A federal retiree turning 65 is in an unusual position. Almost everyone else on Medicare needs Part B because they have nothing else. You already have FEHB for life, at the same premium an active employee pays, and nobody is going to take it away from you.
So the question is narrow and financial: is another $202.90 a month worth it on top of coverage you already have? Every figure below was pulled from CMS, Medicare.gov and OPM on September 6, 2026, using the 2026 plan year rates. The 2027 Part B premium does not exist yet (CMS normally releases it in November), and OPM’s own FAQ says 2027 FEHB rates land about a month before Open Season, so mid-October at the earliest.
Does FEHB Require You to Take Part B?
No. OPM says so directly on its Postal Service Health Benefits page, contrasting the two programs: there is no Medicare Part B enrollment requirement in FEHB. Your enrollment continues, your plan continues, and your family’s coverage continues whether you sign up for Part B or not.
Two other OPM statements matter here. First, enrolling in Medicare does not reduce or increase your FEHB premium. You will pay the same $408.02 a month for Blue Cross Standard Option Self Only in 2026 whether or not you also carry Part B. Second, most people pay nothing for Part A, so taking Part A at 65 is close to a free decision. Part B is the one with a bill attached.
One exception worth flagging: if you are still working and contributing to an HSA through an FEHB high-deductible plan, OPM warns you must stop contributions at least six months before you enroll in Part A or Part B to avoid a tax penalty.
The Part B mandate people have heard about is real, but it belongs to a different program. Postal employees and annuitants moved to PSHB in 2025, and most Medicare-eligible postal annuitants there are required to take Part B.
Who Pays First When You Have Both
Order of payment is set by Medicare, not by your carrier, and it flips at retirement.
While you are an active federal employee with FEHB, your FEHB plan is the primary payer and Medicare pays second. That is why there is no rush to take Part B at 65 if you are still working. Once you become an annuitant, Medicare Parts A and B become primary and FEHB becomes secondary. The Blue Cross Service Benefit Plan’s 2026 brochure lays this out in a primary payor chart that matches OPM’s rules exactly.
A common household split: you retire and take Part B, your younger spouse is still under 65. Medicare is primary for you, FEHB is secondary for you, and FEHB stays primary for your spouse.
What Part B Costs in 2026
CMS published the 2026 numbers on November 14, 2025. The standard premium rose $17.90 to $202.90 a month, and the annual Part B deductible rose $26 to $283.
Roughly 8% of people with Part B pay more because of the income-related monthly adjustment amount. IRMAA for 2026 is based on your modified adjusted gross income from your 2024 tax return.
| 2026 Part B: your 2024 MAGI | Single filer | Joint filers | Total monthly premium | Cost per year |
|---|---|---|---|---|
| Standard | $109,000 or less | $218,000 or less | $202.90 | $2,434.80 |
| Tier 1 | Over $109,000 to $137,000 | Over $218,000 to $274,000 | $284.10 | $3,409.20 |
| Tier 2 | Over $137,000 to $171,000 | Over $274,000 to $342,000 | $405.80 | $4,869.60 |
| Tier 3 | Over $171,000 to $205,000 | Over $342,000 to $410,000 | $527.50 | $6,330.00 |
| Tier 4 | Over $205,000 to under $500,000 | Over $410,000 to under $750,000 | $649.20 | $7,790.40 |
| Tier 5 | $500,000 or more | $750,000 or more | $689.90 | $8,278.80 |
Source: CMS 2026 Medicare Parts A and B fact sheet. Those are per-person figures, so a married couple both on Part B doubles them.
The jump from the standard tier to Tier 1 is $81.20 a month, or $974.40 a year, triggered by one dollar of MAGI over the threshold. A retirement-year Roth conversion or a large capital gain in 2024 can put you there. IRMAA is appealable when the income was a one-time event or your circumstances changed, which is covered in how to appeal Medicare IRMAA.
The Penalty If You Skip Part B and Want It Later
This is the part that makes the decision feel permanent, and mostly it is.
Medicare charges 10% of the standard premium for each full 12-month period you could have had Part B and did not, and you pay it for as long as you have Part B. Medicare’s own 2026 example: wait two full years without a Special Enrollment Period and you pay a 20% penalty, so $243.50 a month instead of $202.90.
Apply the same formula to a longer delay and the numbers get uncomfortable. Five years late is a 50% penalty, roughly $101 a month on top of the standard premium, for life. OPM confirms the rule on its annuitant page and adds a second cost: limited enrollment windows, so there may be a gap of months before coverage starts.
There is an important protection while you are still working. FEHB from current federal employment is employer coverage, which is why OPM tells retiring employees to have their retirement system complete form CMS L564 so they can use a Special Enrollment Period rather than pay a penalty. Deferring Part B while you are on the payroll is normal and penalty-free. Deferring it after you retire is what starts the clock. Full detail lives in the Medicare late enrollment penalty guide.
What Your FEHB Plan Gives Back If You Take Part B
The case for paying the premium rests on what your carrier does in return, and it varies by plan and option. Check your own brochure, because these are contract terms, not general rules.
Take the largest plan in the program as the worked example. The Blue Cross and Blue Shield Service Benefit Plan’s 2026 FEHB brochure says that when Medicare Part B is primary, Standard Option waives its calendar-year deductible, its coinsurance and copayments for inpatient and outpatient physician services, and its coinsurance for outpatient facility services. Basic Option waives copayments and coinsurance for care from covered professional and facility providers. Neither waives prescription drug cost sharing or benefit limits.
Blue Cross also runs a Medicare Reimbursement Account. Basic Option members enrolled in both Part A and Part B can be reimbursed up to $800 per calendar year for Part B premiums they paid. That turns $2,434.80 of Part B premium into a net $1,634.80.
OPM’s annuitant page confirms the wider pattern: some FEHB plans reimburse Part B premiums, many waive copays and coinsurance when Part B is primary, and Medicare Advantage plans offered through FEHB plans often reimburse some or all of the Part B premium. If you are in an FEHB HMO, taking Part B also lets you go outside the network and be paid by Medicare for Part B services.
Run your own arithmetic before Open Season using the FEHB premium tables, because switching options is often worth more than the Part B decision itself.
Part D and Your FEHB Drug Benefit
You do not need a standalone Part D plan, and buying one can actively hurt you.
OPM states that FEHB provides creditable drug coverage, so deferring Part D carries no late enrollment penalty as long as you keep FEHB. Separately, OPM’s January 2023 carrier letter pushed FEHB carriers toward Part D Employer Group Waiver Plans so members could capture the Inflation Reduction Act’s manufacturer discounts, the $35 insulin cap, and the $2,000 annual cap on out-of-pocket drug costs. Many plans now do exactly that.
Blue Cross’s 2026 brochure says Medicare-enrolled members who are not in a Medicare Advantage plan are automatically enrolled in the plan’s PDP EGWP, that benefits will never be worse than the regular FEHB drug benefit, and that participation is voluntary with an opt-out available at any time.
The trap: you can only be in one Part D or Medicare Advantage plan at a time. Buying an outside Part D plan can disenroll you from the drug benefit built into your FEHB plan. If drug costs are your problem, look at Medicare Extra Help before shopping standalone plans.
Who Should Take Part B, and Who Should Skip It
Take Part B if your FEHB plan waives deductibles, coinsurance and copays when Part B is primary, and especially if it reimburses part of the premium. On Blue Cross Basic Option, the effective cost is about $136 a month after the $800 refund, in exchange for near-zero cost sharing on medical care.
Take it if you use a lot of care, travel or live part of the year away from your plan’s network, are in an HMO whose network is tight, or want coverage for items Part B pays for that your plan limits, such as durable medical equipment.
Skip it, or at least think hard, if you are in the standard IRMAA tier but healthy and low-utilizing, if your plan does not waive cost sharing for Medicare-primary members, or if you are in a top IRMAA tier where two spouses on Part B can cost more than $16,000 a year. Also skip it if you are still working federally, where FEHB pays first anyway and a Special Enrollment Period protects you later.
The decision is not quite one-way. You can change FEHB plans every Open Season, and becoming Medicare-eligible is itself a qualifying life event that lets you switch once. But the Part B penalty never goes away, so treat “skip it” as a choice you may be living with for 20 years.
For the rest of the retirement picture, including the five-year rule and how premiums come out of your annuity, see FEHB in retirement.