Medicare Advantage Plans: The Complete Guide

What is Medicare Advantage (Part C)?

Medicare Advantage, established under Title XVIII Part C of the Social Security Act, is a private health insurance alternative to Original Medicare. Approved and regulated by the federal government, these plans are offered by private insurance companies that contract with the Centers for Medicare & Medicaid Services (CMS). When you enroll in a Medicare Advantage plan, the government pays the private plan a fixed monthly amount to manage your healthcare services.

By federal law, Medicare Advantage plans must cover all services that Original Medicare Part A and Part B cover (such as emergency room visits, hospitalizations, surgeries, and doctor appointments). However, the way you access these services is different. Rather than billing the federal government, your providers bill your private insurance plan directly, subject to the plan's copayments, network rules, and prior authorization requirements.

Over 50% of eligible Medicare beneficiaries are enrolled in Medicare Advantage plans. Their popularity stems from their lower upfront monthly premiums, combined with the convenience of bundling medical and drug coverage into a single card. To see how Part C stacks up against traditional coverage, explore our flagship Medicare Plan Comparison Hub.

Types of Medicare Advantage Plans Available

Medicare Advantage plans are managed care networks. The specific rules for getting care depend on the plan design you choose:

1. Health Maintenance Organizations (HMOs)

HMO plans are the most common and restrictive plan design. You must receive all non-emergency care from healthcare providers within the plan’s local network. You are required to designate a Primary Care Physician (PCP) who coordinates your care, and you must obtain a formal referral from your PCP before seeing any specialists. Out-of-network services are not covered, meaning you are responsible for 100% of the cost if you see an unauthorized provider.

2. Preferred Provider Organizations (PPOs)

PPO plans offer greater provider flexibility. You can see any doctor or visit any hospital that accepts Medicare, but you pay significantly lower out-of-pocket costs if you use network providers. You are not required to select a PCP, and you do not need referrals to see specialists. PPO plans are popular with retirees who travel or split their time between different states.

3. Special Needs Plans (SNPs)

SNPs are specialized plans tailored to individuals with specific health or financial circumstances. The most common type is the Dual-Eligible Special Needs Plan (D-SNP), designed for individuals who qualify for both Medicare and Medicaid. Other SNPs serve individuals living in nursing homes (I-SNPs) or those with chronic conditions like diabetes, heart failure, or dementia (C-SNPs). These plans coordinate drug formularies and provider networks specifically around the group's medical needs.

Understanding Medicare Advantage Costs & the $9,250 MOOP

While many Medicare Advantage plans feature a $0 monthly premium (in addition to your standard $202.90 Part B premium), your financial exposure shifts to copayments and coinsurance when you access care. In 2026, CMS establishes strict Maximum Out-of-Pocket (MOOP) limits:

• In-Network MOOP: The federal maximum is $9,250 per calendar year. Once you pay $9,250 in covered in-network copays and coinsurance, the plan pays 100% of covered clinical services for the rest of the year.
• Combined In- and Out-of-Network MOOP (PPO Plans): The federal maximum is $13,900 for 2026.

To evaluate catastrophic risk and compare how Medigap Plan G eliminates these copayments, test your scenarios with our Worst-Case Exposure Calculator and our Medicare Advantage vs. Original Medicare Cost Checker.

Special Enrollment Rules: The Medicare Advantage OEP

If you are enrolled in a Medicare Advantage plan, you have access to a unique enrollment window that is not available to Original Medicare beneficiaries. The Medicare Advantage Open Enrollment Period (MA OEP) runs annually from January 1 to March 31.

According to official Medicare.gov enrollment rules, you can make exactly one change during this window:

• Switch from one Medicare Advantage plan to another Medicare Advantage plan.
• Drop your Medicare Advantage plan and return to Original Medicare. If you make this transition, you are permitted to enroll in a stand-alone Part D prescription drug plan to maintain creditable drug coverage.

For a complete timeline of all signup periods, consult our comprehensive Medicare Enrollment Hub and our Turning 65 Decision Guide.