If you are retired from a federal agency and keep FEHB, Medicare Part B is your choice. FEHB has no Part B requirement, and OPM says your FEHB premium "will not change when Medicare becomes primary". So the question is a straight trade: a monthly Part B premium in exchange for lower costs when you use care, plus some protection you can't buy back later without a penalty. (Postal retirees: see the PSHB Part B requirement first.)
What Part B costs
- $202.90 a month in 2026, the standard premium (CMS). CMS announces the 2027 premium in November; it usually goes up.
- More with IRMAA. With 2025 income (MAGI) above $109,000 single or $218,000 joint (2026 thresholds), you pay an income-related amount on top: from $81.20 to $487.00 a month in 2026. See IRMAA brackets 2027.
- Plus any late penalty, if you sign up after your Initial Enrollment Period without a Special Enrollment Period: 10% of the standard premium for each full 12 months, for life (OPM; Medicare.gov).
What Part B gets you
OPM lists three advantages for annuitants (OPM, Medicare and the annuitant):
- Reduced out-of-pocket costs. With Medicare paying first, many plans waive their deductible, copays and coinsurance for services Part B covers, and some reimburse part of the Part B premium (see plans that pay part of Part B).
- Broader coverage for items your plan may limit, such as durable medical equipment, orthopedic and prosthetic devices, home health care and medical supplies.
- A bigger network. In an FEHB HMO you can go outside the HMO for Part B services and be paid by Medicare, using any provider who accepts Medicare.
Most national FEHB fee-for-service plans waive their cost-sharing when Medicare pays first, but not all. FEP Blue Focus keeps its $1,000 deductible, and Aetna Advantage waives nothing with Original Medicare (it expects retirees to join its Medicare Advantage plan instead). Each 2027 brochure says which, in Section 9.
Worked examples for 2027
Yearly totals for one person, Self Only, with Part A, no IRMAA: the 2027 premium (your share, from OPM's rate tables) plus Part B ($202.90 a month, 2026 rate) minus any reimbursement, plus out-of-pocket costs for doctor visits, outpatient hospital care and a hospital stay from each plan's 2027 brochure. Prescription drugs aren't included.
Medium use: 4 primary care and 8 specialist visits, plus one outpatient hospital procedure or test
| Plan (Self Only) | Without Part B | With Part B | With its Medicare Advantage |
|---|---|---|---|
| Blue Cross and Blue Shield FEP Blue Standard | $6,411 | $7,756 | - |
| Blue Cross and Blue Shield FEP Blue Basic | $4,572 | $5,417 | - |
| GEHA High Option | $5,548 | $5,803 | - |
| APWU Health Plan High Option | $5,897 | $7,425 | $6,225 |
| Aetna Advantage | $4,461 | $5,312 | $3,066 |
High use: 6 primary care and 12 specialist visits, two outpatient hospital procedures, and one 4-day hospital stay
| Plan (Self Only) | Without Part B | With Part B | With its Medicare Advantage |
|---|---|---|---|
| Blue Cross and Blue Shield FEP Blue Standard | $6,856 | $7,756 | - |
| Blue Cross and Blue Shield FEP Blue Basic | $5,092 | $5,417 | - |
| GEHA High Option | $6,088 | $5,803 | - |
| APWU Health Plan High Option | $6,272 | $7,425 | $6,225 |
| Aetna Advantage | $7,037 | $7,608 | $3,066 |
Illustrative charges: $150 per primary care visit, $250 per specialist visit, $1,500 per outpatient hospital procedure, $20,000 for a 4-day stay. With Medicare paying first, you pay the plan's "with Medicare" amount, never more than Medicare leaves unpaid. Your numbers depend on your care, your income and your plan.
What the examples show
With Part A, most of these plans already waive a hospital stay, so for one person in a moderate year Part B usually costs more than it saves. It comes out ahead in some cases: a plan that pays back part of the premium, with heavy use (GEHA High Option here), or the plan's Medicare Advantage plan with a giveback and no cost-sharing (Aetna Advantage, and APWU High Option at high use). The examples leave out large outpatient bills, equipment and drugs, and the protection against a bad year that you can't buy back later without a penalty.
The part you can't undo: the penalty clock
Retiree FEHB is not coverage from current work, so it doesn't give you a Special Enrollment Period and doesn't stop the late-penalty count. You get one penalty-free window when you stop working: the 8 months after the job (or the job-based coverage) ends, whichever comes first (Medicare.gov; POMS HI 00805.275). After that, you can only sign up January 1 to March 31, with coverage from the next month, and pay the penalty for life. See how the late penalty is counted.
So the decision is not only this year's math. If you expect surgery, treatment for a chronic condition or other heavy outpatient care, Medicare paying first usually covers far more of it; if you skip Part B now, the cost of changing your mind grows every year.
OPM's tool won't do this math
OPM's FEHB Plan Comparison Tool shows each plan's premium and its cost-sharing with Medicare, including any Part B premium reimbursement. When we checked on October 27, 2026, it did not add the Part B premium or IRMAA, and did not compare your total cost with and without Part B. It still showed 2026 premiums under "Compare 2027"; OPM says 2027 data arrives in early November.
Should you take Part B with FEHB or PSHB in 2027?.Start the free FEHB/PSHB check