Medicare and TRICARE: How They Work Together (2025)

Military retirees and their families who have TRICARE are entitled to one of the best Medicare supplement arrangements available — TRICARE For Life (TFL), which acts as secondary coverage to Medicare, paying most of what Medicare doesn't. But there's a non-negotiable requirement: you must enroll in Medicare Part B to maintain TRICARE For Life.

What Is TRICARE For Life?

TRICARE For Life is the Medicare supplement benefit available to military retirees, their spouses, and other eligible dependents who are entitled to Medicare. TFL is not a separate insurance plan you have to shop for or apply to — it is an automatic benefit that activates when you enroll in Medicare Part A and Part B.

Once you are enrolled in both Part A and Part B, TRICARE For Life kicks in as your secondary insurer. Medicare pays first; TFL pays second — covering most of the cost-sharing that Medicare leaves behind. For most Medicare-covered services, the result is $0 out-of-pocket cost for the beneficiary.

The Non-Negotiable Part B Requirement

This is the single most important fact for military retirees approaching Medicare age:

Because TRICARE For Life functions as a Medigap-equivalent supplement — covering your Part B deductible, your 20% coinsurance, and your Part A hospital deductible — the financial benefit of TFL is enormous. Losing it by dropping or failing to enroll in Part B is one of the costliest mistakes a military retiree can make.

How Cost-Sharing Works with TFL

Under the Medicare + TFL combination, costs are shared in a straightforward sequence:

1. Medicare pays primary — Medicare pays its standard 80% of approved charges after the Part B deductible is met
2. TFL pays secondary — TRICARE covers the remaining 20% (coinsurance) and the Part B annual deductible
3. You pay $0 — for most Medicare-covered services, the combined Medicare + TFL payment leaves nothing for the beneficiary to pay

Detailed Cost-Sharing Breakdown

TRICARE Pharmacy vs. Medicare Part D

Military retirees with TRICARE have access to the TRICARE Pharmacy benefit, administered through Express Scripts. This benefit provides prescription drug coverage that is generally equivalent to or better than Part D, at lower out-of-pocket costs. Drugs can be filled at military pharmacies (often at no cost), through the TRICARE Mail-Order Pharmacy, or at retail network pharmacies at low copays.

Critically, TRICARE drug coverage counts as creditable coverage for Medicare Part D. This means you do not need to enroll in a standalone Part D plan, and you will not face a Part D late enrollment penalty as long as you maintain TRICARE pharmacy coverage.

Most military retirees should not enroll in a separate Part D plan. The TRICARE pharmacy benefit is typically superior in both cost and formulary breadth. Adding a Part D plan on top of TRICARE pharmacy coverage adds premiums without meaningful benefit.

If you ever lose TRICARE coverage for any reason, you have 63 days to enroll in Part D without penalty. Keep that window in mind as a safety net.

TRICARE and Overseas Coverage

One area where TRICARE provides meaningful coverage that Medicare does not: care outside the United States. Medicare generally does not cover care received abroad (with narrow exceptions for care at a Canadian or Mexican hospital that is closer than a U.S. hospital in specific emergency situations). TRICARE covers care received overseas, which is a significant benefit for military retirees who travel internationally or live abroad.

Note: Standard Medigap plans G and N include a limited foreign travel emergency benefit (80% after a $250 deductible, up to a lifetime maximum of $50,000). But for military retirees with TFL, TRICARE's overseas coverage is far more comprehensive than what any Medigap plan offers.

TRICARE For Life vs. Medigap: Are They the Same?

Functionally, TRICARE For Life performs a role very similar to a Medigap (Medicare Supplement) plan — it pays Medicare's cost-sharing. But there are important distinctions:

For military retirees, TFL is the superior arrangement — broader coverage, no additional premium, and overseas coverage. There is no reason to purchase a Medigap plan if you have TFL. They perform the same supplemental function, but TFL does it at no added cost.

Should TRICARE Beneficiaries Enroll in Medicare Advantage?

This is one of the most important — and most commonly misunderstood — decisions for military retirees with TRICARE.

The short answer: for most TRICARE-eligible retirees, Medicare Advantage is the wrong choice. Here's why:

• TFL only coordinates with Original Medicare. TRICARE For Life is designed to pay secondary after Original Medicare pays primary. When you enroll in a Medicare Advantage plan, Original Medicare no longer processes your claims — the MA plan does. TRICARE cannot coordinate with a Medicare Advantage plan in the same way, which means your TFL supplemental benefit effectively does not apply to MA-covered services.
• You may lose the TFL supplement benefit. While you technically retain TRICARE For Life enrollment if you maintain Part B, the TFL benefit functions as a secondary payer to Original Medicare claims. For services covered by your MA plan, there are no Original Medicare claims for TFL to pay secondary on. The result: you may end up with MA plan cost-sharing (copays, deductibles) with no TFL payment to cover it.
• MA network restrictions can conflict with your care preferences. Medicare Advantage plans have provider networks and, in some cases, referral requirements. Original Medicare has no networks and no referrals. Military retirees who value the flexibility to see any provider — especially in combination with VA care — benefit from Original Medicare's openness.

The optimal arrangement for most military retirees: Original Medicare Part A + Part B + TRICARE For Life + TRICARE Pharmacy. This combination provides near-comprehensive coverage at very low out-of-pocket cost, with access to any Medicare-participating provider in the country.

TRICARE Enrollment Fees

TRICARE For Life itself does not have a separate monthly premium, but TRICARE coverage is not entirely free. Most military retirees pay a TRICARE enrollment fee for their TRICARE coverage (the amount varies by retiree category — retired pay, reserve retired, etc.). For TFL specifically, there is no additional enrollment fee beyond what you already pay for TRICARE. The cost of keeping TFL active is simply the Medicare Part B premium ($185.00/month in 2025 for most beneficiaries).

Frequently Asked Questions