You enrolled in Original Medicare, added a Medicare Supplement policy, and probably expected the stream of medical bills to slow to a trickle. Then an envelope arrives saying you owe $283, another bill appears after a doctor’s appointment, or you’re charged for something you thought your supplement covered. That doesn’t necessarily mean somebody made a mistake, because Medigap is designed primarily to help with certain out-of-pocket costs for services Original Medicare covers, not to turn every healthcare service into a $0 expense. Here’s what every beneificary needs to know about medical bills with Medicare and Medigap.