What is this window

The Medicare Annual Enrollment Period is the once-a-year window when people who already have Medicare can make many Medicare Advantage and Part D changes for the next calendar year. For 2027 coverage, that window is in fall 2026. The plan generally must receive the request by December 7, 2026, for a change that starts January 1, 2027. Confirm the rule that fits you on Medicare.gov.

Why review even if you want to stay

Medicare Advantage and Part D plans can change every year. Premiums, copays, deductibles, drug lists, pharmacy networks, doctor networks, extra benefits, and prior approval rules in 2027 may not match 2026. If you already have one of those plans, read the Annual Notice of Change before you decide to keep it. Why the notice matters.

Dates for 2027 coverage

December 7, 2026 is the deadline that matters most. In most cases it is the last day to join, switch, or drop Medicare Advantage or stand-alone Part D coverage for the 2027 calendar year during Annual Enrollment.

  • October 1, 2026: a preparation date, now past. Plan notices were available then. Enrollment opened October 15 and runs through December 7.
  • October 15, 2026: Annual Enrollment begins (October 15 – December 7). This is when many 2027 plan changes can be submitted.
  • December 7, 2026: Annual Enrollment ends. The plan should have the request by this date for a January 1 start.
  • January 1, 2027: new coverage begins, or your current plan renews with its 2027 changes if you stayed.
  • January 1 through March 31, 2027: the Medicare Advantage Open Enrollment Period (January 1 – March 31). It applies only if you are already in a Medicare Advantage plan, and it allows one limited change. It is not a second full Annual Enrollment.

When people say “open enrollment”

That phrase is used for two different windows. Use Annual Enrollment for the fall window. For 2027 coverage, Annual Enrollment is October 15 through December 7, 2026. The Medicare Advantage Open Enrollment Period is January 1 through March 31, 2027, and only for people already in a Medicare Advantage plan. Mixing them up is a common way to miss December 7.

Changes you can make

The changes you can make depend on the coverage you have now. People with Original Medicare can join, drop, or switch a stand-alone Part D plan. People in Medicare Advantage can switch Advantage plans, or return to Original Medicare. You generally need both Part A and Part B to join a Medicare Advantage plan. Confirm the choice on Medicare.gov.

  • Switch from Original Medicare to a Medicare Advantage plan.
  • Switch from Medicare Advantage back to Original Medicare.
  • Change from one Medicare Advantage plan to another.
  • Join, switch, or drop a stand-alone Part D plan if you have Original Medicare.
  • Choose a Medicare Advantage plan with or without drug coverage, if one is sold where you live.

Leaving Advantage is not the same as buying Medigap

If you return to Original Medicare, you may want a separate Part D plan, and you may want a Medicare Supplement. There are limits on when you can buy Medigap without health questions. California’s Birthday Rule is for people who already have a Supplement. It is not the path for leaving Advantage. See Can I switch from Medicare Advantage to Medigap?.

What to compare before you choose

A plan that fit in 2026 can still be the right one. The way to know is to compare the 2027 details against the care you already use. Start with the Annual Notice of Change and mark anything that touches medications, doctors, hospitals, dental or vision, referrals, or the monthly premium.

  • Prescriptions: whether each drug is covered, which tier it is on, and whether prior approval, quantity limits, or step therapy apply.
  • Pharmacy: the same drug can cost a different amount at a preferred pharmacy than at another one.
  • Doctors and hospitals: for Medicare Advantage, confirm the primary doctor, specialists, and hospital for 2027. “We take Medicare” is not a network answer.
  • Yearly cost: premium, deductible, copays, coinsurance, drug costs, and the Medicare Advantage out-of-pocket maximum.
  • Extras: dental, vision, hearing, rides, fitness, and over-the-counter allowances. They do not replace the doctors and drugs you need.
  • Travel: if you spend time in more than one state, ask how the plan treats non-emergency care outside the service area.

Original Medicare, Advantage, and Part D

Original Medicare is Part A and Part B, run by the federal government. Many people add a stand-alone Part D plan and, if they can buy one, a Medigap policy. Medicare Advantage (Part C) is another way to get Part A and Part B through a private plan Medicare approves. Those plans usually have networks and may include drugs and extras. The details depend on the plan and the county. Part D is the drug coverage, either as its own plan or inside many Advantage plans. Drug lists change, so Part D needs a fresh look every year. The published 2027 Part D numbers are in Medicare changes for 2027 and Medicare Part D in 2027.

The Annual Enrollment checklist

Use this checklist during the October 15–December 7, 2026 Annual Enrollment Period to review your coverage for 2027. Gather your doctors, prescriptions, pharmacy preferences, and current plan notices before comparing options. It does not enroll you or pick a plan. The annual review checklist is this same list in a form you can fill in.

  • Doctors I want to keep, including primary care and specialists.
  • Hospitals and facilities I already use.
  • Prescriptions, with the name, dose, and how often I take each one, and the pharmacy I use.
  • Oxygen, CPAP, a wheelchair, or other suppliers.
  • Travel I expect in 2027.
  • I read this year’s Annual Notice of Change for 2027 changes.
  • I compared options on Medicare.gov for my ZIP code.
  • I checked that those doctors, hospitals, and prescriptions are still covered.
  • I estimated the year, not only the premium.
  • If I make a change, I saved the confirmation number and the plan documents.

Mistakes that cost the year

Doing nothing does not freeze 2026. If you stay enrolled, the plan can still change costs and benefits on January 1. Choosing only by the premium is the other common miss: a low premium can cost more if a drug moves tiers or a doctor leaves the network. The third miss is treating January through March as a full do-over. That Medicare Advantage window allows one change, and only if you are already in an Advantage plan.

What a national 2027 update leaves open

CMS has published 2027 Medicare Advantage and Part D policy updates, including changes to quality measures, Star Ratings, and some enrollment processes, plus state landscape files. Those describe the market. They do not tell you whether a plan in your ZIP covers your doctor or your drugs. Star Ratings are one comparison point. A high rating does not replace a The plan’s drug list. It says which prescriptions are covered and which cost tier they are on. or a network check. Official sources are Medicare.gov, the Medicare & You handbook, and 1-800-MEDICARE (1-800-633-4227, TTY 711).