When Is Medicare Primary Or Secondary? 
The factors that determine whether Medicare is primary or secondary are involved . E.g. For a business that has over 20 employees eligible for health insurance , Medicare is usually primary for those age 65 and older . If the business has under 20 employees , the employer 's plan is primary . You can go to this website to find out if Medicare is primary or secondary payer in your situation . WEBSITELINK . You could also call 1-800-MEDICARE to ask about specific situations . 