Medicare Open Enrollment Guide: What You Can Change and When

Medicare open enrollment is your once-a-year chance to change coverage without a qualifying life event, and the choices you make in this narrow window carry through the entire next plan year. The deadlines are fixed, and missing them means your current plan renews automatically with whatever premiums and benefits it has set for the coming year, whether or not that plan still fits your situation.

Deadlines you need to track every year

The main Medicare Open Enrollment Period runs October 15 through December 7 each year, and any changes made during this window take effect January 1. If you are already enrolled in a Medicare Advantage plan, you get a second window, the Medicare Advantage Open Enrollment Period, running January 1 through March 31, which allows you to switch plans or return to Original Medicare, though it does not allow you to switch from Original Medicare into a new Medicare Advantage plan. These dates do not flex for individual circumstances, so treat December 7 as a hard stop.

A step-by-step checklist for the enrollment window

Review your current plan first. Log into Medicare.gov or check the Annual Notice of Change letter that arrives from your plan in September or October, and note any shifts in premium, deductible, drug coverage, or network for the coming plan year specifically, not just the current one.

List every doctor, hospital, and prescription you actually use. Confirm your current or prospective plan includes your preferred providers in-network and that each medication appears on the formulary at a tier you can afford, since a plan can look cheap on premium alone while being expensive on your specific drug list.

Compare your structural options side by side. Original Medicare (Parts A and B) paired with a Medigap supplement and a standalone Part D drug plan is one path. Medicare Advantage (Part C), which bundles A, B, and usually D into one plan, is the other. Weigh monthly premium, deductible, out-of-pocket maximum, extra benefits like dental, vision, hearing, or gym membership, and the plan's star rating together, not any single factor in isolation.

Check whether you qualify for Extra Help or a low-income subsidy. If your income falls within the qualifying range, you may receive assistance with Part D premiums and drug costs, but you generally need to apply or reapply during this window rather than assuming a prior approval carries forward automatically.

Make the enrollment or change itself. Use Medicare.gov directly, call 1-800-MEDICARE, or work with a licensed agent, and keep every confirmation number and plan detail you receive during the process.

Verify coverage once the new plan year starts. New cards typically arrive by mail before January 1. Confirm your doctors and prescriptions are still processing correctly under the new plan year rather than assuming the transition went smoothly.

Mistakes that cost people money every year

Assuming your current plan is automatically still the best option for the coming year, when premiums, formularies, and networks can all shift annually without much notice. Focusing on the lowest premium without checking whether your specific drugs are covered at an affordable tier. Forgetting that Medicare Advantage plans carry networks and prior authorization requirements that Original Medicare simply does not have, which matters most if your health needs or preferred providers change mid-year.

Next steps with Bill Advantage

Use Bill Advantage's Health Insurance Plan Comparison tool (Member tier and above) to model Original Medicare against Medicare Advantage options side by side, using your actual doctors and prescriptions rather than generic estimates. Pair it with the Medicare Navigator for plain-English explanations of Part D and Medigap choices as you narrow down your decision.

---

Bill Advantage is a document literacy tool. Nothing in this article constitutes legal or medical advice.