TRICARE For Life and Medicare: why you need Part B at 65

For military retirees, 65 is not just a birthday. It is the age when TRICARE stops being your main health coverage and becomes the second payer behind Medicare, through a program called TRICARE For Life. The switch is mostly smooth, but it comes with one rule that catches people every year: to keep TRICARE, you have to sign up for Medicare Part B and pay its premium.

I am on active duty in the Air Force, and this is the moment military families ask about years in advance. This guide uses the Centers for Medicare & Medicaid Services' own explanations, its booklet How Medicare Works with Other Insurance (February 2026) and its "Who pays first?" page, along with Medicare's pages on costs, penalties and enrollment. They are listed at the end. For TRICARE's own rules and claims, the booklet points you to tricare.mil/tfl or 1-866-773-0404.

What TRICARE For Life is

In Medicare's words, TRICARE For Life (TFL) provides expanded medical coverage to Medicare-eligible uniformed services retirees 65 or older, to their eligible family members and survivors, and to certain former spouses. It works alongside Medicare rather than replacing it: Medicare pays first for Medicare-covered services, and TRICARE may pay second.

The rule that matters: you need Part A and Part B

Medicare says it plainly: you must have Medicare Part A (Hospital Insurance) and Medicare Part B (Medical Insurance) to get TFL benefits. For Part A, CMS says approximately 99% of Medicare beneficiaries do not have a premium, because they have at least 40 quarters of Medicare-covered employment; military service has been covered employment since 1957. Part B is not free. For 2026, the standard Part B premium is $202.90 a month (more at higher incomes), and the yearly Part B deductible is $283.

Skipping Part B to save the premium is the expensive mistake. Without it, you lose TFL, and if you sign up later you can also owe a lifelong Part B late enrollment penalty.

Timing: when coverage starts

Because TFL depends on Part B being in force, the start date matters. Medicare's enrollment page explains it. Your Initial Enrollment Period lasts seven months: it starts three months before you turn 65 and ends three months after the month you turn 65. Coverage always starts on the first of a month:

Premium-free Part A starts the month you turn 65. Medicare adds one quirk: if your birthday is on the first of the month, coverage starts the month before. The practical lesson is to sign up in the three months before your birthday month, so Part B, and with it TRICARE For Life, starts on time and you are never left between programs.

Who pays first

Medicare's coordination rules for people with both Medicare and TRICARE:

That last row matters for retirees who live near a base. Medicare usually does not pay for services from a federal health care provider or other federal agency, so care at a military treatment facility is a TRICARE matter, not a Medicare one.

Prescription drugs

Drug coverage follows the same Part B rule. Medicare says most people with TRICARE who are entitled to Part A must also have Part B to keep their TRICARE drug benefits.

You do not need a separate Medicare drug plan. Medicare's guidance is that if you have TRICARE, you do not need to join a Medicare drug plan; if you do join one anyway, the Medicare drug plan pays first and TRICARE pays second, and the two can coordinate if the plan's network pharmacy is also a TRICARE network pharmacy. TRICARE is also on Medicare's list of drug coverage that can count as "creditable coverage", meaning coverage expected to pay, on average, at least as much as Medicare drug coverage, which is what protects people from the Part D late enrollment penalty. Your plan must tell you in writing whether your coverage is creditable, so keep that notice. Medicare's rule on timing is that with creditable coverage you can wait to join Medicare drug coverage without a penalty as long as you do not go without creditable prescription drug coverage for 63 days. If you ever drop TRICARE, that 63-day clock is the one to watch. For the TRICARE pharmacy program itself, the booklet lists 1-877-363-1303.

The Part B late enrollment penalty

Medicare's general rule is an extra 10% on the Part B premium for each full 12-month period you could have signed up but did not, and for most people it lasts as long as they have Part B. Its own example: someone who waited two full years without a Special Enrollment Period pays a 20% penalty, which in 2026 makes the monthly premium about $243.50 instead of $202.90.

Medicare does list a Special Enrollment Period for people who have TRICARE. On its enrollment page, the row for "Have TRICARE" says the period starts when Social Security notifies you and ends 12 months later, with coverage beginning the month after you sign up, or after the end of your Initial Enrollment Period if you choose. Generally, signing up during a Special Enrollment Period avoids the Part B penalty. The safest path is still the simplest one: enroll in Part B during your Initial Enrollment Period around your 65th birthday. Our guide to Medicare enrollment periods and guide to late enrollment penalties cover the windows in detail.

Still on active duty at 65?

A smaller group reaches Medicare age while still serving, or has Medicare earlier because of a disability. For them the order flips: while you are on active duty and have Medicare, TRICARE pays first and Medicare pays second. The Part B question is different for active-duty members, and it is one to settle with TRICARE and Social Security before you sign anything, using the TRICARE contacts above.

If you also use the VA

Many military retirees are also veterans with VA health care. Medicare and the VA do not coordinate the way Medicare and TRICARE do. In Medicare's words, if you have both Medicare and VA benefits you can get coverage under either program, but Medicare does not pay for care at a VA facility, and Medicare and the VA cannot pay for the same items or services. Each time you get care, you choose which coverage to use. Medicare pays for Medicare-covered services; the VA pays for VA-authorized services in a VA or authorized non-VA facility.

On drugs, you can use VA drug coverage or join a Medicare drug plan, but not both for the same drug at the same time, and joining a Medicare drug plan means you cannot use the VA's Meds by Mail program.

What it costs, and what it saves

For a retired couple both on Medicare, two Part B premiums at the 2026 standard rate come to about $4,870 a year, more if your income puts you in a higher bracket (see the IRMAA brackets). In exchange, Medicare pays first and TRICARE For Life may pick up costs Medicare leaves behind. The Part B premium page has the current amounts, and the 2027 figures will appear there once the Centers for Medicare & Medicaid Services announces them.

A checklist before 65

1. Mark your Medicare Initial Enrollment Period: seven months, starting three months before you turn 65 and ending three months after the month you turn 65.
2. Enroll in both Part A and Part B. TRICARE For Life requires both.
3. Budget for the Part B premium for each person in your household who is on Medicare.
4. You do not need a separate Medicare drug plan if you keep TRICARE; keep your creditable coverage notice.
5. If you are still on active duty at 65, ask TRICARE and Social Security about Part B before deciding.
6. If you use VA care, remember that each visit is covered by one program or the other, never both.
7. Make sure family members who are eligible for Medicare follow the same steps; TFL covers eligible family members and survivors too.

Medicare's materials explain how the programs work together; TRICARE's own pages and its contact centers decide individual cases. Confirm your situation with both before you turn 65.