Retirement comes with its own set of questions and things to look out for, especially with health insurance coverage for individuals who are eligible for Medicare. Retiree insurance coverage offered by a former employer or a retiring spouse’s employer is not a mandatory benefit, and the sponsoring employer may change premiums and benefits or cancel the plan entirely based on their internal needs. If you have group insurance from a retiree plan along with Medicare coverage, Medicare provides primary coverage and your employer-sponsored insurance is secondary. You are, however, responsible for the premiums on your retiree group plans and your Medicare coverage. The cost and coverage varies from company to employee, depending on which package is offered.