What Should You Know About Medicare Open Enrollment for 2027?
The October to December window, what you can change, why the annual notice of change matters and how to compare drug coverage without guessing.
Quick Answer
What you should know about Medicare open enrollment first is the calendar: it runs from October 15 to December 7 each year, and changes made in that window take effect on January 1 of the following year. For coverage starting in 2027, that is the autumn 2026 window.
During it you can switch between Original Medicare and Medicare Advantage, change Advantage plans, and join, drop or switch a Part D drug plan.
The document that should drive your decision arrives in the post around September. It is called the annual notice of change, and it lists exactly what your current plan is altering for next year.
What You Can and Cannot Change
| Change | Allowed in open enrollment? |
|---|---|
| Original Medicare to Medicare Advantage | Yes |
| Medicare Advantage back to Original Medicare | Yes |
| Switch from one Advantage plan to another | Yes |
| Join, drop or switch a Part D drug plan | Yes |
| Buy a Medigap policy with guaranteed acceptance | Not generally, this has its own rules |
The Medigap exception catches people out. Supplemental policies have their own enrollment protections, largely tied to when you first enrolled in Part B, and outside those protected periods insurers in most states can use medical underwriting. If you are considering leaving Medicare Advantage for Original Medicare plus a Medigap policy, check acceptance rules before you cancel anything.
Read the Annual Notice of Change
Every Advantage and Part D plan must send members a notice each autumn describing what changes for the coming year. It is the single most useful document in the process and the one most likely to go straight into a drawer.
- Premium and deductible changes for next year.
- Copay or coinsurance changes for doctor visits, specialists and hospital stays.
- Formulary changes, meaning drugs added, dropped or moved to a different cost tier.
- Network changes, meaning providers or pharmacies joining or leaving.
- Changes to extra benefits some plans include.
A plan that suited you perfectly this year can become the wrong plan next year without you doing anything at all, purely because a drug moved tier or a hospital left the network.
Start From Your Drug List
For most people, prescription costs are the largest variable, and comparing plans on premium alone is the most common expensive mistake. A cheaper premium with a worse formulary regularly costs more over a year.
Write down every medication with its exact dose and monthly quantity, then enter that list into the official plan comparison tool. It will estimate total annual cost including premiums, deductible and each drug at each plan's pricing, which is the number that actually matters.
Do the same for your preferred pharmacy. Many plans have preferred pharmacy pricing that is meaningfully cheaper than standard network pricing for the identical drug.
Check Your Doctors Every Year
Advantage plan networks change annually. A physician or hospital in network this year may not be next year, and the notice of change does not always make that obvious in a way you will notice.
Verify with the plan directly and with the provider's office. Provider directories are frequently out of date, so two sources beats one. If you split your year between two places, check whether the plan covers routine care away from home or only emergencies.
A Sensible Timeline
Spreading the work over several weeks makes it far less daunting than a single December afternoon.
- September: read the annual notice of change when it arrives, and highlight anything affecting your drugs or doctors.
- Early October: write out the current medication list and confirm your doctors and pharmacy.
- October 15 onward: run the comparison, look at total annual cost rather than premium.
- Late October: make the change if one is warranted, rather than waiting for the deadline crush.
- December 7: final deadline. Nothing good happens by leaving it to this date.
- January: check the first pharmacy fill and the first claim under the new plan and query anything unexpected immediately.
Free Help That Is Genuinely Independent
Every state runs a State Health Insurance Assistance Program offering free, unbiased counseling. Counselors are not paid commission on plan selection, which distinguishes them from many phone lines and mailers that arrive at this time of year.
Be cautious with unsolicited marketing calls during the enrollment window. Legitimate Medicare will not cold-call to sell you a plan, and nobody legitimate needs your Medicare number over the phone in an unsolicited call.
If You Change Your Mind
There is a separate Medicare Advantage open enrollment period from January 1 to March 31. During it, someone already in an Advantage plan can switch to a different Advantage plan or return to Original Medicare and join a drug plan. It is a useful safety valve, but it is narrower than the autumn window, so it should not be your primary plan.
The Mistakes That Cost People Money
Most enrollment regret comes from a handful of repeated errors rather than from genuinely difficult judgment calls.
Doing nothing is the biggest one. Automatic renewal feels like stability, but it renews you into next year's version of the plan, which may have a different formulary, a different network and a higher deductible than the one you chose.
Choosing on premium alone is the second. A plan with a low monthly premium and an unfavourable drug tier structure can cost hundreds more across a year than a slightly pricier alternative.
Assuming your doctor is still in network is the third. Networks change annually and directories lag, so a two-source check is worth the ten minutes it takes.
Overlooking pharmacy pricing is the fourth. The same drug on the same plan often costs meaningfully less at a preferred pharmacy than a standard one, and switching pharmacies is easier than switching plans.
Finally, responding to unsolicited calls and mailers rather than starting from the official comparison tool leads people into plans chosen for someone else's convenience. Start from your own drug list and your own doctors, then let the numbers decide.
Frequently Asked Questions
When is Medicare open enrollment? October 15 to December 7, with changes effective January 1.
What can you change during it? Between Original Medicare and Advantage, between Advantage plans, and joining, dropping or switching Part D drug coverage.
What is the annual notice of change? The document your plan sends each autumn listing next year's premium, cost and coverage changes.
Should you compare on premium alone? No. Compare estimated total annual cost including your specific drugs at your specific pharmacy.
Can you buy Medigap during open enrollment? Not with the same guarantees. Medigap has separate enrollment protections and may involve underwriting.
Is there free help available? Yes, through your State Health Insurance Assistance Program, which offers unbiased counseling at no cost.