Medicare basics: Original Medicare vs Medicare Advantage, Medigap and Part D
You choose between two main paths. Original Medicare (Part A hospital + Part B medical) lets you see any provider that takes Medicare nationwide; you can add a Part D drug plan and a Medigap policy to cover your share of costs. Medicare Advantage (Part C) is an all-in-one plan from a private company approved by Medicare that usually includes drug coverage and extras, but often limits you to a network. Medigap only works with Original Medicare, and your best chance to buy it is in the 6 months after you first have Part B at 65+.
The parts of Medicare
- Part A (Hospital Insurance): inpatient hospital stays, skilled nursing facility care, hospice and some home health care. Most people don't pay a Part A premium.
- Part B (Medical Insurance): doctor services, outpatient care, preventive services and medical equipment. Most people pay a monthly Part B premium.
- Part C (Medicare Advantage): private plans approved by Medicare that replace Original Medicare for how you get your Part A and B benefits.
- Part D (drug coverage): prescription drug plans from private companies, either stand-alone or included in most Medicare Advantage plans.
Original Medicare vs Medicare Advantage
| Original Medicare | Medicare Advantage | |
|---|---|---|
| Doctors and hospitals | Any provider that accepts Medicare, anywhere in the U.S. | In many cases, only providers in the plan's network |
| Drug coverage | Add a separate Part D plan | Most plans include Part D |
| Help with your share of costs | Add Medigap, retiree coverage or Medicaid | Built into the plan's cost-sharing; Medigap can't be used |
| Extra benefits | Generally no routine dental, vision or hearing | Most plans offer extras like vision, hearing and dental |
| Yearly out-of-pocket limit | None, unless you have supplemental coverage | Yes, each plan has an annual limit on covered Part A and B costs |
| Referrals and prior authorization | Generally not required | Often required, depending on the plan |
Summarized from Medicare.gov, Your coverage options.
Medigap (Medicare Supplement Insurance)
- Sold by private companies to help pay your share of costs in Original Medicare (deductibles, coinsurance).
- Policies are standardized and, in most states, named by letters such as Plan G or Plan N. The benefits in each lettered plan are the same no matter which company sells it; price is the only difference.
- Generally doesn't cover long-term care, vision, dental, hearing aids or prescription drugs.
- Your Medigap Open Enrollment Period is a one-time, 6-month window starting the first month you're 65 or older and have Part B. During it, insurers generally can't deny you or charge more for health problems. After it, you may be turned down or pay more in many states.
Part D drug coverage
Each Part D plan has its own list of covered drugs (formulary), organized into cost tiers. If you go 63 days or more without Part D or other creditable drug coverage after you first become eligible, you may pay a late enrollment penalty for as long as you have Part D. Compare plans using your actual prescriptions on Medicare.gov's Plan Finder.
How to decide
- If keeping any doctor nationwide and predictable costs matter most, compare Original Medicare + Medigap + Part D.
- If a lower monthly cost and bundled extras matter more and your doctors are in network, compare Medicare Advantage plans.
- Check every plan against your doctors, prescriptions and pharmacies.
- Free, unbiased counseling is available from your State Health Insurance Assistance Program (SHIP), which isn't connected to any insurer.
Timing matters as much as the choice. See Medicare enrollment periods.
Frequently asked questions
What's the difference between Medicare Advantage and Medigap?
Medicare Advantage replaces Original Medicare with a private plan that bundles your benefits. Medigap is a supplement that works only with Original Medicare to help pay your share of costs. You can't use Medigap with a Medicare Advantage plan.
Does Original Medicare have an out-of-pocket maximum?
No. Original Medicare has no yearly limit on what you pay, which is why many people add Medigap or other supplemental coverage. Medicare Advantage plans have an annual out-of-pocket limit.
When is the best time to buy Medigap?
During your 6-month Medigap Open Enrollment Period, which starts the first month you're 65 or older and enrolled in Part B. Insurers generally can't deny you or charge more for health conditions during that window.
Are Medigap Plan G policies the same from every company?
Yes. Medigap plans with the same letter have the same benefits regardless of insurer; price is the only difference. Massachusetts, Minnesota and Wisconsin standardize differently.
Where can I get free unbiased Medicare help?
Your State Health Insurance Assistance Program (SHIP) offers free one-on-one counseling, and you can call 1-800-MEDICARE or compare plans at Medicare.gov.
Sources
- Medicare.gov: Your coverage options (accessed October 28, 2026)
- Medicare.gov: When can I buy a Medigap policy? (accessed October 28, 2026)
- Medicare.gov: Joining a plan (enrollment periods) (accessed October 28, 2026)
- Medicare.gov: Plan Finder (compare Medicare plans) (accessed October 28, 2026)
- SHIP National Technical Assistance Center: find your State Health Insurance Assistance Program (accessed October 28, 2026)