What is coinsurance in Medicare and how is it different from a copay?

Think of it this way. A copay is a flat fee. You go to a specialist, you pay $30, done. The amount doesn't change based on what the visit costs. Copays are simple and predictable.Coinsurance is different. It's a percentage of the total cost of a service. Original Medicare uses coinsurance frequently. For example, after you meet your Part B deductible, Medicare typically covers 80 percent of approved outpatient costs and you pay the remaining 20 percent. If a procedure is billed at $1,000, your 20 percent share is $200. If it's billed at $5,000, your share is $1,000. The percentage stays the same, but your actual cost goes up with the price of the service.In Original Medicare (Parts A and B), coinsurance is the norm rather than the exception. Hospital stays under Part A also involve coinsurance after a certain number of days. This is one reason many people add a Medigap plan (supplemental insurance) or choose Medicare Advantage. Both options can reduce or eliminate coinsurance exposure, though they come with their own cost structures.Medicare Advantage plans tend to use copays more than coinsurance, which can make costs easier to predict. But every plan is different, and the details matter. Always review a plan's Summary of Benefits to understand what you'd actually pay for the services you use most.