Medigap and Part D Together: How the Coverage Works

Why Medigap Doesn't Cover Prescriptions

Medigap plans sold after 2005 cannot include prescription drug coverage. Full stop. If your parent chooses Original Medicare with a Medigap supplement, they need a separate standalone Part D plan to cover medications—or they'll pay for every prescription entirely out of pocket and face a permanent late enrollment penalty if they sign up later.

This surprises families who assume Medigap's comprehensive cost-sharing coverage extends to prescriptions. It doesn't. Medigap covers Medicare's gaps—the Part A hospital deductible, Part B coinsurance, skilled nursing facility copays—but prescription drugs live in their own separate Medicare benefit with its own enrollment rules and penalties.

The Part D Late Enrollment Penalty

The penalty for delaying Part D enrollment is 1% of the national base beneficiary premium ($38.99 in 2026) multiplied by the number of full months your parent went without creditable drug coverage. That penalty gets added to their Part D premium every month for as long as they have Part D coverage.

Skip Part D for three years (36 months) and the penalty is roughly $14.00/month on top of whatever the plan premium is—permanently. The only exception is if your parent had other creditable drug coverage during the gap, such as from an employer or veterans' benefits.

Enroll during the Initial Enrollment Period or within 63 days of losing other creditable coverage. Don't wait.

How the Coverage Actually Stacks

Here's what your parent's three-part coverage looks like in practice:

Original Medicare (Parts A and B) pays first. It covers 80% of Part B services after the $283 annual deductible and handles hospital stays with cost-sharing that escalates the longer the stay.

Medigap Plan G pays second. It picks up everything Original Medicare doesn't for covered services—the 20% Part B coinsurance, Part A hospital deductible ($1,736 per benefit period), skilled nursing coinsurance ($217/day for days 21–100), and foreign travel emergencies. Your parent's total annual out-of-pocket for medical services is the $283 Part B deductible plus premiums.

Standalone Part D covers prescription drugs with its own premium, deductible (up to $615 in 2026, though many plans charge less), and copay tiers. The annual out-of-pocket cap is $2,100 in 2026 under the Inflation Reduction Act—once your parent hits that threshold, their drug costs drop to zero for the rest of the year.

The Medicare Prescription Payment Plan

If your parent takes expensive medications, the costs can be front-loaded early in the year when deductibles and initial copays hit. The Medicare Prescription Payment Plan smooths this out by spreading the annual drug costs into monthly installments.

It's free to enroll, doesn't change the total amount owed, and works like an interest-free payment plan. Instead of paying $525 at the pharmacy counter in January, the plan bills a manageable monthly amount that adjusts as costs accumulate. By the time the $2,100 cap is reached, remaining payments spread evenly over the rest of the year—stabilizing at around $190/month in a typical high-cost scenario.

Opt in through your Part D plan directly. There's no downside.

What Changes in 2027

The federal Part D Premium Stabilization Demonstration—which subsidized standalone drug plan premiums by $15/month in 2025 and $10/month in 2026—ends after 2026. That means standalone Part D premiums may increase in 2027 when plans return to operating without government premium offsets.

Medicare Advantage plans have a structural buffer here: they can use per-enrollee rebate dollars (averaging $2,400 in 2026) to subsidize their integrated drug coverage, often maintaining $0 drug premiums even as standalone plan costs rise. This is the one area where Medicare Advantage holds a genuine cost advantage over the Medigap path—but it comes packaged with network restrictions and prior authorization requirements for everything else.

Families choosing Medigap should budget for potential Part D premium increases starting in 2027 and compare standalone plans during each Annual Enrollment Period.

Our Medigap vs Medicare Advantage guide includes a cost comparison framework that accounts for Part D premiums, drug costs, and the Medigap premium to give your family the full annual picture for both coverage paths.

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