Medigap vs. Part D: Why Only One Needs Your Focus Now

If you carry a Medicare Supplement (Medigap) plan and a separate Part D drug plan, here is the short version for this year's Open Enrollment: your Medigap plan does not change and needs no action, but your Part D drug plan almost certainly does. The confusion between the two is what drives most of the anxiety seniors feel every October — and it is avoidable once you know which half of your coverage actually moves.

Why Your Medigap Plan Doesn't Change Each Year

Every Medigap policy issued since 1992 is guaranteed renewable — the insurer cannot drop you or change your benefits based on your age, health, or claims history as long as you pay the premium (Medicare). That guarantee is exactly what makes supplemental coverage the stable half of your Medicare picture.

What's Actually Changing With Part D in 2027

Part D is the half of your coverage that moves. Unlike Medigap, a standalone Part D plan (a PDP) is guaranteed renewable in name only — its benefits, premiums, and formularies can change significantly from one year to the next (medicareresources.org). That is why the annual review exists.

There are genuinely good updates to watch for too. Starting January 1, 2027, negotiated maximum fair prices take effect for 15 high-cost Part D drugs used to treat conditions like cancer and diabetes, projected to save Medicare patients about $685 million in out-of-pocket costs (ElderLawAnswers). A plan that did not cover one of these drugs well last year may be far more attractive now — the kind of change you only catch by looking.

A Simple Next-Step Checklist

You do not need a Medicare expert to act on this — a short annual review is enough. When your Annual Notice of Change (ANOC) letter arrives in late September, follow these steps:

1. Read the letter from YOUR Part D plan for premium, formulary, and coverage changes effective January 1.

2. Recheck your specific medications against the new formulary — confirm no drug is being dropped, moved to a higher tier, or restricted.

3. Compare 2–3 available PDPs using the Medicare Plan Finder, weighing monthly premium against your actual prescriptions.

4. Keep your Medigap policy untouched — switching or adding it is not part of Open Enrollment.

5. Make any Part D switch by December 7 for coverage starting January 1.

Why This Distinction Matters

Clear heads win Open Enrollment. The single most common source of AEP anxiety is the mistaken belief that a changing drug market destabilizes your supplemental coverage. It does not. Your Medigap foundation is guaranteed renewable and stays exactly as it is, while a separate, contained decision about your Part D plan does all the real work. That separation is what lets you review with confid…

At The Integrity Agency, a Dover, NH Medicare agency, we have spent ten years helping residents sort exactly this — which piece of their Medicare needs attention and which can be safely left alone. If you would like a second set of eyes on your annual Part D notice before December 7, that is the kind of call we are here for — book your appointment now on our website, and we will walk through your coverage step by step.