FEHB and Medicare in Retirement: The Federal Employee's Guide

The question every federal employee asks around age 64: do I need Medicare Part B when I already have FEHB? Here's the real math — not the generic answer — for someone who spent a career in federal service.

Part 1: Keeping FEHB into retirement — the 5-year rule

To carry FEHB coverage past your last day of work, you must meet two conditions:

1. Enrolled for 5 consecutive years immediately before retirement — or since your earliest opportunity to enroll (whichever is shorter). Being covered counts — including coverage under your spouse's FEHB. You don't need to be the primary enrollee for all five years.
2. Retiring on an immediate annuity — your FERS or CSRS annuity must begin within 30 days of separation. (MRA+10 deferred retirements typically lose FEHB until the annuity starts.)

If you meet both conditions, FEHB continues into retirement under the same premium-sharing arrangement. The federal government still covers 72–75% of your premium — an extremely valuable benefit that most private-sector retirees lose the moment they leave their employer.

Part 2: Medicare Part A — take it, it's free

If you or your spouse worked at least 40 quarters in Social Security- or Medicare-covered employment, Medicare Part A (hospital insurance) has no monthly premium. There's no cost-benefit analysis: take it.

Part A covers inpatient hospital stays, skilled nursing facility care, hospice, and some home health care. Even with FEHB, a long hospitalization can generate significant cost-sharing. Part A as a secondary payer eliminates most of that exposure for free.

One note for CSRS employees: CSRS positions were not covered by Social Security. If your entire career was CSRS with no other Medicare-covered work history, you may not qualify for premium-free Part A. You can still purchase Part A (at $518/month in 2026 for zero quarters of coverage).¹ For most CSRS employees, this makes CSRS-only Part A enrollment not worth it — but run the specific numbers with your advisor.

Part 3: Medicare Part B — the decision that costs $2,400 a year

Part B covers outpatient care, physician services, preventive care, and durable medical equipment. The standard 2026 premium is $202.90/month.¹ Over a 20-year retirement, that's roughly $49,000 — before IRMAA surcharges if your income is above $109,000.

The question is whether the Part B coverage is worth that cost on top of FEHB.

How FEHB and Part B coordinate

When you have both FEHB and Medicare Part B, the coordination order is:

• Medicare Part B pays first (primary) for covered outpatient services — generally 80% of the Medicare-approved amount after the annual deductible.
• FEHB pays second (secondary) — often covering the remaining 20% and any cost-sharing your FEHB plan requires.

In practice, this means that for a doctor visit or outpatient procedure, your out-of-pocket cost can be near zero when you have both. Medicare pays 80%, your FEHB plan picks up most or all of the remaining 20%.

Without Part B: your FEHB plan is primary and covers the claim according to its own fee schedule — typically a copay or coinsurance. You're not left uncovered, but your out-of-pocket costs are higher than with the FEHB + Part B combo.

When Part B is clearly worth it

• You have a chronic condition or anticipate high outpatient utilization (regular specialist visits, ongoing treatments, infusion therapies).
• Your FEHB plan's outpatient cost-sharing is high — some FEHB plans waive deductibles and copays entirely for Medicare B enrollees (BCBS Service Benefit Plan Blue Focus, GEHA, Aetna Direct, and several others have Medicare B waivers).
• Your MAGI is below the first IRMAA tier ($109,000 single / $218,000 joint), so you pay the standard $202.90.
• You have a family member on FEHB who will also benefit from the coordination.

When Part B may not be worth it

• You're in excellent health, have low outpatient utilization, and your FEHB plan has low out-of-pocket maximums.
• Your income is above the IRMAA tiers (especially the higher tiers), making Part B cost $400–$690/month instead of $202.90.
• You're in a high-deductible FEHB plan (HDHP) paired with an HSA — once on Medicare, you can no longer contribute to an HSA, so you lose a tax advantage.

The late enrollment penalty

If you don't enroll in Part B when first eligible (at 65, or when FEHB-as-primary-coverage ends) and later decide you want it, you'll pay a permanent 10% premium surcharge per year you delayed. A 3-year delay means Part B costs 30% more for life — $263.77/month instead of $202.90 at 2026 rates.

Exception: if you're still actively employed and covered by FEHB as an active employee (not retiree FEHB), you qualify for a Special Enrollment Period when you retire. You can delay Part B while working without penalty, then enroll within 8 months of retirement. This is the relevant scenario for federal employees who retire after 65.

Part 4: IRMAA — how your pension and TSP withdrawals affect Part B costs

IRMAA (Income-Related Monthly Adjustment Amount) is a Medicare surcharge applied to high-income beneficiaries. It uses your MAGI from two years prior — so your 2026 Part B premium is based on your 2024 income.

Source: CMS, 2026 Medicare Parts A & B Premiums and Deductibles.¹

For federal employees, MAGI in retirement includes: FERS annuity (fully taxable), CSRS annuity (fully taxable), TSP withdrawals (fully taxable for traditional balances), Social Security (up to 85% taxable), and any investment income. A GS-15 SES retiree drawing a large annuity plus Social Security plus TSP distributions can easily land in the Tier 2 or Tier 3 IRMAA bracket — paying $365–$447/month for Part B instead of $202.90.

If you're already on Medicare and believe your income has dropped (retirement, death of spouse, divorce), you can appeal your IRMAA using Form SSA-44 to have the surcharge reassessed using more recent income. This is commonly overlooked — OPM reports that many federal retirees overpay IRMAA in the year they retire because SSA uses pre-retirement income.

Part 5: Medicare Part D — do you need it?

Part D is prescription drug coverage. Most FEHB plans include prescription coverage that qualifies as "creditable coverage" — meaning it's at least as good as standard Part D. If your FEHB plan's prescription coverage is creditable, you can decline Part D without incurring a late enrollment penalty later.

OPM confirms that most FEHB plans have creditable prescription drug coverage. Each year, your FEHB plan sends a notice confirming creditable status. If it says creditable, skipping Part D is generally correct — you're paying for duplicate coverage. Verify your specific plan's notice annually during open season.

Part 6: Which FEHB plans are best structured for retirees with Part B?

Several FEHB plans offer significantly enhanced benefits for enrollees who also have Medicare Part B — effectively eliminating most out-of-pocket costs. BCBS Service Benefit Plan (Blue Focus and Standard), GEHA High, and Aetna Direct are commonly cited for aggressive Medicare B coordination. These plans waive deductibles, eliminate or reduce copays, and sometimes eliminate the Part B 20% coinsurance entirely.

The right FEHB plan for retirement depends on your health profile, provider network, prescription needs, and whether you elect Part B. Open season (November–December each year) is your annual opportunity to optimize. Switching plans the year before retirement resets the 5-year clock consideration only for the new plan — but coverage under your current self+family FEHB as an active employee continues to count if you're switching within the FEHB system.

A federal-benefits specialist can model your specific out-of-pocket costs across 3–4 candidate FEHB plans given your expected healthcare utilization and whether Part B makes financial sense for your income level.

A concrete example: GS-14 retiring at 62

Suppose you're a GS-14 step 10 in a major metro area, annual salary approximately $155,000. You retire at 62 with 32 years of service, high-3 = $152,000.

• FERS annuity: 32 × 1.1% × $152,000 = $53,504/year (age 62+ multiplier of 1.1% applies).
• Social Security at 62: approximately $24,000/year (reduced from FRA benefit; exact amount depends on full earnings record).
• TSP: $800,000 traditional balance. No withdrawals initially — annuity + SS covers expenses.
• 2024 MAGI: annuity ($53,504) + SS taxable portion (~$20,400 at 85%) = approximately $73,900. Well below the $109,000 IRMAA threshold.

Part B decision: At $202.90/month, Part B makes strong sense. FEHB + Part B combo with a Part B-friendly plan (e.g., GEHA High) can eliminate almost all outpatient out-of-pocket. Net benefit is likely positive even accounting for the premium — particularly if health utilization is above minimal.

Watch for later: If this retiree begins TSP withdrawals of $40,000/year at age 73 for RMDs, MAGI rises to roughly $113,500 — above the first IRMAA tier. A $3/month distribution reduction could stay under $109,000. Worth modeling two years before RMDs begin.

Sources

1. CMS — 2026 Medicare Parts A & B Premiums and Deductibles: Part B standard premium $202.90/month; annual deductible $283; Part A premium $518/month (zero quarters). Published November 2025.
2. Kiplinger — 2026 IRMAA Brackets and Surcharges: first tier begins at $109,000 MAGI (single) / $218,000 (joint), based on 2024 income. Surcharges range $81–$407 above standard premium.
3. OPM — FEHB plan information and premium sharing: federal government pays approximately 72–75% of FEHB premiums for active employees and retirees.
4. OPM — FEHB and Medicare: FEHB continues as primary coverage for federal retirees who do not enroll in Part B; Medicare becomes primary when both are in force.

Medicare premium and IRMAA values verified against CMS publications and Kiplinger for 2026. FEHB rules verified against OPM. Current as of April 2026.