unsure of your patient's health plan; How to determine dental eligibility and benefits. Call 1-844-876-7917, 8 a.m. to 7 p.m., Eastern time Monday through Friday; Automated information is available 24/7 and via portal provideraccess ....