2.1 What Medicare Is: Program Structure & How Parts A–D Fit Together

Why This Section Matters

Module 1 (Medicare Basics) is 20% of the AHIP final, but its real weight is much higher than 20% — every question in Modules 2 through 5 assumes you already know which "Part" a benefit, cost, or rule belongs to. If you cannot instantly sort a scenario into Part A, B, C, or D, you will burn time flipping through your open-book notes on questions that should take ten seconds. Get this section fully internalized before moving forward.

What Medicare Is

Medicare is the federal health insurance program for people age 65 and older, and for certain younger people with disabilities or specific diagnoses. It was created in 1965 as Title XVIII of the Social Security Act and is administered by the Centers for Medicare & Medicaid Services (CMS), an agency within the U.S. Department of Health and Human Services (HHS). Unlike Medicaid, Medicare is not means-tested — eligibility is based on age, disability status, or specific medical diagnoses, not income.

Medicare has four parts, and the exam expects you to know both what each part covers and, just as importantly, who actually delivers it — the government directly, or a private insurance company under contract with CMS.

The Two Delivery Models

Every Medicare benefit reaches a beneficiary through one of two structural paths:

1. Original Medicare — Parts A and B together. CMS pays providers directly on a fee-for-service basis. There are no provider networks (any provider who accepts Medicare can be seen), no referrals required, and no annual cap on out-of-pocket spending unless the beneficiary layers on a Medigap policy.
2. Medicare Advantage (Part C) — A private insurance company contracts with CMS to deliver all Part A and Part B benefits (plus usually Part D) through its own plan design, often with networks, prior authorization, and referral requirements — but always with an annual out-of-pocket maximum (MOOP), which Original Medicare alone does not have.

This is the single most tested structural fact on the exam: Part C is not a fourth kind of coverage sitting next to A, B, and D — it is an alternative way of receiving A and B (and usually D). A beneficiary is never enrolled in "Part A, B, and C" simultaneously in the way they might have "Part A and Part B"; once someone elects an MA plan, that plan becomes their vehicle for the Part A/B benefit, replacing (not supplementing) Original Medicare for as long as they're enrolled.

The Four Parts at a Glance

A simple memory hook many agents use: Admission (hospital), Both-in-and-out-of-the-hospital doctor bills, Choice (the private alternative), Drugs.

Where Medigap Fits — and Where It Doesn't

Medigap (Medicare Supplement insurance) is regulated separately from the four Medicare parts and is sold by private insurers to fill Original Medicare's cost-sharing gaps — the Part A deductible, Part B coinsurance, and similar out-of-pocket amounts. The single fact the exam tests most on this topic: Medigap only works alongside Original Medicare. A beneficiary enrolled in a Medicare Advantage plan cannot also carry (or newly purchase) a Medigap policy to supplement that MA plan — the two products are not compatible, and it is illegal for an agent to sell a Medigap policy to someone the agent knows is enrolled in MA (with narrow exceptions such as a Medigap policy that predates MA-only trial-right situations covered later in Chapter 4).

A Working Scenario

A client tells you, "I have Medicare Part A and Part B, and I just enrolled in a Humana Medicare Advantage plan." What should you know instantly?

• The client is no longer using Original Medicare's fee-for-service structure for daily care — the Humana MA plan is now the delivery vehicle for their A and B benefits.
• The client's red-white-and-blue Original Medicare card still exists and still proves entitlement, but claims for routine care run through Humana's plan, not through CMS directly.
• If the client also has a Medigap policy from before they joined the MA plan, that Medigap policy provides no benefit while they're in the MA plan (some states allow “suspend” rights for certain circumstances, but the policy does not pay MA cost-sharing).

Common Traps

• Treating “Part C” as if it adds a distinct new benefit category, rather than recognizing it as a delivery alternative for A/B.
• Assuming Part D is automatically included with every MA plan — some MA plans (notably MSA and some PFFS plans) do not include drug coverage, and the beneficiary may need a stand-alone PDP or go without.
• Forgetting that hospice care always remains billed under Original Medicare Part A, even for a beneficiary enrolled in an MA plan — this is the one Part A/B benefit MA plans do not have to deliver directly (covered in more depth in Chapter 6).