Short answer
Lettered plans supplement Original Medicare; Part C is Medicare Advantage.
Medicare.gov says Medigap plans are named by letters, like Plan C or Plan G, and supplement Original Medicare. Medicare Advantage is Part C, an alternative way to get your Medicare through a private plan. Medicare.gov says you can either buy a Medigap policy or join a Medicare Advantage Plan, but not both. So a lettered plan and Part C are different choices, not two names for the same thing.
Start here
What you actually came to find out
Plain answers first. Sources stay below for checking details.
Is Plan C the same as Part C?
No. Plan C is a Medigap letter; Part C is Medicare Advantage.
Which goes with Original Medicare?
Medigap lettered plans supplement Original Medicare.
Can I have both?
No. Medicare.gov says you pick Medigap or Medicare Advantage, not both.
Does the brand tell me which I have?
No. The same company can sell both, so check the plan type.
Medigap
Lettered plans
Medicare.gov says Medigap plans are named by letters and supplement Original Medicare.
Source trail: Medicare.gov
Medicare Advantage
Part C
Medicare.gov says Part C is an alternative way to get Medicare through a private plan.
Source trail: Medicare.gov
Either, not both
One path
Medicare.gov says you can buy Medigap or join Medicare Advantage, but not both.
Source trail: Medicare.gov
Brand vs type
Check the type
A single company can sell both, so the brand alone does not tell you which you have.
Source trail: Medicare.gov
The real planning question is whether you want Original Medicare with a supplement, or a Medicare Advantage plan that bundles coverage inside a network.
Neutral landscape
The shape of the question
Medicare.gov is the main source because it defines the parts of Medicare and names Medigap lettered plans separately from Part C.
Source trail: Medicare.gov
The boundary matters, so Medicare.gov states that Medigap is different from a Medicare Advantage Plan and that you cannot have both.
Source trail: Medicare.gov
The brand confusion is the practical trap because a company can sell both kinds, which is why plan type, not name, is the tell.
Source trail: Medicare.gov
The choice underneath is coverage structure, which Medicare.gov frames as Original Medicare plus a supplement versus a bundled private plan.
Source trail: Medicare.gov
Curator core
What the authorities say
These sources are here for the reader who wants to check the work. The plain-English answer stays above them.
Source 01
Medicare.gov
Parts of Medicare
Medicare.gov explains the parts of Medicare, including Original Medicare, Medigap lettered plans, and Medicare Advantage as Part C.
Source framing
Medicare.gov says Medigap plans are named by letters and supplement Original Medicare, while Medicare Advantage is Part C, an alternative way to get Medicare.
Strongest for: the difference between Medigap plan letters and Medicare Advantage
Read at Medicare.govSource 02
Medicare.gov
How Medigap Works
Medicare.gov explains that Medigap supplements Original Medicare, that policies sold after 2005 do not include drug coverage, and how Medigap pays after Medicare.
Source framing
Medicare.gov says a Medigap policy is a supplement to Original Medicare, that Medigap sold after 2005 does not include drug coverage, and that Medigap is different from a Medicare Advantage Plan.
Strongest for: how Medigap supplements Original Medicare and pairs with Part D
Read at Medicare.govPlain-English forks
The forks people face
Most retirement questions hide a few smaller decisions. These are the practical pieces that change the plan.
Original Medicare plus Medigap, or Medicare Advantage?
Why it matters: This is the real fork hiding behind plan letters and Part C.
In real life: This fork changes networks, premiums, and out-of-pocket risk.
What to look at: What to look at: Medicare.gov parts-of-Medicare and plan comparison.
What does your plan type actually say?
Why it matters: The brand can be either, so the plan type is the reliable label.
In real life: This fork tells you which structure you are really in.
What to look at: What to look at: your plan documents or member card details.
Do you want a supplement or a network?
Why it matters: Medigap pairs with Original Medicare; Advantage uses a plan network.
In real life: This fork shapes how you get care.
What to look at: What to look at: provider access and referral rules.
Common questions
Quick answers
Short, plain answers for the questions people usually have next. The source trail stays available below.
Is a Medigap Plan C the same as Medicare Part C?+
No. Medicare.gov says Plan C is a Medigap letter that supplements Original Medicare, while Part C is Medicare Advantage, an alternative way to get Medicare.
Is an AARP or UnitedHealthcare plan Original Medicare or Advantage?+
It can be either. Medicare.gov says a company can sell both Medigap and Medicare Advantage, so check the plan type rather than the brand.
Can I have both Medigap and Medicare Advantage?+
No. Medicare.gov says you can buy a Medigap policy or join a Medicare Advantage Plan, but not both.
Which one works with Original Medicare?+
Medicare.gov says Medigap lettered plans supplement Original Medicare; Medicare Advantage replaces how you get it.
How do I tell which I have?+
Check whether your plan is described as a Medigap supplement or a Medicare Advantage (Part C) plan in your plan documents.
How this page is curated
This page uses Medicare.gov parts-of-Medicare and how-Medigap-works. It separates plan letters from Part C because Medicare.gov treats them as different coverage structures.
Read the planner methodologyTrust anchor
Sources used on this page
Every source named above is listed here in one place.
Medicare.gov. Parts of Medicare
https://www.medicare.gov/basics/get-started-with-medicare/medicare-basics/parts-of-medicareMedicare.gov. How Medigap Works
https://www.medicare.gov/health-drug-plans/medigap/basics/how-medigap-works
Before you act on this
This plan is educational. It is not personalized financial, tax, or insurance advice. Projections illustrate the math, they do not predict the future. Talk to your own licensed financial professional before acting on any of it.