Medicare has four main coverage gaps, and different plans address different ones

Medicare Part A covers hospital stays and Part B covers doctor visits, but neither covers prescription drugs, dental work, vision care, or hearing aids. Medigap plans, Medicare Advantage plans, and Part D coverage each fill different gaps — and you cannot use all three at once. Understanding which gap each option addresses helps you choose what actually matters to your situation.

The four gaps are: prescription drug costs, dental and vision care, hearing aids, and out-of-pocket costs for services Medicare does cover. A single plan cannot solve all four. Most people address the drug gap with Part D, then choose either Medigap (which lowers your costs for covered services) or Medicare Advantage (which bundles drug coverage and often includes dental and vision). Hearing aids remain the hardest gap to fill — Medicare covers none of it, and most plans do not either.

Key Takeaways

  • Medigap plans lower your out-of-pocket costs for hospital stays, doctor visits, and skilled nursing care, but do not cover drugs, dental, vision, or hearing aids.
  • Medicare Advantage plans usually include prescription drug coverage and often add dental and vision benefits, but have network restrictions and higher out-of-pocket maximums than Medigap.
  • Part D prescription drug coverage is separate from both Medigap and Advantage, and you must enroll during specific windows or pay a penalty.
  • Hearing aids are not covered by any Medicare plan or Medigap option, though some Advantage plans offer limited hearing aid discounts.
  • You choose either Medigap or Advantage, not both — mixing them wastes money and creates coverage conflicts.

What Medigap plans cover and what they leave uncovered

Medigap (also called Supplement insurance) pays the coinsurance, copayments, and deductibles that Original Medicare leaves you responsible for. If Medicare covers a service at 80 percent, Medigap covers the remaining 20 percent. This directly addresses the gap of out-of-pocket costs for hospital stays, doctor visits, and skilled nursing facility care.

Medigap does not cover prescription drugs, dental care, vision care, hearing aids, or long-term care. If you choose Medigap, you must buy Part D separately to cover drugs. Dental and vision remain your own expense unless you buy a separate dental or vision plan outside Medicare — these are not part of any Medigap policy. Hearing aids are not covered anywhere in the Medicare system, so Medigap cannot fill that gap.

Medigap plans are lettered A through N. Plan G and Plan N are the most common for new enrollees. The letter determines what the plan covers; the insurance company determines the price. Two Plan G policies from different insurers cover identical benefits but may cost $50 or $150 per month apart. You can switch between Medigap plans once per year during open enrollment, though some states allow switching anytime.

What Medicare Advantage plans include and exclude

Medicare Advantage (Part C) bundles Parts A, B, and D into one plan run by a private insurance company. Most Advantage plans include prescription drug coverage built in, so you do not buy Part D separately. Many also add dental and vision benefits — typically covering cleanings and exams, sometimes covering basic procedures, rarely covering major work like crowns or root canals.

The trade-off is network restriction and higher out-of-pocket limits. You must use doctors and hospitals in the plan's network, except in emergencies. Your out-of-pocket maximum (the most you pay in a year) is capped by Medicare, but it is usually higher than what you would pay with Original Medicare plus Medigap. Advantage plans do not cover hearing aids, and the dental and vision benefits are limited — a cleaning may be covered, but a crown or new glasses frames may not be.

Advantage plans change their benefits and networks every year. A plan that covered your dentist in 2024 may not in 2025. You can switch to a different Advantage plan or to Original Medicare during the annual enrollment period (October 15 to December 7), but not in the middle of the year unless you have a may have access to life event.

Prescription drug coverage: Part D and how it fits with other plans

Part D is prescription drug coverage only. If you have Original Medicare and Medigap, you must buy Part D separately or pay a penalty for every month you delay. If you have Medicare Advantage, Part D is usually included — you do not buy it separately, and you do not pay a penalty.

Part D plans vary widely in which drugs they cover, what you pay, and which pharmacies you can use. The same drug can cost $10 at one pharmacy and $40 at another under the same plan. You can switch Part D plans once per year during open enrollment, even if you keep the same Advantage plan. If you take expensive medications, comparing Part D plans by your actual drug list (not by star ratings) is the only way to find the lowest cost.

If you go without Part D for more than 63 days in a row, you pay a permanent penalty — roughly 1 percent of the national average Part D premium per month of delay. This penalty stays with you for life, even if you later enroll. The penalty is added to your Part D premium each month.

Dental and vision: what Medicare covers and what it does not

Original Medicare covers neither dental care nor vision care. Medigap does not add dental or vision coverage. Medicare Advantage plans often include dental and vision, but the coverage is limited and varies by plan.

A typical Advantage dental benefit covers two cleanings per year and one exam per year at no cost. A filling may be covered at 80 percent. A crown, root canal, or extraction may not be covered at all, or may be covered at 50 percent with a yearly maximum of $500 or $1,000. Vision coverage usually means one eye exam per year and a discount on glasses or contacts, but not a new pair of frames every year.

If you have Original Medicare and Medigap, you can buy a separate dental plan or vision plan from a private insurer — these are not part of Medicare. Costs vary widely. Some people find that paying out-of-pocket for routine cleanings and exams is cheaper than buying a separate plan. Others with ongoing dental work find a plan worth the cost.

Hearing aids: the gap no Medicare plan fills

Medicare does not cover hearing aids, hearing exams for the purpose of fitting hearing aids, or hearing aid repairs. Medigap does not cover hearing aids. Original Medicare Advantage plans do not cover hearing aids.

Some Medicare Advantage plans offer a hearing aid discount — typically 20 to 30 percent off retail price at participating providers. This is not coverage; you still pay the full cost after the discount. A hearing aid costs $1,000 to $6,000 per ear, so a 30 percent discount saves $300 to $1,800 per ear, but you pay the rest yourself.

If hearing aids are important to your budget, check whether your Advantage plan includes a hearing aid discount and which providers participate. If you have Original Medicare and Medigap, you have no hearing aid benefit through Medicare — you would buy hearing aids privately or through a discount program like those offered by AARP or Costco.

How to choose between Medigap and Advantage based on your coverage needs

Start with what matters most to you. If you take multiple prescription drugs, you need either Advantage (which includes Part D) or Original Medicare plus Medigap plus Part D. If you want the lowest out-of-pocket costs for hospital and doctor visits, Medigap usually wins — you pay a higher premium but lower costs when you use care. If you want dental and vision included, Advantage is your only option within Medicare.

If you have a chronic condition and see the same doctors regularly, check whether they are in your Advantage plan's network before you enroll. If you travel frequently or live part of the year in another state, Medigap is simpler — it works with any doctor who accepts Medicare, anywhere in the country. Advantage networks are local.

If you are healthy, take few drugs, and rarely see a doctor, Advantage plans often cost less in premiums. If you use a lot of care or have expensive prescriptions, Medigap plus Part D often costs less overall, even with a higher premium. The math is personal — compare your actual drugs and doctors against actual plan costs, not against general rules.

Frequently Asked Questions

Can I have both Medigap and Medicare Advantage at the same time?

No. You choose one or the other. If you enroll in Advantage, your Medigap coverage ends. If you later switch back to Original Medicare, you can buy Medigap again, but you may lose may provide issue rights and pay higher premiums depending on your state and how long you were without coverage.

What happens if I do not sign up for Part D when I first become may be able to access?

You pay a permanent penalty added to your Part D premium every month for the rest of your life. The penalty is roughly 1 percent of the national average Part D premium per month you were without coverage. If you delay for two years, you pay that penalty forever, even if you later enroll.

Does Medicare Advantage cover out-of-network doctors in emergencies?

Yes. Emergency care is covered out-of-network. Urgent care (not an emergency, but you need care soon) may or may not be covered out-of-network depending on your plan. Check your plan documents or call the plan before you travel to know what is covered.

If my Advantage plan covers dental, does it cover all dental work?

No. Most Advantage dental benefits cover preventive care (cleanings, exams) at no cost, but limit or exclude major work like crowns, root canals, and extractions. Check your plan's dental summary or call the plan to see what is covered for the specific work you need.

Can I switch from Medigap to Advantage in the middle of the year?

Only during the annual enrollment period (October 15 to December 7) or if you have a may have access to life event like moving out of your plan's service area, losing employer coverage, or becoming newly may be able to access for Medicaid. Otherwise, you must wait until the next enrollment period.