The answer depends on what type of Aetna Medicare Plan you have. If you have an Aetna Medicare Supplemental Plan, then Original Medicare pays first and the Aetna plan pays secondaryIf you have an...
When you are on a private health plan.
It's much more complicated than that. The most common reason is that you're not retired so your employer is prime.
If you have a Medicare Supplement then the provider will bill Original Medicare first. At that time Medicare will pay the allowable amount and then return an explanation of benefits stating the...
This is directly from the Medicare and You 2009 Book:
When you have other insurance, there are rules that decide whether Medicare or your other insurance pays first. The insurance that pays first is...