The four main gaps Medicare leaves behind

Original Medicare (Part A and Part B) covers hospital stays, doctor visits, and some medical equipment, but it leaves four significant gaps: prescription drugs, dental care, vision care, and hearing aids. These are not small omissions. A single pair of hearing aids can cost $4,000 to $6,000 out of pocket. A year of prescription medications for a chronic condition can run into thousands of dollars. Original Medicare does not cover any of these.

The gap you face depends on which type of coverage you choose. If you stay with Original Medicare, you can buy a Medigap policy (also called supplemental insurance) to cover some costs Medicare does not pay — but Medigap does not cover drugs, dental, vision, or hearing. If you switch to a Medicare Advantage plan, you get drug coverage built in, and many Advantage plans also include dental, vision, and hearing benefits. The trade-off is that Advantage plans have networks, copays, and prior authorization requirements that Original Medicare does not.

Key Takeaways

  • Original Medicare does not cover prescription drugs, dental care, vision care, or hearing aids — these are the four main gaps.
  • Medigap policies fill some gaps in what Medicare pays for covered services, but they do not cover drugs, dental, vision, or hearing.
  • Medicare Advantage plans include prescription drug coverage and often add dental, vision, and hearing benefits, though they require you to use in-network providers.
  • You must choose a separate Part D plan for drugs if you use Original Medicare and Medigap, or your Advantage plan's drug coverage is automatic.
  • The best choice depends on whether you take many medications, need dental work, wear glasses or hearing aids, and how much you are willing to pay upfront versus at the doctor's office.

How Medigap addresses gaps in Original Medicare payments

Medigap policies are sold by private insurance companies and are designed to pay the costs that Original Medicare leaves you responsible for. These include the Part B deductible (the amount you pay before Medicare starts paying), copays for doctor visits, coinsurance for hospital stays, and excess charges that some doctors bill above Medicare's approved amount.

The ten standardized Medigap plans are labeled A through N, and each covers a different combination of these gaps. Plan G, for example, covers the Part B deductible, copays, coinsurance, and excess charges — but not prescription drugs. Plan N covers most of the same things but has small copays for doctor visits and emergency room visits. No Medigap plan covers dental, vision, hearing, or drugs, no matter which letter you choose.

Medigap premiums vary by insurance company and by your age and health history at the time you enroll. If you buy Medigap during your initial enrollment window (the six months after you turn 65 and enroll in Part B), insurers cannot deny you or charge more based on pre-existing conditions. If you wait, some companies can refuse to sell you a policy or charge significantly more.

What Medicare Advantage plans include that Original Medicare does not

Medicare Advantage plans (also called Part C) are an alternative to Original Medicare. They are run by private insurance companies but must cover everything Original Medicare covers. The difference is that most Advantage plans add benefits that Original Medicare does not: prescription drug coverage, dental care, vision care, hearing aids, and sometimes fitness programs or meal delivery.

The scope of these added benefits varies widely. Some Advantage plans cover routine dental cleanings and exams but not major work like crowns or root canals. Some cover eye exams and glasses but cap the benefit at $150 per year. Some cover hearing aids but only up to $1,500 per ear, and only from in-network providers. You need to read the specific plan's benefit document to know what is actually covered and what you will pay out of pocket.

The catch is that Advantage plans use networks. You must see doctors and dentists in the plan's network, or you pay more or nothing is covered at all. Most Advantage plans also require prior authorization — the plan must approve a service before you receive it, or it may not pay. And Advantage plans have annual out-of-pocket maximums, which means your total costs are capped, but you could hit that cap quickly if you need a lot of care.

Prescription drug coverage: Part D with Original Medicare or built into Advantage

If you choose Original Medicare and Medigap, you must buy a separate Part D prescription drug plan. Part D is sold by private insurance companies and covers both brand-name and generic drugs, though not all drugs are covered and costs vary by plan. You choose a Part D plan during your initial enrollment window or during the annual open enrollment period in October and November. If you do not enroll when you are first may be able to access and you do not have other drug coverage, you pay a penalty for every month you go without it — even if you do not take any medications.

If you choose a Medicare Advantage plan, prescription drug coverage is usually included. You do not buy a separate Part D plan. The Advantage plan's formulary (the list of covered drugs) may be different from other plans' formularies, so if you take specific medications, you need to check whether they are covered before you enroll.

Dental, vision, and hearing coverage by plan type

Original Medicare covers dental only in very limited situations — for example, if you need teeth removed before radiation therapy for cancer. It does not cover routine cleanings, fillings, crowns, or dentures. Original Medicare covers vision only for eye exams after cataract surgery or for people with diabetes or macular degeneration. It does not cover routine eye exams or glasses. Original Medicare does not cover hearing aids at all, though it does cover hearing exams.

Medigap policies do not fill these gaps. None of the ten Medigap plans cover dental, vision, or hearing. If you use Original Medicare and Medigap, you pay for these services out of pocket, or you buy separate dental and vision insurance on the private market.

Medicare Advantage plans often include dental, vision, and hearing benefits, but the coverage is limited and varies by plan. A plan might cover one dental cleaning per year but charge you $50 per visit. Another might cover glasses every two years but cap the benefit at $100. Some plans cover hearing aids but only from specific manufacturers or only up to a certain dollar amount per ear. You need to compare the specific benefits in each plan you are considering, not just assume that "dental included" means your dental care is covered.

Comparing costs: premiums, copays, and out-of-pocket limits

The total cost of coverage depends on three things: the monthly premium you pay to the insurance company, the copays and coinsurance you pay when you use care, and your annual out-of-pocket maximum (if the plan has one).

Original Medicare has no monthly premium for Part A (if you or your spouse paid Medicare taxes for at least ten years) and a monthly Part B premium that increases each year based on your income. You also pay a deductible and coinsurance for each service. If you add Medigap, you pay a monthly Medigap premium on top of your Part B premium. If you add Part D, you pay a monthly Part D premium. Many people on Original Medicare with Medigap and Part D pay $200 to $400 per month in premiums alone, plus copays when they see a doctor.

Medicare Advantage plans have a monthly premium (which can be $0 for some plans in some areas) and copays for doctor visits and other services. Most Advantage plans have an annual out-of-pocket maximum — once you reach it, the plan pays 100 percent of covered services for the rest of the year. This maximum varies by plan but is capped by Medicare at a certain amount each year. If you use a lot of health care, hitting the out-of-pocket maximum can actually save you money compared to Original Medicare with Medigap.

How to decide which gaps matter most to you

Start by listing what you actually use. Do you take multiple prescription medications? Do you wear glasses or contact lenses? Do you wear hearing aids or think you might need them soon? Do you have dental work that needs to be done? Do you see a dentist regularly? The gaps that matter are the ones that affect your life.

If you take many medications or expect to, Part D coverage (through Advantage or a separate plan) is essential. If you wear glasses or hearing aids, an Advantage plan with those benefits will likely save you money over buying them out of pocket. If you have chronic conditions and see multiple specialists, check whether your doctors are in the Advantage plan's network before you enroll — if they are not, Original Medicare with Medigap may be better for you even if it costs more upfront.

You can change your choice once a year during the annual open enrollment period in October and November. If you make the wrong choice, you are not stuck with it forever. But switching plans means new deductibles, new networks, and new formularies, so it is worth getting it right the first time if you can.

Frequently Asked Questions

Can I use Original Medicare and buy dental insurance separately instead of switching to Advantage?

Yes. Dental insurance sold on the private market is separate from Medicare and can be purchased at any time. These plans typically have waiting periods (three to twelve months) before they cover major work like crowns, and they have annual maximums, often $1,000 to $1,500 per year. They are usually cheaper than Advantage plans if you only need routine care, but more expensive if you need major work done.

If I choose Advantage, can I go back to Original Medicare later?

Yes, but only during specific windows. You can switch back during the annual open enrollment period (October 15 to December 7) or during the Medicare Advantage open enrollment period (January 1 to March 31). If you switch back to Original Medicare, you can buy Medigap, but insurers can charge you more or deny you coverage if you do not enroll during your initial six-month window after turning 65.

Do all Medicare Advantage plans include drug coverage?

Almost all do, but a small number of Advantage plans do not include Part D. If you are looking at an Advantage plan without drug coverage, you would still need to buy a separate Part D plan. These plans are rare, but you should always check the plan document to confirm whether drugs are included.

What happens if my doctor is not in my Advantage plan's network?

You can still see that doctor, but you will pay more — usually the full cost of the visit, or a much higher copay than in-network providers. Some Advantage plans allow out-of-network care in emergencies or for certain specialists if no in-network provider is available, but you need to check your specific plan's rules. Before you enroll in an Advantage plan, call your doctors' offices and ask whether they accept that plan.

Do I have to choose a plan during open enrollment, or can I enroll anytime?

You can enroll anytime during the annual open enrollment period (October 15 to December 7 each year), and your coverage starts January 1. If you are newly may be able to access for Medicare (turning 65 or losing employer coverage), you have a special enrollment window of about two months. Outside these windows, you cannot change plans unless you have a may have access to life event like moving out of your plan's service area or losing other health coverage.