How does Medicare Part A coordinate with my employer group health plan?
I am over 65, have employer insurance, and Medicare Part A. Will Medicare Part A pay for hospitalization in addition to my employer insurance?
Yes, Medicare Part A will pay part of your hospital bills even if you also have work-related insurance. Which coverage pays first -- Medicare Part A or your private, employer-sponsored insurance -- and how much each pays depends on the size of your employer. If your employer has 20 or more employees, then your employer-based health plan is the primary payer, with that insurance paying first and Medicare Part A paying some of the remaining costs. If your employer has fewer than 20 employees, Medicare would be the primary payer of your hospital bills, in which case your private, employer-sponsored health insurance would pay some of the costs that Medicare doesn't pay (like the Medicare Part A hospital deductible and copayments).
If and when you register for a hospital stay, give the hospital registrar your Medicare card and also the information about your employer-sponsored insurance. The hospital will then automatically submit your bills to both, and Medicare and the private insurance company will sort out between them which insurance pays how much of the bills. To read more about how Medicare and private insurance pay in these situations, you can look at Medicare's online booklet Medicare and Other Health Benefits: Your Guide to Who Pays First.
Quirks in primary payment can invalidate part A coverage when Medicare is secondary. For example, you have a hospital event fully or mostly covered by a primary employer plan except for an unmet primary deductible. If the primary plan pays the hospital doctors (not a part A expense) before the hospital bill the entire primary deductible may be used for doctors. When the hospital is paid afterward, there's no deductible left and the beneficiary gets little or no benefit from having Part A . If your primary plan is a high deductible plan, this could cost you thousands.
In addition,as noted in a previous answer, if your employer is small, Medicare may be primary. It is then possible, depending on details in the employer plan (ask Human Resources,) that your work insurance will limit coverage unless you have both Part A and Part B.