What Does Medicare As Secondary Cover? 
Having two health insurance programs generally happens when a person is eligible/signed up for Medicare Part A -LRB- premium-free -RRB- , but is still working and has group health insurance coverage through their employer . When this happens and the group coverage pays first and Medicare pays second , the group coverage will pay its share and whatever the balance is will go through the Medicare 's claims department - Medicare will pay their share up to the Medicare-approved amount . You will be responsible for paying any remaining balance after that . Most of the time if you 're paying for Medicare Part B , you 're not going to be paying for group coverage as well - you would either have group coverage + Medicare Part A or Medicare Part A + Part B . If you 're on Medicare Parts A & B , I highly recommend adding a Medicare supplement -LRB- Medigap -RRB- policy to help cover the gaps in coverage provided by Original Medicare -LRB- Parts A & B -RRB- . 