TRICARE East vs. West: which region am I in?
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Your region decides which company runs your benefit, which phone number to call, and which directory tells you the truth about who's in network. Get it wrong and every subsequent step is wrong too — which is why this is the first thing to check after a move.
The short version
- TRICARE East — run by Humana Military, 800-444-5445. 23 states plus the District of Columbia.
- TRICARE West — run by TriWest Healthcare Alliance, 888-TRIWEST (888-874-9378). 23 states.
- Four states are split by ZIP code — Arkansas, Indiana, Missouri and Wisconsin. Nobody can tell you your region from your state alone.
- Overseas is its own region, run by International SOS Government Services.
What changed on January 1, 2025 — and why it still catches people
Two things happened at once, which is what makes this so confusing. First, six states moved from the East Region to the West Region: Arkansas, Illinois, Louisiana, Oklahoma, Texas and Wisconsin. Second, the West Region changed contractors entirely — TriWest Healthcare Alliance replaced Health Net Federal Services.
So a family in Texas who had spent years dealing with Humana Military woke up on January 1, 2025 with a different region, a different company, a different phone number and a different provider network. If your referrals or your pharmacy went sideways around then, that's why. And if you're reading an older article or a printout from your last duty station, assume it's wrong.
A detail worth knowing: the 2025 announcement described Arkansas and Wisconsin as moving to the West. TRICARE's current region page instead treats both as ZIP-split states, alongside Indiana and Missouri. We follow the current page — but if you're in either state, that's all the more reason to check your ZIP rather than trust any list, including this one.
The current state-by-state list
Verified against tricare.mil's region page on August 1, 2026.
TRICARE West — TriWest Healthcare Alliance
Alaska, Arizona, California, Colorado, Hawaii, Idaho, Illinois, Iowa, Kansas, Louisiana, Minnesota, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Texas, Utah, Washington, Wyoming.
TRICARE East — Humana Military
Alabama, Connecticut, Delaware, District of Columbia, Florida, Georgia, Kentucky, Maine, Maryland, Massachusetts, Michigan, Mississippi, New Hampshire, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Vermont, Virginia, West Virginia.
Split by ZIP code — could be either
Arkansas, Indiana, Missouri, Wisconsin. TRICARE assigns these ZIP code by ZIP code. Two families in the same state — sometimes in neighbouring towns — can be in different regions with different contractors. Check your ZIP.
What your region actually controls
| TRICARE East | TRICARE West | |
|---|---|---|
| Contractor | Humana Military | TriWest Healthcare Alliance |
| Phone | 800-444-5445 | 888-TRIWEST (888-874-9378) |
| Provider directory | Search East | Search West |
| Non-network directory | East non-network | West non-network |
| Who processes referrals and authorizations | Humana Military | TriWest Healthcare Alliance |
| Who processes claims | Humana Military | TriWest Healthcare Alliance |
Note what is not on that list: your plan, your costs and your covered benefits are set by TRICARE and don't change with region. A Prime enrollee in Georgia and a Prime enrollee in Oregon have the same benefit — they just deal with different companies to use it.
What to do when you PCS across the region line
Moving between regions is the one time this really bites, and the order of operations matters.
- Update your address in DEERS first. Nothing else works until the Defense Enrollment Eligibility Reporting System knows where you live — region assignment follows your address, and your new contractor can't see you until it updates.
- Transfer your enrollment. If you're on Prime, this isn't automatic. Moving without transferring can drop you to a lower level of coverage in the new region.
- Get a new primary care manager assigned in the new region if you're on Prime.
- Re-check any open referrals. A referral approved by Humana Military doesn't carry over to TriWest, and vice versa. Ongoing specialty care is where families get caught.
- Re-check your pharmacy. The pharmacy network is national and run by Express Scripts, so it doesn't change with region — but if your prescriptions were being filled at a military pharmacy, that facility is gone from your life now. See the pharmacy guide.
How to check without guessing
Use TRICARE's own ZIP tool, not a state map. It's authoritative, it's free, and for the four split states it's the only correct answer. Then bookmark your contractor's directory — you'll use it every time you need a new provider.
Related: TRICARE plans explained · Finding a doctor · Military facilities by state
TRICARE benefit rules change on contract cycles and at the turn of each calendar year. This guide was checked against tricare.mil on August 1, 2026. If something here doesn't match what your regional contractor tells you, they're right and we want to know — use the form below.