Medicare Open Enrollment Opens Oct 15: 2027 Math

Medicare's annual enrollment period opens tomorrow, October 15, and runs through December 7, 2026, with changes taking effect January 1. This is not a repeat of a planning reminder. The Centers for Medicare & Medicaid Services (CMS) has now published its 2027 premium projections, and they point in two directions at once: Medicare Advantage gets cheaper on average, and stand-alone drug coverage gets slightly more expensive. If you or a parent are enrolled, the next eight weeks are when that math becomes personal.

The headline numbers from CMS

CMS projects the weighted-average monthly Medicare Advantage premium will fall 16.5 percent, from $14.37 in 2026 to $12.00 in 2027. The drug portion inside Advantage plans falls much further, from $11.32 to $7.00 a month, a drop of about 38 percent. Stand-alone Part D tells the opposite story in miniature: the average premium rises from $35.09 to $36.00, an increase of $0.91 a month, or about $10.92 a year.

CMS also said about 8 in 10 Advantage beneficiaries should be able to stay in their current plan at the same premium or a lower one, that more than 99 percent of beneficiaries will still have at least one Advantage plan available, and that 97 percent will have 10 or more to choose from. Averages are a starting point, not a decision. Your plan's own notice is the decision document.

Figure: CMS premium projections for 2027 against 2026. Source: Centers for Medicare & Medicaid Services 2027 projections, reported by AJMC and Morningstar, September-October 2026.

Why Part D is drifting up while Advantage falls

One reason is in CMS's own explanation, reported by AJMC: a temporary program that held stand-alone Part D premiums down, the Part D Premium Stabilization Demonstration, ends after 2026. When a subsidy ends, the premium does not jump all at once in this case - it edges up by less than a dollar on average - but the direction tells you the support is gone. Advantage plans, which bundle medical and drug coverage and receive rebates, are moving the other way for 2027.

I would not chase the average. A $12 average Advantage premium tells you nothing about whether your doctors stay in network or your prescriptions stay on formulary in January. Those two checks are worth more than any premium saving.

My shopping order for the next eight weeks

First, find the Annual Notice of Change your plan sent. It lists your 2027 premium, deductible, copays, and coverage changes in one place. Second, list your current prescriptions exactly as written and check each one against any plan you are considering, including the pharmacy tier. Third, check your regular doctors and hospital against the network, not a brochure. Fourth, only then compare premiums, using the chart above as a sanity check: if your Advantage premium is rising while the national average falls 16.5 percent, that is a specific reason to shop, not a reason to panic.

Fifth, mind the calendar. Changes must be made by December 7, and they start January 1 whether you are ready or not. Free, unbiased help exists through your State Health Insurance Assistance Program, and Medicare's own plan comparison tool uses your drug list rather than national averages.

What this is worth, honestly

For an Advantage member whose premium follows the average, the saving is about $28.44 a year on the plan premium, plus a larger drop in the embedded drug portion. For a stand-alone Part D member, the cost is about $10.92 a year more. Neither figure changes a retirement. What changes a retirement is a drug moved to a higher tier or a doctor leaving a network unnoticed in October and discovered in February. Spend your enrollment time there.

FAQ

When is Medicare open enrollment for 2027 coverage? October 15 through December 7, 2026, according to CMS, with changes effective January 1, 2027.

How much are Medicare Advantage premiums projected to change? CMS projects the weighted-average monthly premium falls 16.5 percent, from $14.37 to $12.00, in 2027.

Are Part D premiums going up or down? Stand-alone Part D rises slightly on average, from $35.09 to $36.00 a month, while the drug portion inside Advantage plans falls from $11.32 to $7.00, per CMS.

Why is stand-alone Part D rising? CMS is ending the temporary Part D Premium Stabilization Demonstration after 2026, according to AJMC's reporting of the CMS release.

Where can I get free help comparing plans? Your State Health Insurance Assistance Program offers free counseling, and Medicare's plan finder compares plans using your own prescriptions.