1. The four parts, in one screen
Hospital insurance
Inpatient hospital stays, skilled nursing facility care, hospice, some home health care. Most people pay no premium for Part A because they or a spouse paid Medicare taxes while working.
Medical insurance
Doctor visits, outpatient care, preventive services, durable medical equipment. Part B has a monthly premium that is set by the federal government each year, and higher earners pay more.
Medicare Advantage
A private plan that takes over your Part A and Part B coverage, usually with a network of doctors. Many of these plans include prescription drug coverage and extras.
Prescription drug coverage
Prescription coverage, offered through private plans. Each plan covers a specific list of drugs, so the right plan depends on the prescriptions you actually take.
Current premiums, deductibles and income-related amounts change every year. Check them at Medicare.gov costs.
2. Two paths — this is the real decision
Almost every Medicare decision comes down to which of these two structures you want. Neither one is universally better.
Path 1 — Original Medicare (plus optional add-ons)
- You use Part A and Part B directly, and you can see any provider in the country that accepts Medicare.
- There is no annual out-of-pocket limit on its own, which is why many people add a Medicare Supplement (Medigap) policy.
- Prescription coverage is separate — you add a standalone Part D plan.
Path 2 — Medicare Advantage (Part C)
- A private plan replaces how your Part A and Part B benefits are delivered, usually through a network.
- Plans have an annual out-of-pocket maximum, and many include drug coverage plus extra benefits.
- You generally need to stay in-network, and referrals or prior authorization may apply.
Compare the structures yourself at Medicare.gov coverage options.
3. Timing — the part that costs people money
3 months before through 3 months after your 65th birthday month
Your Initial Enrollment Period — a seven-month window around turning 65. This is the cleanest time to enroll.
October 15 – December 7 every year
Medicare Open Enrollment (also called the Annual Election Period). You can change Advantage and Part D plans for the following year.
January 1 – March 31 every year
Medicare Advantage Open Enrollment. If you're already in an Advantage plan, you get one change during this window.
The 60 days starting on your birthday (California only)
California's 'birthday rule' lets people with a Medicare Supplement policy switch to another one with equal or lesser benefits without new medical underwriting. Most states have nothing like it.
Enrollment window details: Medicare.gov sign-up. California Medigap rules: California Department of Insurance.
4. Four mistakes we see over and over
Assuming you'll be enrolled automatically
Some people are enrolled automatically; many are not. If you're not already receiving Social Security benefits, you generally have to sign up yourself.
Delaying Part B or Part D without qualifying coverage
Late enrollment penalties are added to your premium and, in most cases, they last for as long as you have that coverage. Employer coverage may let you delay — but the rules depend on the employer's size.
Choosing a plan before checking your own doctors and drugs
Networks and drug lists change every year. A plan that's perfect for your neighbor can be the wrong plan for you for reasons that have nothing to do with price.
Ignoring dental, vision and hearing
Original Medicare generally doesn't cover routine dental, vision or hearing care. That surprises people at exactly the wrong moment.
Still confused about one specific thing?
That's normal — this system was not designed to be understood. Send us the question and you'll get a written answer from a person.
Ask your questionYou can also get free, unbiased counseling from California's HICAP program at aging.ca.gov/HICAP.