Medicare is the federal health insurance program that covers Americans 65 and older, along with certain younger people with disabilities. It pays for hospital stays, doctor visits, preventive screenings, prescription drugs, and more. The program is split into distinct parts, each handling a different slice of healthcare costs.
Who Qualifies for Medicare
You’re automatically enrolled in Medicare when you turn 65. If you’re already receiving Social Security benefits at that point, your coverage starts without any action on your part. You’ll receive both Part A (hospital insurance) and Part B (medical insurance).
You don’t have to wait until 65 if you have a qualifying disability. After receiving Social Security disability benefits for 24 months, Medicare kicks in automatically. One exception: people diagnosed with ALS (Lou Gehrig’s disease) get Medicare as soon as their disability benefits begin, with no waiting period.
Your first chance to sign up is called the Initial Enrollment Period, a 7-month window that starts 3 months before you turn 65 and ends 3 months after. Missing this window matters. You may face a late enrollment penalty that increases the longer you wait and stays attached to your monthly premium for as long as you have coverage.
Part A: Hospital and Inpatient Care
Part A covers the big-ticket medical events: inpatient hospital stays, skilled nursing facility care, hospice care, and some home health services. Most people pay no monthly premium for Part A because they or a spouse paid Medicare taxes during their working years.
For skilled nursing facility care, Medicare covers up to 100 days per benefit period, but only after a qualifying hospital stay of at least 3 consecutive inpatient days. The first 20 days are fully covered after you meet the deductible ($1,736 in 2026). Days 21 through 100 come with a daily copay of $217 in 2026. After day 100, you’re responsible for the full cost. A benefit period resets once you’ve gone 60 consecutive days without inpatient hospital or skilled nursing care.
Part B: Doctor Visits and Preventive Care
Part B handles the outpatient side of medicine: doctor appointments, lab tests, outpatient surgeries, durable medical equipment like wheelchairs and hospital beds, and home health care. The standard monthly premium for Part B is $185.00 in 2025, with an annual deductible of $257. After you meet the deductible, you typically pay 20% of the cost for most services.
Preventive care is where Part B stands out. You pay nothing for most preventive services when you see a provider who accepts Medicare. The list is extensive:
- Cancer screenings: mammograms, colonoscopies, lung cancer screenings, cervical and prostate cancer screenings
- Cardiovascular disease screenings and behavioral therapy
- Diabetes screenings, self-management training, and the Medicare Diabetes Prevention Program
- Depression and alcohol misuse screenings
- HIV screenings and PrEP for HIV prevention
- Hepatitis B and C screenings
- Glaucoma tests and bone density measurements
- Vaccines: flu, COVID-19, pneumococcal, and hepatitis B shots
- A one-time “Welcome to Medicare” preventive visit and a yearly wellness visit
Tobacco cessation counseling, obesity behavioral therapy, and medical nutrition therapy are also covered at no cost to you.
Part D: Prescription Drug Coverage
Part D helps pay for prescription medications, including many recommended vaccines. It’s offered through private insurance companies approved by Medicare, and each plan maintains its own formulary, a list of drugs it covers. Plans are required to include at least two drugs in the most commonly prescribed categories, but beyond that, coverage varies.
Most plans organize drugs into tiers that determine what you pay. Generic drugs sit in the lowest tier with the smallest copay. Preferred brand-name drugs cost more, non-preferred brands cost more still, and specialty medications carry the highest copay. Before choosing a plan, it’s worth checking whether your specific medications appear on that plan’s formulary and which tier they fall into. The difference between tiers can mean paying $10 versus $100 for the same prescription.
Medicare Advantage (Part C)
Medicare Advantage is an alternative way to receive your Medicare benefits. Instead of getting Part A and Part B directly from the federal government, you enroll in a plan run by a private insurance company. These plans must cover everything Original Medicare covers, and most also bundle in Part D drug coverage.
The key tradeoffs between Original Medicare and Medicare Advantage come down to flexibility versus extra protections. With Original Medicare, you can see any doctor or hospital in the country that accepts Medicare. Medicare Advantage plans typically require you to use an in-network provider for non-emergency care, or pay higher costs for going out of network.
In exchange for that network restriction, Medicare Advantage plans cap your yearly out-of-pocket spending. Once you hit that limit, you pay nothing for covered services the rest of the year. Original Medicare has no such cap on its own. Many Medicare Advantage plans also offer benefits that Original Medicare doesn’t touch, like routine dental, vision, hearing, and fitness programs.
What Medicare Does Not Cover
Original Medicare has some notable gaps. It does not cover:
- Most dental care, including cleanings, fillings, extractions, and dentures
- Eye exams for prescription glasses
- Hearing aids and fitting exams
- Long-term custodial care (help with daily activities like bathing or dressing)
- Cosmetic surgery
- Massage therapy
- Routine physical exams (though the annual wellness visit is covered)
These exclusions are one of the main reasons people either choose Medicare Advantage plans, which often add dental and vision benefits, or purchase supplemental coverage.
Filling the Gaps With Medigap
If you stick with Original Medicare, a Medigap policy (also called Medicare Supplement Insurance) can help cover costs that Parts A and B leave behind. These policies are sold by private insurers and specifically target the out-of-pocket expenses built into Original Medicare: copayments, coinsurance (the 20% you owe after the Part B deductible), and deductibles.
Medigap only works alongside Original Medicare. If you’re enrolled in a Medicare Advantage plan, you can’t use a Medigap policy. The choice between these two paths is one of the biggest decisions new Medicare enrollees face: Original Medicare plus Medigap gives you nationwide provider access with predictable costs, while Medicare Advantage bundles more benefits into one plan but limits your network.