Switching from Original Medicare to Medicare Advantage: A Step-by-Step Walkthrough
Key Takeaways
- You can switch from Original Medicare to Medicare Advantage only during specific enrollment windows each year.
- You must remain enrolled in Medicare Parts A and B to join any Medicare Advantage plan.
- Medicare Advantage plans vary significantly by network, cost-sharing, and extra benefits — comparison shopping is essential.
- Dropping a Medigap (supplement) policy to join Medicare Advantage is usually permanent; re-entry is not guaranteed.
- The Annual Enrollment Period (October 15–December 7) is the most flexible time to make this switch.
- Confirming your doctors and prescriptions are covered before enrolling can prevent costly surprises.
Why People Switch — and What You're Actually Changing
Original Medicare — Parts A and B — is the federal government's direct coverage program. It pays for hospital stays (Part A) and outpatient medical care (Part B), but it leaves notable gaps: there's no cap on out-of-pocket costs, no routine dental or vision coverage, and prescriptions require a separate Part D plan. Many people patch those gaps with a Medigap (supplemental) policy.
Medicare Advantage (Part C) takes a different approach. Instead of the government paying providers directly, you enroll in a private insurance plan that has contracted with Medicare to deliver your Part A and Part B benefits — often bundling in Part D drug coverage, dental, vision, hearing, and other extras. See our full explanation of how Part C bundled coverage works for a deeper look at the structure.
The appeal is real: many Medicare Advantage plans charge $0 in additional premiums (you still pay your Part B premium), and the extra benefits can be genuinely valuable. But the tradeoffs are real too — network restrictions, prior authorization requirements, and out-of-pocket maximums that can still reach several thousand dollars annually. Before committing, it's worth reading through the full tradeoffs of Medicare Advantage so you go in clear-eyed.
Switching is not like changing a cable subscription. Timing matters enormously, and some decisions — particularly around Medigap — can be difficult or impossible to reverse. This walkthrough will take you through the process step by step.
What You Need Before You Start
Before you can meaningfully compare plans or initiate an enrollment, gather the following. Having this information in hand will make every subsequent step faster and more accurate.
What you will need
Once you have these materials ready, you're positioned to evaluate plans with real precision rather than guessing whether your cardiologist is in-network or whether your insulin will be covered at a reasonable tier.
Medicare Plan Finder (Medicare.gov/plan-compare)
The official CMS tool for comparing Medicare Advantage and Part D plans available in your ZIP code, including drug cost estimates.
SHIP (State Health Insurance Assistance Program) Counselor
Free, unbiased one-on-one counseling from a certified specialist to help you evaluate plans without a sales agenda.
Your Plan's Evidence of Coverage (EOC) Document
The legal document detailing exactly what your Medicare Advantage plan covers, costs, and requires — essential for verifying benefits.
Prescription Drug List (Formulary) from Each Plan
Confirms whether your specific medications are covered, at which cost tier, and under what conditions.
Licensed Medicare Insurance Agent
Can help compare plans across multiple carriers and explain trade-offs, though they earn commissions so verify their recommendations independently.
When You Can Actually Make the Switch
Enrollment windows for Medicare are strictly governed by federal rules. You cannot switch from Original Medicare to Medicare Advantage at any time — you must act within one of these designated periods:
| Enrollment Period | Dates | Who It Applies To |
|---|---|---|
| Initial Enrollment Period (IEP) | 7-month window around your 65th birthday | People first becoming eligible for Medicare |
| Annual Enrollment Period (AEP) | October 15 – December 7 | Anyone on Medicare; changes take effect January 1 |
| Medicare Advantage Open Enrollment | January 1 – March 31 | People already enrolled in a Medicare Advantage plan (switch plans or return to Original Medicare) |
| Special Enrollment Period (SEP) | Varies by qualifying event | Moving, losing other coverage, qualifying for low-income subsidies, etc. |
For most people already on Original Medicare who are simply reconsidering their coverage, the Annual Enrollment Period (AEP) is the primary opportunity. You have nearly two months to research, compare, and enroll — and your new coverage begins January 1 of the following year.
Missing the Enrollment Window Has Consequences
If you miss the Annual Enrollment Period without a qualifying Special Enrollment Period, you must wait until the following AEP (October 15–December 7) to make changes. There is no grace period. Mark your calendar well in advance and start researching plans in September — before the window officially opens — so you're ready to enroll on October 15 if needed.
If you're new to Medicare and still in your Initial Enrollment Period, you have more flexibility. You can choose Medicare Advantage from the start rather than defaulting to Original Medicare first. For a broader perspective on how to combine the various parts, see how to evaluate which bundle of Medicare parts fits your situation.
Step-by-Step: Making the Switch
Follow these steps in order. Each one builds on the last, and skipping ahead — particularly around Medigap cancellation — can lead to coverage gaps or locked-out options.
Confirm Your Parts A and B Are Active
Medicare Advantage is a delivery mechanism for your Parts A and B benefits — you cannot enroll in Part C without both being active. Log in to Medicare.gov or call 1-800-MEDICARE to verify your enrollment status. If you deferred Part B because you had employer coverage, you'll need to enroll in Part B before you can join any Medicare Advantage plan.
Also confirm whether you're paying any Income-Related Monthly Adjustment Amount (IRMAA) surcharges on your Part B or Part D premium — these surcharges apply regardless of whether you're on Original Medicare or Medicare Advantage, and they affect your total cost calculation.
Build Your 'Must-Cover' List
Before you look at a single plan, write down:
- The full names and practice locations of every doctor, specialist, and hospital you use regularly
- Every prescription drug you take, including dosage and frequency
- Any planned procedures or ongoing treatments in the coming year
- Any benefits that matter to you beyond basic medical — dental, vision, hearing aids, fitness programs, transportation
This list becomes your evaluation filter. Any plan that doesn't cover your doctors or drugs at an acceptable cost tier is off the table, regardless of how attractive the premium looks.
Use the Medicare Plan Finder to Compare Options
Go to Medicare.gov/plan-compare and enter your ZIP code. You'll be prompted to enter your drugs (by name and dosage) and your preferred pharmacy. The tool will generate a list of available plans in your area with estimated annual costs — including premiums, drug costs, and expected medical cost-sharing based on your usage.
Sort by estimated annual cost, not just monthly premium. A $0-premium plan with high specialist copays and a narrow formulary can easily cost more over a year than a plan with a modest premium but lower cost-sharing.
For each plan you're seriously considering, click through to check:
- The provider directory (confirm your specific doctors are listed)
- The drug formulary (confirm your medications are covered at what tier)
- The out-of-pocket maximum (the cap on what you'll pay in a year)
- Prior authorization requirements for any services you use regularly
Evaluate the Plan's Star Rating
Medicare rates every Medicare Advantage plan on a 1–5 star scale based on quality of care, member satisfaction, and plan administration. You can see these ratings directly in the Medicare Plan Finder. A 4-star or higher rating is generally a positive signal, though ratings can change year to year.
High-star plans also earn additional federal bonuses that plans sometimes pass back to members as richer benefits. Conversely, plans that drop below 3 stars for multiple consecutive years can be terminated by CMS — which would force you to re-enroll in a new plan anyway.
Decide What to Do With Your Medigap Policy
If you currently have a Medigap policy, you need to make a deliberate decision here — do not let it cancel automatically or ignore it. Once you enroll in Medicare Advantage, your Medigap policy becomes largely useless (Medicare Advantage plans don't work with Medigap), but the insurer will still charge you premiums unless you actively cancel.
Contact your Medigap insurer directly to cancel your policy. Time the cancellation so it aligns with your Medicare Advantage effective date — typically January 1 if you're enrolling during the AEP. Do not cancel early and leave yourself with a gap.
Critically: understand that canceling your Medigap policy likely ends your guaranteed issue rights for that policy. Read the Medigap section in this article carefully before taking this step.
Enroll in Your Chosen Medicare Advantage Plan
You have three ways to enroll:
- Online: Through Medicare.gov/plan-compare — the most direct and documented method
- By phone: Call the plan directly or call 1-800-MEDICARE
- Through a licensed insurance agent or SHIP counselor: A State Health Insurance Assistance Program (SHIP) counselor provides free, unbiased help — find yours at shiphelp.org
When you enroll, you'll need your Medicare number (from your red-white-and-blue card) and your Part A and Part B effective dates. The plan will notify Medicare of your enrollment; you do not need to separately notify Medicare that you're switching from Original Medicare.
You will also need to enroll in a Part D drug plan if your chosen Medicare Advantage plan does not include prescription drug coverage (known as an MA-only or MAPD plan distinction). Most Medicare Advantage plans today include Part D, but confirm before assuming.
Cancel or Adjust Any Standalone Part D Plan
If you had a standalone Part D prescription drug plan while on Original Medicare, check whether your new Medicare Advantage plan includes drug coverage (most do — these are called MAPD plans). If it does, your standalone Part D plan must be cancelled — you cannot have both active simultaneously, and the coordination rules can create billing problems.
Your new Medicare Advantage plan enrollment typically triggers an automatic disenrollment from a standalone Part D plan, but confirm this with both plans to avoid duplicate premium billing. If your Medicare Advantage plan does not include drug coverage, you'll need to keep or find a standalone Part D plan.
The Medigap Problem: What Most People Miss
This deserves its own section because it catches people off guard more than anything else in this process.
If you currently have a Medigap policy alongside Original Medicare, you are not automatically protected if you later want to return to Original Medicare and reapply for Medigap coverage. Here's why that matters:
- When you first enrolled in Medigap during your guaranteed issue window, insurers could not deny you coverage or charge more due to health conditions.
- If you drop Medigap to join Medicare Advantage and later want Medigap again, you'll be applying outside that guaranteed window in most states.
- Most states allow insurers to use medical underwriting — meaning they can deny your application or charge significantly higher premiums based on your health history.
Medigap Cancellation Is Usually Permanent
If you drop a Medigap policy to enroll in Medicare Advantage and later decide to return to Original Medicare, you will almost certainly lose your guaranteed issue rights for Medigap in most states. Insurers can reject your application or charge significantly higher premiums based on your health history. This is one of the most consequential — and least reversible — aspects of switching to Medicare Advantage. Do not cancel your Medigap policy until you are fully committed to making this switch long-term.
A small number of states (Connecticut, Massachusetts, Maine, New York, and a few others) have year-round guaranteed issue protections for Medigap, but they are the exception. Check your state's rules before making any decisions.
The practical implication: if you're considering switching to Medicare Advantage primarily for cost reasons and you're in good health now, think carefully about what happens if your health changes. Being locked out of Medigap later could cost far more than you save today. The comparison in Original Medicare vs. Medicare Advantage lays out this long-term cost picture clearly.
After Enrollment: Confirming Your Coverage Is Active
Enrollment is not the finish line — confirming that everything is set up correctly is just as important. A few critical steps to take after you've submitted your enrollment:
- Watch for your plan member ID card. It should arrive within 2–4 weeks of enrollment. Your Medicare Advantage plan card replaces your red-white-and-blue Medicare card for most services — though you should keep the original card in a safe place.
- Verify enrollment on Medicare.gov. Log in to your account at Medicare.gov and confirm your plan shows as active under the correct effective date.
- Call your primary care doctor's office. Confirm they have you listed under your new plan and that your insurance information is updated in their system before your next appointment.
- Review your Evidence of Coverage (EOC) document. Your plan is required to mail this to you by October 15 each year. It is the definitive, legal description of what your plan covers, what it costs, and what the rules are. Read the drug formulary section carefully.
- Set up your plan's online portal. Most Medicare Advantage plans have member portals where you can find in-network providers, check prior authorization requirements, and manage claims.
Use a SHIP Counselor at No Cost
Every state has a State Health Insurance Assistance Program (SHIP) that provides free, one-on-one counseling to Medicare beneficiaries. SHIP counselors don't sell insurance — they help you understand your options objectively. If you're feeling overwhelmed by plan comparisons or the Medigap decision, scheduling a free SHIP appointment before the AEP opens is one of the best uses of your time. Find your local SHIP at shiphelp.org.
Review Your Plan Every Year During AEP
Medicare Advantage plans can change their premiums, formularies, provider networks, and benefits from year to year. What was the best plan for you in 2024 may not be the best in 2025. Make it a habit to review your Annual Notice of Change (ANOC) document — mailed each September — and compare your current plan against alternatives every October before the AEP closes.
If you realize you made a mistake — chose the wrong plan, or enrolled in Medicare Advantage when you wanted to stay on Original Medicare — the Medicare Advantage Open Enrollment Period (January 1–March 31) gives you one opportunity to switch to a different Medicare Advantage plan or return to Original Medicare. You cannot use this period to add Medigap with guaranteed issue rights, however. For a comprehensive pre-enrollment checklist to help you avoid regrets, see questions to ask before enrolling in any Medicare part.
All claims in this article are backed by peer-reviewed research. We follow strict editorial guidelines to ensure accuracy and reliability. Sources available on request from our editorial team.
