Original Medicare - Parts A and B - covers a lot. But it also leaves meaningful gaps that can add up to significant out-of-pocket costs if you are not prepared for them. Understanding what is not covered is just as important as understanding what is.
This article explains the main coverage gaps in original Medicare and the two primary paths people use to address them. It is the starting point for everything else in our health insurance basics section.
The Gaps That Catch People Off Guard
No Out-of-Pocket Maximum
One of the most significant gaps in original Medicare is something it simply does not have: a cap on how much you can spend in a given year.
According to Medicare.gov, original Medicare has no out-of-pocket limit. That means if you have a serious illness or a difficult year medically, your costs in theory have no ceiling. Part A has a deductible for each benefit period, and Part B has a 20% coinsurance for most covered services - with no upper limit on what that 20% could add up to.
For most people, this is the primary reason supplemental coverage matters.
No Routine Dental, Vision, or Hearing
According to Medicare.gov, original Medicare generally does not cover:
- Routine dental exams, cleanings, fillings, or dentures
- Routine eye exams or prescription glasses
- Hearing aids or the exams to fit them
These are among the most common health needs for older adults, and they are largely outside of what original Medicare pays for. There are some narrow exceptions - for example, Medicare may cover certain dental services directly related to a covered medical procedure - but routine preventive care for teeth, eyes, and ears is generally not included.
Limited Long-Term Care Coverage
Original Medicare does not cover long-term care - the kind of ongoing custodial care in a nursing home or at home that someone might need following a serious illness, injury, or cognitive decline. According to Medicare.gov, Medicare may cover a limited period of skilled nursing facility care after a qualifying hospital stay, but this is specifically for skilled care (rehabilitation, wound care, IV therapy, and similar services), not for custodial or personal care over an extended period.
Long-term care is a separate planning topic and one of the larger financial risks in retirement. It is not addressed by any of the supplemental coverage options described below.
Part B Coinsurance With No Cap
Under original Medicare Part B, you generally pay 20% of the Medicare-approved amount for covered services after meeting your annual deductible. For routine care, this is manageable. For cancer treatment, cardiac procedures, or extended specialist care, 20% of high-cost services can become substantial quickly - and again, there is no upper limit.
What are the two main ways to address Medicare's coverage gaps?
People with original Medicare generally choose between two approaches: adding Medigap (Medicare Supplement Insurance) to original Medicare, or enrolling in Medicare Advantage. Medigap typically offers broader provider access and predictable costs. Medicare Advantage bundles coverage through a private plan, often with added dental, vision, and hearing benefits but with network restrictions.
People with original Medicare generally choose one of two approaches to fill the coverage gaps:
Path 1: Medigap plus a standalone Part D plan. Medigap (also called Medicare Supplement Insurance) is private insurance that works alongside original Medicare to cover some or all of the cost-sharing Medicare leaves to the beneficiary. You keep original Medicare and add Medigap on top of it, then add a separate Part D plan for prescription drug coverage. This path typically offers broader provider access and more predictable costs.
Path 2: Medicare Advantage. Medicare Advantage (Part C) is an alternative to original Medicare offered through private insurers approved by Medicare. Instead of using Parts A and B directly, you receive your Medicare benefits through the Advantage plan. Most plans include drug coverage and often add some dental, vision, and hearing benefits. This path typically involves network restrictions and prior authorization requirements in exchange for potentially lower premiums and additional benefits. One consideration when evaluating Medicare Advantage: most plans require prior authorization for certain services, and documented concerns about denial rates and approval delays are worth researching before choosing a plan.
These two paths are mutually exclusive - you are either on original Medicare with supplemental coverage, or on Medicare Advantage. Each has genuine tradeoffs depending on your health needs, finances, and where you live.
This article is not the place to weigh those tradeoffs - that is a personal decision. Our other articles in this section go into each option in more detail. The important takeaway here is that original Medicare alone leaves meaningful gaps, and most people benefit from understanding those gaps before making decisions about supplemental coverage.
What happens if you have no supplemental coverage with Medicare?
Carrying original Medicare alone without any supplemental coverage means there is no cap on what you could spend in a bad medical year. Some people in good health with savings choose this path, but the absence of an out-of-pocket maximum means a serious illness could result in substantial costs with no defined ceiling.
It is worth briefly noting that some people choose to carry original Medicare alone with no supplemental coverage - particularly people with very low health care use and enough savings to absorb unexpected costs. This can work in some circumstances. But given the absence of an out-of-pocket cap, it carries real financial risk if a serious health event occurs.
Getting Help Navigating the Options
A SHIP (State Health Insurance Assistance Program) counselor can walk you through your options in detail at no cost, without selling you anything. This is often the most useful first step before comparing specific plans. If you are evaluating Medicare Advantage as one of your paths, ask your SHIP counselor specifically about prior authorization practices and denial patterns. These are worth understanding clearly, especially with an eye toward how your needs may change as you get older.
Find your local SHIP counselor at shiphelp.org or by calling 1-877-839-2675.
Also see our related articles:
- Medigap vs. Medicare Advantage: What's the Difference
- What Is Medigap and How Does It Work
- What Is Medicare Advantage (Part C)
- What Is Medicare Part D Prescription Drug Coverage
- Dental, Vision, and Hearing Coverage for Seniors
Coverage details and costs for Medicare and supplemental plans change each year. Visit medicare.gov or speak with a SHIP counselor for current information specific to your situation. A SHIP counselor can give you personalized guidance on Medicare options in your area at no cost. Find yours at shiphelp.org.