Federal Employees Health Benefits

Medicare and FEHB Explained: Federal Employees and Retirees

Medicare and the Federal Employees Health Benefits Program can work together, but the rules change when you move from active federal employment to retirement. The most important questions are who pays first, whether to take Part B, how FEHB drug coverage works and how to protect your FEHB retirement rights.

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Written and reviewed by Benjamin Thompson, licensed Medicare brokerLast reviewed August 2026

Quick answer: If you are an active federal employee covered by FEHB, FEHB generally pays first and Medicare pays second. OPM says active employees can usually defer Medicare Part B until retirement and use the Part B Special Enrollment Period tied to current employment. If you are a federal annuitant, Medicare generally pays first for a Medicare-covered enrollee and FEHB pays second. You can keep FEHB whether or not you enroll in Part B, but retiree FEHB does not protect you from a future Part B late-enrollment penalty the way coverage based on current employment can.

The core idea

FEHB and Medicare Are Usually a Coordination Decision, Not an Either-Or Choice

Federal Employees Health Benefits coverage does not automatically end when Medicare begins. Many federal employees and retirees keep FEHB and use Medicare alongside it. The two coverages then coordinate based on Medicare Secondary Payer rules and your employment status.

The decision is different from a typical private-employer retirement question because FEHB can often continue into federal retirement if you satisfy OPM’s retirement-coverage rules. That makes it important to separate three issues:

Medicare enrollment

When should Parts A and B begin, and can Part B be delayed without a penalty?

Payer order

Is FEHB primary because you are still an active employee, or is Medicare primary because you are an annuitant?

Keeping FEHB

Do you meet OPM’s requirements to carry FEHB into retirement, and are you avoiding an irreversible cancellation?

This guide is FEHB-specific. It does not replace the broader rules in Can I Delay Medicare While Working Past 65? or the retirement timeline in Retiring After 65. Those pages cover general employer coverage; this page focuses on how Medicare coordinates with FEHB.

Who pays first?

Active Federal Employee vs. Federal Annuitant

Situation	Primary coverage	What that usually means
Active federal employee with FEHB	FEHB generally pays first	Medicare is secondary if you enroll. OPM says an active employee may defer Part B until retirement.
Covered spouse of an active federal employee	FEHB generally pays first for the Medicare-eligible spouse	The spouse’s Medicare can pay second while the employee remains actively employed and the spouse is covered under FEHB.
Federal annuitant enrolled in Medicare	Medicare generally pays first	FEHB becomes secondary for Medicare-covered services and may reduce some remaining cost sharing depending on the plan.
Spouse on an annuitant’s FEHB who is not Medicare-eligible	FEHB	Medicare coordination applies person by person; one spouse becoming Medicare-eligible does not put the other spouse on Medicare.

There are special situations—including reemployed annuitants, workers’ compensation, disability Medicare and ESRD—where the payer order can differ. If the situation is unusual, verify the order with OPM, the FEHB plan and Medicare rather than assuming.

Still working for the federal government

Should an Active Federal Employee Take Medicare Part A and Part B?

OPM treats Part A and Part B differently for many active federal employees.

Part A is often attractive when it is premium-free

Most Medicare-eligible workers qualify for premium-free Part A. OPM notes that Part A can sometimes pick up hospital-related expenses that FEHB does not fully pay. But there is an important HSA exception.

Part B can often be deferred while actively employed

Because FEHB is primary for an active federal employee, OPM specifically notes that an employee can save the Part B premium by deferring Part B until retirement and then using the Special Enrollment Period if eligible.

While you remain an active employee, paying a Part B premium may or may not create enough additional value to justify the cost. OPM notes that FEHB plans do not provide the annuitant-style Part B premium reimbursements or cost-sharing waivers while FEHB is primary for an active employee.

If you are deciding whether to delay Part B, use the dedicated CMS-40B and CMS-L564 Part B SEP guide and confirm the timing with your benefits office before retirement.

HSA warning

FEHB High-Deductible Plans Need Extra Medicare Planning

If your FEHB plan is HSA-qualified and you or your employer are contributing to a Health Savings Account, Medicare enrollment changes the tax rules. Medicare-covered months provide no HSA contribution allowance. A deposit for earlier eligible months may still be allowed by the applicable tax filing deadline if unused annual contribution room remains; employer deposits count toward the same limit.

The timing can be easy to miss because premium-free Part A can be retroactive for up to six months when someone enrolls after age 65, but not earlier than the first month of Medicare eligibility. OPM therefore warns people who delay Medicare while contributing to an HSA to plan well ahead of the eventual Medicare start date.

Do not start Part A casually if HSA contributions are still being made. See Medicare and HSA Rules for the contribution-stop timeline and discuss tax-specific questions with a qualified tax professional.

At retirement

What Changes When You Become a Federal Annuitant?

Once you retire from active federal employment, the coordination normally flips for a Medicare-covered retiree: Medicare pays first and FEHB pays second. That can make Part B more valuable than it was while you were working.

OPM says some FEHB plans may reimburse part of the Part B premium and some may waive deductibles, copayments or coinsurance for services that Medicare Part B covers. Those features are plan-specific; they are not a universal FEHB benefit.

At the same time, enrolling in Medicare does not automatically lower your FEHB premium. You still pay the FEHB premium for the plan and enrollment type you keep, plus any Medicare premium you owe.

Compare the combined premium

Add your FEHB annuitant premium and Part B premium, including any IRMAA, then subtract only a reimbursement that the official FEHB brochure actually provides.

Compare the combined cost sharing

Look at how the FEHB plan coordinates with Medicare—especially deductibles, office visits, outpatient care, hospital services and providers outside an HMO network.

Part B timing

Does Retiree FEHB Let You Delay Part B Forever Without a Penalty?

No. FEHB coverage as an annuitant is retiree coverage, not group health coverage based on current employment. The Part B Special Enrollment Period that protects many active workers is tied to current employment or a spouse’s current employment.

If you delayed Part B while you were an active federal employee, retirement is the point to coordinate the Part B SEP. If you are already retired and later decide you want Part B, you may have to use another Medicare enrollment opportunity and may owe a late-enrollment penalty if you do not qualify for an SEP.

FEHB itself does not require Part B for ordinary FEHB annuitants. The question is whether the additional Medicare coverage and FEHB coordination are worth the Part B premium—and whether delaying Part B creates a future penalty risk.

Prescription coverage

Do FEHB Members Need Medicare Part D?

OPM states that all FEHB plans provide creditable prescription drug coverage. That means you generally do not need to enroll in Medicare Part D simply to avoid the Part D late-enrollment penalty while you remain covered by FEHB.

If you do enroll in Part D, you can generally keep FEHB and the coverages coordinate. Whether adding Part D improves your specific drug costs is a separate comparison involving the exact FEHB plan, formulary, pharmacies, premiums and any income-related Part D adjustment.

For the underlying penalty rule, see Creditable Prescription Drug Coverage Explained. For annual drug-plan costs, see Medicare Part D Costs in 2026.

Protecting retiree coverage

Medicare Does Not Replace the FEHB Five-Year Retirement Rule

To carry FEHB into federal retirement, OPM generally requires that you retire on an immediate annuity and that you have been continuously enrolled—or covered as a family member—in FEHB for the five years of service immediately before retirement, or for all service since your first opportunity to enroll if that period is shorter.

Medicare enrollment does not waive that rule. If keeping FEHB in retirement matters to you, confirm your eligibility before changing or cancelling coverage.

Do not casually cancel FEHB as an annuitant. Cancellation can jeopardize the ability to return to FEHB. In certain circumstances an annuitant may be able to suspend rather than cancel FEHB, but that is an OPM retirement-benefits decision that should be verified before enrolling elsewhere.

Plan-level comparison

How Should a Federal Retiree Compare FEHB With Medicare?

There is no single answer for every federal retiree because FEHB plan designs differ. Use the official plan brochure for the exact plan and option you are considering—not only a summary chart.

What is the FEHB premium for Self Only, Self Plus One or Self and Family?
Will the plan reimburse any Part B premium for annuitants?
Which deductibles, copays or coinsurance are waived when Medicare is primary?
Do your doctors accept Medicare, and how does the FEHB network work after Medicare pays?
How are prescriptions covered, and would separate Part D add anything useful?
Does either spouse still need FEHB as primary coverage?
Will IRMAA increase the cost of Part B or Part D?
Are you considering an FEHB Medicare Advantage option or an outside Medicare plan that could affect FEHB enrollment?

If you are comparing Medicare Advantage with Original Medicare plus supplemental coverage, keep that structural decision separate from the FEHB coordination question. The Medicare Advantage vs. Medicare Supplement guide explains those Medicare structures without trying to replace your FEHB analysis.

Postal employees

FEHB and PSHB Are Not the Same Medicare Decision

Postal Service employees and annuitants generally moved from FEHB to the separate Postal Service Health Benefits Program beginning in 2025. PSHB has Medicare rules that can differ materially from ordinary FEHB—including Part B requirements for certain Medicare-eligible postal annuitants and family members.

If your coverage is through USPS, use the current OPM PSHB rules rather than applying this FEHB article to your situation.

Before retirement

A Federal Employee Medicare Checklist

1. Confirm FEHB retirement eligibility

Verify the immediate-annuity and five-year/all-opportunity requirements with your agency or OPM before making coverage changes.

2. Decide whether Part A should start

Premium-free Part A is often useful, but HSA contributors need to plan for Medicare’s retroactive Part A rules.

3. Plan the Part B SEP

If you delayed Part B while actively employed, prepare the required Medicare enrollment and employment-verification forms before the FEHB payer order changes.

4. Read the FEHB Medicare section

Check the current plan brochure for coordination, Part B reimbursement, cost-sharing waivers, drug coverage and any Medicare-specific plan option.

5. Compare the household

A spouse may remain on FEHB even when only one person enrolls in Medicare. Compare coverage person by person.

6. Keep the decisions separate

FEHB retirement eligibility, Medicare enrollment timing and private Medicare plan selection are related—but they are not the same decision.

Common questions

Medicare and FEHB FAQ

Do I have to enroll in Medicare Part B to keep FEHB?

Ordinary FEHB does not generally require a federal annuitant to enroll in Part B to keep FEHB. OPM says FEHB can continue whether or not you enroll in Medicare. Postal Service Health Benefits rules are different for certain Medicare-eligible postal annuitants.

Can I delay Part B while I am still a federal employee?

OPM says an active federal employee with FEHB can generally defer Part B while FEHB is primary and use the Part B Special Enrollment Period after active employment ends, assuming the Medicare SEP requirements are met.

Does my FEHB premium go down when Medicare becomes primary?

No. OPM states that enrolling in Medicare does not reduce your FEHB premium. Some FEHB plans may separately reimburse part of a retiree’s Part B premium, so check the exact plan brochure.

Is FEHB prescription coverage creditable for Medicare Part D?

Yes. OPM states that all FEHB plans provide creditable prescription drug coverage, so keeping FEHB can protect against the Part D late-enrollment penalty.

Does FEHB pay first after I retire?

For a Medicare-covered federal annuitant, Medicare generally pays first and FEHB pays second. FEHB remains primary for a covered family member who is not Medicare-eligible.

Should I cancel FEHB if I enroll in another Medicare plan?

Do not cancel FEHB without understanding the consequences. Annuitant cancellation can jeopardize future FEHB enrollment. OPM allows suspension in certain circumstances, but you should confirm eligibility and reinstatement rules before acting.

Are Postal Service retirees covered by the same FEHB rules?

Not necessarily. Postal Service employees and annuitants generally use PSHB beginning in 2025, and PSHB has separate Medicare Part B and drug-coverage requirements for certain retirees and family members.

More Medicare guidance

2026 costsMedicare Costs in 2026 Income-related premiumsWhat Is Medicare IRMAA?Drug coverageCreditable Prescription Drug Coverage

Official information

FEHB and Medicare Resources

Independent Medicare guidance

Compare Medicare Without Giving Up FEHB by Accident

We can help you compare the Medicare side of the decision—Part B timing, Medicare Advantage, Medigap and prescription coverage—while you verify FEHB eligibility and plan-specific rules with OPM and your federal benefits office.