It is important to understand when your Medicare Coverage is your primary payer and when it is your secondary payer. This is because if it is your primary payer it will cover more of your costs. If it is your secondary payer it will only pick up the slack where your insurance company does not cover you.
If you are over sixty five and are working with a Group Health Plan, than your Medicare coverage may be your primary provider, depending on how many employees are working for your employer. If there are twenty or more employees, than Medicare counts not as your primary provider, but as your secondary provider. This is only if you are still working. A retiree plan is not considered a Group Health Plan. Depending on your the coverage provided by your retiree plan, you might not be eligible for Medicare. If you are, than Medicare will be your primary provider.
If you are receiving Medicare coverage because you are on disability, you are employed, and you have a Group Health Plan, than your employer will be the primary payer only if there are a hundred or more employees that work for them. If there are fewer, than Medicare will be your primary payer and they will cover more of your expenses.
Your employer will be the primary payer for the first thirty months that you are eligible for Medicare, after which Medicare will become your primary payer.
If you have personal injury insurance, they will pay first, and Medicare will pay second.
If you had COBRA before you became eligible for Medicare coverage, than COBRA will be terminated when you go on Medicare. If on the other hand you had Medicare first, than you will receive assistance from COBRA but Medicare will remain your primary provider. If you are under the age of sixty five and on Medicare COBRA will remain your primary payer.