What is the first Medigap trap?

Paying twice. Medigap exists to fill the gaps in Original Medicare. But your FEHB plan already fills those same gaps when it coordinates with Medicare. Adding a Medigap policy layers a second supplement on top of one you already have, so you pay a second premium for coverage you are largely already receiving. FEHB is also usually cheaper than a comparable Medigap policy and covers dependents, which Medigap never does.

What is the second Medigap trap?

Dropping FEHB to switch to Medigap plus Part D. This is the dangerous one because it is effectively a one-way door. Cancelling FEHB in retirement is generally irreversible — you usually cannot re-enroll later. You would also lose coverage for your dependents, the option for a survivor to keep the plan, and FEHB's dental and vision choices. Unless the numbers are overwhelming and permanent, giving up FEHB to save on premiums is a trade most retirees regret.

Does FEHB replace Medigap and Part D?

Yes to both, for most retirees. FEHB serves the Medigap role by paying what Medicare doesn't, and all FEHB plans include prescription drug coverage that is at least as good as Medicare Part D, so you generally do not need a separate Part D plan either. Enrolling in Part D on top of FEHB is usually another way of paying twice. The main separate decision worth real analysis is whether to take Medicare Part B, which is a different question from Medigap.

When might Medigap actually make sense for a federal retiree?

Rarely, and only after careful math. If your FEHB retiree premium is unusually high relative to a Medigap Plan G premium, or you need nationwide any-provider access that a narrow FEHB network doesn't give you, dropping FEHB for Medigap plus Part D could theoretically save money. But because leaving FEHB is generally permanent and costs you dependent and survivor coverage, this only makes sense in narrow cases and should be run past a benefits specialist before you cancel anything.

FEHB & Medicare Medicare

Do federal retirees even need Medigap?

Q: Do federal retirees need Medigap?

Generally, no. If you keep your FEHB plan into retirement, it already acts as a Medicare supplement. With Medicare paying primary and a comprehensive FEHB plan paying secondary, most covered costs — the Part B deductible and the 20 percent coinsurance Original Medicare leaves behind — are picked up by FEHB, often producing coverage equal to or better than a Medigap Plan G. Buying a separate Medigap policy on top of FEHB means paying twice for the same gap-filling role.

Short answer: almost never. If you carry FEHB into retirement, you already have a Medicare supplement — one that often matches or beats a Medigap Plan G. The real risk isn’t going without coverage; it’s falling into one of two Medigap traps that cost federal retirees money or, worse, their FEHB.

By Anshul Meena • Published July 25, 2026 • 7 min read

≥ Plan G

Coverage FEHB + Medicare often equals or beats

Coordination of benefits

Medigap traps to avoid

This guide

Part D you need — FEHB drug coverage is creditable

OPM

1-way

Dropping FEHB in retirement is generally irreversible

The big risk

1. What Medigap is, and why it exists

Original Medicare (Parts A and B) is good coverage, but it leaves holes: a Part A hospital deductible, a Part B deductible, and a permanent 20% coinsurance on most Part B services with no annual out-of-pocket cap. For a retiree with no other coverage, that 20% on a serious illness can run into five figures.

Medigap — also called Medicare Supplement insurance — is a private policy that plugs those holes. Plan G, the most popular version, covers essentially everything except the small Part B deductible. It’s a sensible purchase… for a retiree who has only Original Medicare. A federal retiree with FEHB is not that person.

2. Why FEHB already is your Medigap

Here’s the key fact most retirees miss: when you have both Medicare and FEHB, they coordinate. Medicare pays first, and your FEHB plan pays second — picking up the deductibles and the 20% coinsurance that Medicare leaves behind. In other words, FEHB performs the exact job Medigap is sold to do.

FEHB (with Medicare) vs. buying a separate Medigap policy
What matters	FEHB + Medicare	Separate Medigap
Fills Medicare’s gaps	Yes — often ≥ Plan G	Yes
Prescription drugs	Included (creditable)	Need separate Part D
Covers your dependents	Yes	No — one person per policy
Government pays part of premium	~72% for life	You pay 100%
Dental / vision options	Available (FEDVIP)	Not included

Some FEHB plans go further, offering Medicare-coordination options that waive cost-sharing or even reimburse part of your Part B premium when you enroll in Medicare. The takeaway is the same: for a federal retiree, FEHB isn’t a step down from Medigap — it’s usually a step up.

3. Trap 1: Paying twice

The first trap is buying a Medigap policy on top of FEHB. Because FEHB already fills Medicare’s gaps, a separate Medigap policy layers a second supplement over one you already have. You pay a second premium — entirely out of pocket, since the government subsidizes FEHB but not Medigap — for coverage you’re largely already getting.

The same logic applies to Part D. Every FEHB plan includes drug coverage that Medicare deems “creditable,” so signing up for a standalone Part D plan is usually another way of paying twice. The one Medicare piece that genuinely deserves its own analysis is Part B — but that’s a separate decision from Medigap.

Watch for the sales pitch

Medigap and Part D are heavily marketed to everyone turning 65. Those pitches aren’t written for federal retirees. Before you buy anything, remember that your FEHB plan already does the supplement job — and covers your spouse, which Medigap can’t.

4. Trap 2: Dropping FEHB — the one-way door

The second trap is the costly one. Some retirees look at their FEHB premium, compare it to a Medigap Plan G premium, and decide to drop FEHB and go Medigap-plus-Part-D instead. On a spreadsheet it can look like a saving. In reality it’s often a decision you can’t undo.

Cancelling FEHB in retirement is generally irreversible — you usually can’t re-enroll later, no matter how your health or the Medigap market changes. And you don’t just lose the plan; you lose:

What you give up by dropping FEHB
You lose	Why it stings later
The government subsidy	~72% of premium you’ll never get back — you now pay 100% of a Medigap policy
Dependent coverage	Medigap covers one person; a spouse or dependent loses their coverage
The survivor’s coverage	A surviving spouse can normally keep FEHB — but only if you never dropped it
Re-entry	Changed your mind? Generally too late — FEHB re-enrollment after dropping it is rarely allowed

Medigap saves you a premium today. Dropping FEHB to get it can cost your spouse their coverage, your survivor their plan, and you any way back in. That’s a bad trade for almost everyone.

5. When Medigap might make sense

Almost never — but “almost” isn’t “never,” so here’s the honest edge case. Dropping FEHB for Medigap-plus-Part-D could theoretically pay off if both of these are true and durable: your FEHB retiree premium is unusually high relative to a Plan G premium, and you value Medigap’s nationwide, any-provider access over a narrower FEHB network. Even then, run it past a federal benefits specialist first, because the move is permanent and the lost dependent and survivor coverage rarely shows up in the premium comparison.

6. What most feds should do

For the large majority of federal retirees, the plan is simple: keep FEHB, add Medicare Part A (it’s premium-free if you or your spouse paid in for 10+ years), make a deliberate decision about Part B, and skip Medigap and Part D entirely. That combination gives you comprehensive, subsidized, dependent-covering coverage that a standalone Medigap policy simply can’t match — and it keeps every door open.

The one-line rule

You already bought your Medigap — it’s called FEHB. Don’t buy it again, and don’t trade it away.

7. FAQ

Do federal retirees need Medigap?

Generally no. FEHB carried into retirement already acts as a Medicare supplement — Medicare pays first, FEHB picks up the deductible and 20% coinsurance, often equaling or beating Plan G. A separate Medigap policy means paying twice for the same job.

What's the first trap?

Paying twice — buying Medigap on top of FEHB, which already fills Medicare’s gaps. FEHB is usually cheaper than Medigap, is subsidized by the government, and covers dependents, which Medigap never does.

What's the second trap?

Dropping FEHB to switch to Medigap plus Part D. It’s a one-way door: FEHB re-enrollment is generally not allowed, and you lose the premium subsidy, dependent coverage, and a survivor’s ability to keep the plan.

Does FEHB replace Part D too?

Yes. All FEHB plans include creditable prescription coverage, so a separate Part D plan is usually redundant. The one Medicare piece worth its own analysis is Part B — a different decision from Medigap.

When might Medigap make sense?

Rarely — only if your FEHB premium is unusually high versus Plan G and you need nationwide any-provider access, and only after a benefits specialist confirms the permanent trade-offs are worth it.

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