BCBS prefix lookup: which Blue plan a member ID belongs to
By Javier Alvarez · Updated · 3 min read
| Prefixes | 17, each named in its home plan's own 2026 document |
|---|---|
| Plans | Blue Cross and Blue Shield of Illinois |
| Each prefix | Home plan, network, area, where to file, how to verify, MNT policy |
| Format | This lookup, a page per prefix, and a free PDF |
How to read a Blue Cross Blue Shield member ID
The first three characters of a Blue Cross Blue Shield member ID are the prefix. It identifies the member's home plan, the Blue company that holds the coverage, and BlueCard uses it to route eligibility checks and claims there (BCBS of Texas). The full ID is the prefix plus everything after it, up to 17 characters, and it must go on the claim exactly as printed (BCBS of Illinois).
You still file with your local Blue plan, the one you're contracted with; it forwards the claim to the home plan. To check benefits, use your local plan's eligibility tools or call BlueCard Eligibility at 1-800-676-BLUE (2583). Medicare Advantage and Medicaid members have their own out-of-area rules, so for those prefixes ask your local Blue plan first.
Every prefix in the lookup
The Blue Cross Blue Shield Association doesn't publish a list of every prefix, and lookup sites copy each other's guesses. We only add a prefix when the home plan's own document names it. Today that is Blue Cross and Blue Shield of Illinois's 2026 network documents, 17 prefixes, each with its own page:
| Prefix | Home plan | Plan type | Network | Who it covers |
|---|---|---|---|---|
| BLN | BCBS of Illinois | Commercial | MyBlue Plus POS | Individuals, through the state and federal Marketplaces |
| CTY | BCBS of Illinois | Commercial | Blue Choice OPT PPO, Tier 1 and Tier 2 | The City of Chicago |
| JLX | BCBS of Illinois | Medicare Advantage | Medicare Advantage Group PPO | Group Medicare Advantage for named employer groups only |
| QMC | BCBS of Illinois | Commercial HMO | BlueCare Direct (with Advocate) | Individuals, off the Marketplace, through BCBS of Illinois |
| QMD | BCBS of Illinois | Commercial HMO | BlueCare Direct (with Advocate) | Individuals, on the Marketplace public exchange |
| QME | BCBS of Illinois | Commercial | Blue Choice Preferred PPO | Individuals, off the Marketplace, through BCBS of Illinois |
| QMF | BCBS of Illinois | Commercial | Blue Choice Preferred PPO | Individuals, on the Marketplace public exchange |
| QMG | BCBS of Illinois | Commercial | Blue Choice Preferred PPO | Small groups, off the Marketplace, through BCBS of Illinois |
| XOD | BCBS of Illinois | Medicare Advantage | Medicare Advantage PPO | Medicare Advantage |
| XOF | BCBS of Illinois | Commercial | PPO | Not stated |
| XOH | BCBS of Illinois | Commercial HMO | HMO Illinois, Blue Advantage HMO, and Blue Precision HMO for small groups | HMO Illinois and Blue Advantage HMO members, and Blue Precision HMO small groups off the Marketplace |
| XOJ | BCBS of Illinois | Medicare Advantage | Medicare Advantage HMO, and Blue Medicare Advocate Health | Medicare Advantage |
| XOL | BCBS of Illinois | Commercial HMO | Blue Precision HMO | Individuals, on the Marketplace public exchange |
| XOO | BCBS of Illinois | Commercial HMO | Blue Precision HMO | Individuals, off the Marketplace, through BCBS of Illinois |
| XOU | BCBS of Illinois | Commercial | Blue Choice PPO | Not stated |
| XOX | BCBS of Illinois | Commercial | Blue Choice OPT PPO, Tier 1 and Tier 2 | Not stated |
| XXL | BCBS of Illinois | Medicaid | Blue Cross Community Health Plans | Illinois Medicaid managed care, including the MLTSS population |
A prefix that isn't here may still be valid: the plan's lists are not exhaustive, and plans add prefixes as they need them. Ask your local Blue plan or BlueCard Eligibility which plan it belongs to.
Where the facts come from
From Blue Cross and Blue Shield of Illinois's own 2026 network documents and provider policies, opened October 30, 2026. For which MNT codes each payer's policy lists, see MNT coverage by payer. If you'd rather not file Blue claims yourself, Duo Practice files them for you for 3.9% of what is collected; see the billing service.