What is covered under part B of Medicare?

The single biggest and most costly mistake people make with Medicare is missing enrollment deadlines, leading to permanent late-enrollment penalties and gaps in coverage.

Missing Enrollment Deadlines

• Initial Enrollment Period (IEP): This window lasts for seven months. It starts three months before the month you turn 65, includes your birthday month, and ends three months after.
• Late Penalties: Failing to sign up for Part B or Part D on time can trigger permanent monthly or yearly financial penalties added to your premiums.
• Delayed Enrollment Confusion: Many people wrongly assume they can delay Medicare past age 65 just because they have health coverage like COBRA, a marketplace plan, or small-employer insurance.

Other Costly Medicare Mistakes

• Ignoring Annual Changes: Sticking with automatic renewal without reading the Annual Notice of Change (ANOC) can result in unexpected costs, as drug lists and doctor networks shift every year.
• Choosing Solely by Low Premiums: Picking a plan based only on a low monthly cost while ignoring total out-of-pocket expenses like deductibles, copays, and coinsurance.
• Missing the Medigap Window: Forgetting to apply for a Medigap (Medicare Supplement) policy during your open enrollment window. After this six-month period, insurers can use medical underwriting to charge more or deny coverage.
• Skipping Financial Assistance: Overlooking programs like Medicare Savings Programs or Part D Extra Help that assist with out-of-pocket medical and prescription expenses.

People opt out or delay enrollment in Medicare Part B primarily to avoid monthly premium costs when they already have active, qualifying health insurance from an employer.

Main Reasons for Opting Out

• Active Employer Coverage: Individuals (or their spouses) who continue working past age 65 often keep their employer-sponsored health plan if the company has 20 or more employees. If this coverage is considered "creditable," they can delay Part B without facing late penalties.
• High Premium Costs and IRMAA: High-income earners pay an Income-Related Monthly Adjustment Amount (IRMAA), which significantly increases their standard Part B monthly premium. Some retirees opt out or evaluate alternative private plans if the extra cost outweighs the perceived value.
• Alternative Government Plans: Some federal retirees with robust coverage through programs like the Federal Employees Health Benefits (FEHB) program choose to delay Part B to preserve their immediate cash flow.

Risks of Opting Out

• Permanent Late Penalties: Dropping or delaying Part B without valid, active employer coverage results in a permanent 10% late enrollment penalty for every 12 months you go without coverage.
• Loss of Supplemental Options: Without Part B, you cannot enroll in Medigap (Medicare Supplement) or standard Medicare Advantage plans.

Critics and beneficiaries advise caution with Medicare Advantage plans because of restrictions on care, unexpected costs, and administrative hurdles. While these private plans often feature low or zero monthly premiums and extra perks like dental or vision, they come with significant trade-offs.

Restricted Provider Networks

• Local limitations: Most plans use specific HMO or PPO networks, meaning you must see doctors and go to hospitals within the plan’s local area.
• No nationwide freedom: Unlike Original Medicare, which lets you see any accepting doctor nationwide, Medicare Advantage offers very limited coverage when traveling.
• Frequent changes: Provider lists can change annually or even during the year, meaning your favorite doctor might leave the network unexpectedly.

Prior Authorization and Denials

• Approval delays: Private insurers often require "prior authorization" (advance permission) for specialized care, MRIs, surgeries, or rehabilitation.
• Care obstacles: This review process can delay or block medically necessary treatments.

High Out-of-Pocket Costs

• Cost-sharing for serious illnesses: While plans have annual out-of-pocket maximums (up to thousands of dollars), treatments like chemotherapy or expensive infusions can trigger steep 20% coinsurance charges before you reach that cap.
• End-of-life complications: High utilization during severe or chronic illness can result in major expenses or coverage friction.

The "Medigap" Trap

• Locked-in coverage: If you try to switch back to Original Medicare after a 12-month trial period, moving to a Medicare Supplement (Medigap) plan often requires passing medical underwriting. Pre-existing health conditions can make it difficult or impossible to qualify for a good supplement later.

A Medicare Advantage plan (Part C) offered by private insurance companies is the only type of private insurance that can bundle and replace your Original Medicare Part A and Part B benefits.

How Medicare Advantage Replaces Part B

• Alternative delivery: These plans are approved by Medicare and provided by private insurers (like Humana Medicare Advantage plans or local Blue Cross and Blue Shield options).
• Required enrollment: You must still be enrolled in Original Medicare (and typically continue paying your Part B premium) to join a Medicare Advantage plan, but your actual medical care and doctor visits are managed and paid for by the private plan.
• Extra perks: These plans often include prescription drug coverage (Part D) and extra benefits like dental, vision, or hearing that standard Part B does not cover.

Important Clarifications

• Medigap is different: A Medicare Supplement (Medigap) policy does not replace Part B. Medigap works alongside Original Medicare to pay for out-of-pocket costs like coinsurance and copays.
• ACA Marketplace: You cannot use a regular Affordable Care Act (Obamacare) marketplace plan to replace Medicare Part B.

Medicare Part A is free (has a $0 monthly premium) for most seniors aged 65 and older.

Who Gets Free Part A?

You do not pay a monthly premium for Part A if you or your spouse worked and paid Medicare taxes for at least 10 years (40 work quarters). About 99% of people qualify for this premium-free coverage.

Who Has to Pay for Part A?

If you do not have enough work credits, you can still buy Part A, but you will pay a monthly fee:

• 30 to 39 work quarters: $311 per month
• Fewer than 30 work quarters: $565 per month

Other Part A Costs

Even with a $0 monthly premium, Part A is not completely free when you use care. You still have out-of-pocket costs:

• Hospital deductible: $1,736 per benefit period (in 2026)
• Daily coinsurance: $0 for the first 60 days, but it increases for longer hospital stays or skilled nursing care.

You can review official details through the Fact Sheet on 2026 Medicare Costs.