| MAA | Wellmark |
| MAB | Florida (FL) Blue |
| MAC | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MAD | Premera BCBS of Alaska (AK) |
| MAE | Anthem BCBS of Indiana (IN) |
| MAF | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MAG | BCBS of New Mexico (NM) |
| MAH | Anthem BCBS of Virginia (VA) |
| MAI | Wellmark |
| MAJ | Unassigned Prefix |
| MAK | Anthem BCBS of Kentucky (KY) |
| MAL | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MAM | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MAN | Anthem BCBS of Maine (ME) |
| MAO | Florida (FL) Blue |
| MAP | Anthem BCBS of Colorado (CO) |
| MAQ | Florida (FL) Blue |
| MAR | Anthem BCBS of Georgia (GA) |
| MAS | Anthem BCBS of Georgia (GA) |
| MAT | BCBS of Texas (TX) |
| MAU | Wellmark |
| MAV | Anthem BCBS of Ohio (OH) |
| MAW | Anthem BCBS of Connecticut (CT) |
| MAX | BCBS of Illinois (IL) |
| MAY | BCBS of Nebraska (NE) |
| MAZ | Wellmark |
| MBA | Anthem BCBS of Ohio (OH) |
| MBB | Anthem BCBS of Colorado (CO) |
| MBC | BCBS of Tennessee (TN) |
| MBD | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MBE | BCBS of Nebraska (NE) |
| MBF | Anthem BCBS of Georgia (GA) |
| MBG | BCBS of Alabama (AL) |
| MBH | BCBS of Alabama (AL) |
| MBI | BCBS Blue Care Network Michigan (MI) |
| MBJ | Regence BCBS |
| MBK | Empire BCBS of New York (NY) |
| MBL BCBS Prefix | Anthem Blue Cross(BC) of California (CA) |
| MBM | BCBS of Illinois (IL) |
| MBN | BCBS Blue Care Network Michigan (MI) |
| MBO | Florida (FL) Blue |
| MBP | Anthem BCBS of Indiana (IN) |
| MBQ | Unassigned Prefix |
| MBR | Anthem Blue Cross(BC) of California (CA) |
| MBS | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MBT | Anthem BCBS of Missouri (MO) |
| MBU | BCBS of Massachusetts (MA) |
| MBV | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MBW | Anthem BCBS of Ohio (OH) |
| MBX | BCBS of South Carolina (SC) / Southcarolinablues |
| MBY | BCBS of South Carolina (SC) / Southcarolinablues |
| MBZ | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MCA | Blue shield(BS) of California (CA) |
| MCB | BCBS of Kansas City |
| MCC | BCBS of Texas (TX) |
| MCD | BCBS of Illinois (IL) |
| MCE | Premera BCBS of Alaska (AK) |
| MCF | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MCG | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MCH | Florida (FL) Blue |
| MCI | Anthem BCBS of Georgia (GA) |
| MCJ | Highmark BCBS of Western Virginia (WV) |
| MCK | Wellmark |
| MCL | Wellmark |
| MCM | Arkansas (AR) Blue Cross |
| MCN | Wellmark |
| MCO BCBS Prefix | Anthem BCBS of Virginia (VA) |
| MCP | Unassigned Prefix |
| MCQ | BCBS of Illinois (IL) |
| MCR | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MCS | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MCT | Wellmark |
| MCU | BCBS of North Carolina (NC) |
| MCV | Wellmark |
| MCW | Wellmark |
| MCX | BCBS of Massachusetts (MA) |
| MCY | Anthem BCBS of Virginia (VA) |
| MCZ | Anthem BCBS of Indiana (IN) |
| MDA | BCBS Blue Care Network Michigan (MI) |
| MDB | BCBS of South Carolina (SC) / Southcarolinablues |
| MDC BCBS Prefix | BCBS of Minnesota (MN) |
| MDD | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MDE | Anthem Blue Cross(BC) of California (CA) |
| MDF | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MDG | BCBS Blue Care Network Michigan (MI) |
| MDH | BCBS of Rhode Island (RI) |
| MDI | Wellmark |
| MDJ | Anthem BCBS of Indiana (IN) |
| MDK | BCBS of North Carolina (NC) |
| MDL | Unassigned Prefix |
| MDM | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MDN | Anthem BCBS of Wisconsin (WI) |
| MDO | Unassigned Prefix |
| MDP | Blue shield(BS) of California (CA) |
| MDQ | BCBS of Minnesota (MN) |
| MDR | Anthem BCBS of Wisconsin (WI) |
| MDS | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MDT | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MDU | Wellmark |
| MDV | BCBS of Louisiana(LA) |
| MDW | Wellmark |
| MDX | BCBS of Illinois (IL) |
| MDY | BCBS of Kansas City |
| MDZ | BCBS of Minnesota (MN) |
| MEA | Blue shield(BS) of California (CA) |
| MEB | Anthem BCBS of Maine (ME) |
| MEC | Anthem BCBS of Virginia (VA) |
| MED | Anthem BCBS of Indiana (IN) |
| MEE | Anthem BCBS of Virginia (VA) |
| MEF | Unassigned Prefix |
| MEG | Anthem BCBS of Georgia (GA) |
| MEH | Unassigned Prefix |
| MEI | BCBS Blue Care Network Michigan (MI) |
| MEJ | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MEK | Blue shield(BS) of California (CA) |
| MEL | Wellmark |
| MEM | Wellmark |
| MEN | Anthem BCBS of Maine (ME) |
| MEO | Blue shield(BS) of California (CA) |
| MEP | Anthem BCBS of Maine (ME) |
| MEQ | Blue shield(BS) of California (CA) |
| MER | Unassigned Prefix |
| MES | BCBS of Oklahoma (OK) |
| MET | BCBS of Nebraska (NE) |
| MEU | BCBS of Texas (TX) |
| MEV | Unassigned Prefix |
| MEW | Anthem BCBS of Maine (ME) |
| MEX | BCBS of New Mexico (NM) |
| MEY | Anthem BCBS of Maine (ME) |
| MEZ | BCBS of New Mexico (NM) |
| MFA | BCBS of Illinois (IL) |
| MFB | Wellmark |
| MFC | Anthem BCBS of Georgia (GA) |
| MFD | Anthem BCBS of Georgia (GA) |
| MFE | Anthem Blue Cross(BC) of California (CA) |
| MFF | Regence BCBS |
| MFG | Anthem BCBS of Ohio (OH) |
| MFH | Anthem BCBS of Georgia (GA) |
| MFI | Wellmark |
| MFJ | Unassigned Prefix |
| MFK | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MFL | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MFM | Anthem BCBS of Georgia (GA) |
| MFN | Anthem BCBS of Virginia (VA) |
| MFO | Unassigned Prefix |
| MFP | Regence BCBS |
| MFQ | Anthem BCBS of Virginia (VA) |
| MFR | Unassigned Prefix |
| MFS | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MFT | Unassigned Prefix |
| MFU | Wellmark |
| MFV | BCBS of Illinois (IL) |
| MFW | Anthem Blue Cross(BC) of California (CA) |
| MFX | BCBS Blue Care Network Michigan (MI) |
| MFY | BCBS of Minnesota (MN) |
| MFZ | BCBS of Illinois (IL) |
| MGA | Blue shield(BS) of California (CA) |
| MGB | Capital Blue Cross of Pennsylvania (PA) |
| MGC | BCBS of Illinois (IL) |
| MGD | Premera BCBS of Alaska (AK) |
| MGE | BCBS of Rhode Island (RI) |
| MGF | Unassigned Prefix |
| MGG | Blue shield(BS) of California (CA) |
| MGH | Unassigned Prefix |
| MGI | Highmark BCBS of Pennsylvania (PA) |
| MGJ | Anthem BCBS of Missouri (MO) |
| MGK | Wellmark |
| MGL | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MGM | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MGN | BCBS of South Carolina (SC) / Southcarolinablues |
| MGO | BCBS Blue Care Network Michigan (MI) |
| MGP | Wellmark |
| MGQ | Unassigned Prefix |
| MGR | BCBS Blue Care Network Michigan (MI) |
| MGS | Anthem BCBS of Georgia (GA) |
| MGT | Regence BCBS |
| MGU | Anthem BCBS of Virginia (VA) |
| MGV | BCBS of South Carolina (SC) / Southcarolinablues |
| MGW | Arkansas (AR) Blue Cross |
| MGX | Unassigned Prefix |
| MGY | Blue shield(BS) of California (CA) |
| MGZ | Horizon BCBS of New Jersey (NJ) |
| MHA | BCBS of Kansas City |
| MHB | BCBS of Texas (TX) |
| MHC | Highmark BCBS of Pennsylvania (PA) |
| MHD | Unassigned Prefix |
| MHE | Unassigned Prefix |
| MHF | Unassigned Prefix |
| MHG | Anthem Blue Cross(BC) of California (CA) |
| MHH | BCBS Blue Care Network Michigan (MI) |
| MHI | Anthem BCBS of Georgia (GA) |
| MHJ | Unassigned Prefix |
| MHK | Wellmark |
| MHL | Unassigned Prefix |
| MHM | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MHN | Anthem BCBS of Ohio (OH) |
| MHO | Unassigned Prefix |
| MHP | Empire BCBS of New York (NY) |
| MHQ | Anthem BCBS of Georgia (GA) |
| MHR | Anthem BCBS of Ohio (OH) |
| MHS | Anthem BCBS of Kentucky (KY) |
| MHT | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MHU | Unassigned Prefix |
| MHV | Unassigned Prefix |
| MHW | BCBS of Alabama (AL) |
| MHX | Unassigned Prefix |
| MHY | Anthem Blue Cross(BC) of California (CA) |
| MHZ | Wellmark |
| MIA | Blue shield(BS) of California (CA) |
| MIB | BCBS of Minnesota (MN) |
| MIC | BCBS of South Carolina (SC) / Southcarolinablues |
| MID | Unassigned Prefix |
| MIE | BCBS of Minnesota (MN) |
| MIF | Anthem BCBS of Ohio (OH) |
| MIG | BCBS Blue Care Network Michigan (MI) |
| MIH | Unassigned Prefix |
| MII | BCBS of Kansas City |
| MIJ | BCBS Blue Care Network Michigan (MI) |
| MIK | Unassigned Prefix |
| MIL | BCBS of Massachusetts (MA) |
| MIM | Highmark BCBS of Pennsylvania (PA) |
| MIN | Premera BCBS of Alaska (AK) |
| MIO | Blue shield(BS) of California (CA) |
| MIP | Blue Cross (BC) of Idaho (ID) |
| MIQ | Anthem BCBS of Ohio (OH) |
| MIR | Unassigned Prefix |
| MIS | Anthem BCBS of Ohio (OH) |
| MIT | Wellmark |
| MIU | BCBS of South Carolina (SC) / Southcarolinablues |
| MIV | BCBS of Western New York (WNY) |
| MIW | BCBS Blue Care Network Michigan (MI) |
| MIX | Blue shield(BS) of California (CA) |
| MIY | Unassigned Prefix |
| MIZ | Blue shield(BS) of California (CA) |
| MJA | Unassigned Prefix |
| MJB | Anthem BCBS of Colorado (CO) |
| MJC | BCBS of Texas (TX) |
| MJD | BCBS of Alabama (AL) |
| MJE | BCBS Blue Care Network Michigan (MI) |
| MJF | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MJG | Premera BCBS of Alaska (AK) |
| MJH | Anthem BCBS of Wisconsin (WI) |
| MJI | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MJJ | BCBS Blue Care Network Michigan (MI) |
| MJK | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MJL | Anthem Blue Cross(BC) of California (CA) |
| MJM | Highmark BCBS of Pennsylvania (PA) |
| MJN | Highmark BCBS of Pennsylvania (PA) |
| MJO | Anthem BCBS of Connecticut (CT) |
| MJP | Wellmark |
| MJQ | Anthem Blue Cross(BC) of California (CA) |
| MJR | BCBS Blue Care Network Michigan (MI) |
| MJS | BCBS of Tennessee (TN) |
| MJT | Anthem BCBS of Wisconsin (WI) |
| MJU | BCBS Blue Care Network Michigan (MI) |
| MJV | Anthem BCBS of Wisconsin (WI) |
| MJW | Unassigned Prefix |
| MJX | BCBS Blue Care Network Michigan (MI) |
| MJY | Unassigned Prefix |
| MJZ | Unassigned Prefix |
| MKA | Wellmark |
| MKB | Blue shield(BS) of California (CA) |
| MKC | BCBS of South Carolina (SC) / Southcarolinablues |
| MKD | BCBS of Massachusetts (MA) |
| MKE | BCBS of Tennessee (TN) |
| MKF | Unassigned Prefix |
| MKG | Anthem BCBS of Ohio (OH) |
| MKH | BCBS of Tennessee (TN) |
| MKI | BCBS of Tennessee (TN) |
| MKJ | Anthem BCBS of Ohio (OH) |
| MKK | Anthem Blue Cross(BC) of California (CA) |
| MKL | BCBS of Mississippi (MS) |
| MKM | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MKN | Unassigned Prefix |
| MKO | BCBS Blue Care Network Michigan (MI) |
| MKP | BCBS Blue Care Network Michigan (MI) |
| MKQ | Unassigned Prefix |
| MKR | BCBS of Illinois (IL) |
| MKS | BCBS of Massachusetts (MA) |
| MKT | Wellmark |
| MKU | Premera BCBS of Alaska (AK) |
| MKV | Horizon BCBS of New Jersey (NJ) |
| MKW | Wellmark |
| MKX | Unassigned Prefix |
| MKY | Horizon BCBS of New Jersey (NJ) |
| MKZ | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MLA | Wellmark |
| MLB | Unassigned Prefix |
| MLC | Unassigned Prefix |
| MLD | Unassigned Prefix |
| MLE | BCBS of Illinois (IL) |
| MLF | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MLG | Highmark BCBS of Pennsylvania (PA) |
| MLH | BCBS of South Carolina (SC) / Southcarolinablues |
| MLI | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MLJ | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MLK | Anthem BCBS of Virginia (VA) |
| MLL | Blue shield(BS) of California (CA) |
| MLM | Highmark BCBS of Pennsylvania (PA) |
| MLN | Blue shield(BS) of California (CA) |
| MLO | BCBS of Western New York (WNY) |
| MLP | Anthem BCBS of Virginia (VA) |
| MLQ | BCBS of Minnesota (MN) |
| MLR | BCBS of Massachusetts (MA) |
| MLS | Unassigned Prefix |
| MLT | BCBS of Nebraska (NE) |
| MLU | BCBS of Minnesota (MN) |
| MLV | BCBS of Minnesota (MN) |
| MLW | Unassigned Prefix |
| MLX | Blue Cross (BC) of Idaho (ID) |
| MLY | Premera BCBS of Alaska (AK) |
| MLZ | BCBS of Rhode Island (RI) |
| MMA | Empire BCBS of New York (NY) |
| MMB | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MMC | Anthem BCBS of Georgia (GA) |
| MMD | Premera BCBS of Alaska (AK) |
| MME | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MMF | Excellus BCBS of New York (NY) |
| MMG | BCBS of Mississippi (MS) |
| MMH | Empire BCBS of New York (NY) |
| MMI | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MMJ | BCBS Blue Care Network Michigan (MI) |
| MMK | BCBS of Illinois (IL) |
| MML | BCBS of Illinois (IL) |
| MMM | BCBS of Minnesota (MN) |
| MMN | BCBS of Minnesota (MN) |
| MMO | BCBS Blue Care Network Michigan (MI) |
| MMP | Anthem BCBS of Georgia (GA) |
| MMQ | Anthem BCBS of Indiana (IN) |
| MMR | BCBS of Massachusetts (MA) |
| MMS | Anthem BCBS of Ohio (OH) |
| MMT | Blue shield(BS) of California (CA) |
| MMU | BCBS of Illinois (IL) |
| MMV | Anthem BCBS of Ohio (OH) |
| MMW | BCBS of Illinois (IL) |
| MMX | BCBS of Alabama (AL) |
| MMY | Anthem BCBS of Indiana (IN) |
| MMZ | Wellmark |
| MNA | BCBS of Minnesota (MN) |
| MNB | BCBS of Massachusetts (MA) |
| MNC | Anthem Blue Cross(BC) of California (CA) |
| MND | Anthem BCBS of Wisconsin (WI) |
| MNE | Anthem BCBS of Wisconsin (WI) |
| MNF | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MNG | BCBS of Tennessee (TN) |
| MNH | Anthem BCBS of Virginia (VA) |
| MNI | Unassigned Prefix |
| MNJ | Anthem BCBS of Ohio (OH) |
| MNK | Anthem BCBS of Ohio (OH) |
| MNL | Unassigned Prefix |
| MNM | Unassigned Prefix |
| MNN | Highmark BCBS of Pennsylvania (PA) |
| MNO | Unassigned Prefix |
| MNP | Blue shield(BS) of California (CA) |
| MNQ | BCBS of Minnesota (MN) |
| MNR | BCBS of Minnesota (MN) |
| MNS | Anthem BCBS of Kentucky (KY) |
| MNT | BCBS of Illinois (IL) |
| MNU | BCBS of North Carolina (NC) |
| MNV | BCBS of South Carolina (SC) / Southcarolinablues |
| MNW | Premera BCBS of Alaska (AK) |
| MNX | BCBS of Illinois (IL) |
| MNY | Premera Blue Cross (BC) of Alaska (AK) |
| MNZ | Wellmark |
| MOA | Unassigned Prefix |
| MOB | Unassigned Prefix |
| MOC | Anthem BCBS of Georgia (GA) |
| MOD | BCBS of Massachusetts (MA) |
| MOE | BCBS of Illinois (IL) |
| MOF | Blue shield(BS) of California (CA) |
| MOG | BCBS of Western New York (WNY) |
| MOH | Unassigned Prefix |
| MOI | BCBS of Massachusetts (MA) |
| MOJ | Anthem BCBS of Ohio (OH) |
| MOK | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MOL | Unassigned Prefix |
| MOM | Unassigned Prefix |
| MON | Unassigned Prefix |
| MOO | Unassigned Prefix |
| MOP | Unassigned Prefix |
| MOQ | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MOR | Premera BCBS of Alaska (AK) |
| MOS | Blue shield(BS) of California (CA) |
| MOT | Unassigned Prefix |
| MOU | BCBS Blue Care Network Michigan (MI) |
| MOV | Arkansas (AR) Blue Cross |
| MOW | Anthem BCBS of Kentucky (KY) |
| MOX | Unassigned Prefix |
| MOY | Wellmark |
| MOZ | Unassigned Prefix |
| MPA | Anthem BCBS of Ohio (OH) |
| MPB | Anthem BCBS of Georgia (GA) |
| MPC | BCBS of Rhode Island (RI) |
| MPD | BCBS of Texas (TX) |
| MPE | BCBS Blue Care Network Michigan (MI) |
| MPF | Excellus BCBS of New York (NY) |
| MPG | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MPH | Empire BCBS of New York (NY) |
| MPI BCBS Prefix | Anthem Blue Cross(BC) of California (CA) |
| MPJ | BCBS of South Carolina (SC) / Southcarolinablues |
| MPK | Unassigned Prefix |
| MPL | BCBS of Illinois (IL) |
| MPM | Blue shield(BS) of Northeastern New York (NeNY) |
| MPN | Wellmark |
| MPO | BCBS of Alabama (AL) |
| MPP | Anthem BCBS of Wisconsin (WI) |
| MPQ | BCBS of Minnesota (MN) |
| MPR | Anthem Blue Cross(BC) of California (CA) |
| MPS | Anthem BCBS of Georgia (GA) |
| MPT | BCBS of Minnesota (MN) |
| MPU | Anthem BCBS of Ohio (OH) |
| MPV | Anthem BCBS of Georgia (GA) |
| MPW | Anthem BCBS of Ohio (OH) |
| MPX | BCBS of Minnesota (MN) |
| MPY | Florida (FL) Blue |
| MPZ | Unassigned Prefix |
| MQA | BCBS Blue Care Network Michigan (MI) |
| MQB | Unassigned Prefix |
| MQC | Unassigned Prefix |
| MQD | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MQE | Anthem BCBS of Georgia (GA) |
| MQF | Unassigned Prefix |
| MQG | Unassigned Prefix |
| MQH | BCBS Blue Care Network Michigan (MI) |
| MQI | Wellmark |
| MQJ | BCBS Blue Care Network Michigan (MI) |
| MQK | BCBS Blue Care Network Michigan (MI) |
| MQL | BCBS Blue Care Network Michigan (MI) |
| MQM | Unassigned Prefix |
| MQN | Unassigned Prefix |
| MQO | BCBS Blue Care Network Michigan (MI) |
| MQP | Unassigned Prefix |
| MQQ | Blue Cross (BC) of Idaho (ID) |
| MQR | Highmark BCBS of Pennsylvania (PA) |
| MQS | Unassigned Prefix |
| MQT | Unassigned Prefix |
| MQU | Anthem BCBS of Wisconsin (WI) |
| MQV | BCBS of Nebraska (NE) |
| MQW | BCBS Blue Care Network Michigan (MI) |
| MQX | Anthem Blue Cross(BC) of California (CA) |
| MQY | Unassigned Prefix |
| MQZ | Anthem Blue Cross(BC) of California (CA) |
| MRA | Unassigned Prefix |
| MRB | Unassigned Prefix |
| MRC | BCBS of Illinois (IL) |
| MRD | Unassigned Prefix |
| MRE | Wellmark |
| MRF | BCBS Blue Care Network Michigan (MI) |
| MRG | BCBS of Illinois (IL) |
| MRH | Anthem BCBS of Wisconsin (WI) |
| MRI | Unassigned Prefix |
| MRJ | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MRK | BCBS of Massachusetts (MA) |
| MRL | Wellmark |
| MRM | BCBS of Kansas City |
| MRN | Anthem BCBS of Wisconsin (WI) |
| MRO | Unassigned Prefix |
| MRP | Anthem BCBS of Wisconsin (WI) |
| MRQ | Anthem BCBS of Ohio (OH) |
| MRR | BCBS of Minnesota (MN) |
| MRS | Wellmark |
| MRT | BCBS of Texas (TX) |
| MRU | Highmark BCBS of Pennsylvania (PA) |
| MRV | Anthem Blue Cross(BC) of California (CA) |
| MRW | BCBS of Illinois (IL) |
| MRX | Anthem BCBS of Wisconsin (WI) |
| MRY | BCBS of Alabama (AL) |
| MRZ | BCBS of Illinois (IL) |
| MSA | BCBS of Alabama (AL) |
| MSB | Wellmark |
| MSC | BCBS of Alabama (AL) |
| MSD | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MSE | BCBS Blue Care Network Michigan (MI) |
| MSF | Empire BCBS of New York (NY) |
| MSG | BCBS Blue Care Network Michigan (MI) |
| MSH | BCBS Blue Care Network Michigan (MI) |
| MSI | Regence BCBS |
| MSJ BCBS Prefix | Premera BCBS of Alaska (AK) |
| MSK | BCBS of Massachusetts (MA) |
| MSL | Unassigned Prefix |
| MSM | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MSN | Anthem BCBS of Ohio (OH) |
| MSO | Unassigned Prefix |
| MSP | Premera BCBS of Alaska (AK) |
| MSQ | Premera BCBS of Alaska (AK) |
| MSR | BCBS Blue Care Network Michigan (MI) |
| MSS | Anthem BCBS of Virginia (VA) |
| MST | Premera BCBS of Alaska (AK) |
| MSU | Anthem BCBS of Ohio (OH) |
| MSV | BCBS of Alabama (AL) |
| MSW | BCBS of Illinois (IL) |
| MSX | Unassigned Prefix |
| MSY | BCBS of North Carolina (NC) |
| MSZ | Anthem Blue Cross(BC) of California (CA) |
| MTA | Anthem BCBS of Virginia (VA) |
| MTB | Wellmark |
| MTC | Anthem BCBS of Virginia (VA) |
| MTD | Premera BCBS of Alaska (AK) |
| MTE | Blue Shield (BS) of California |
| MTF | Anthem BCBS of Georgia (GA) |
| MTG | Unassigned Prefix |
| MTH | Wellmark |
| MTI | Blue shield(BS) of California (CA) |
| MTJ | Unassigned Prefix |
| MTK | Unassigned Prefix |
| MTL | Unassigned Prefix |
| MTM | Unassigned Prefix |
| MTN BCBS Prefix | BCBS of Massachusetts (MA) |
| MTO | Blue Shield (BS) of California |
| MTP | BCBS of Massachusetts (MA) |
| MTQ | Unassigned Prefix |
| MTR | BCBS of Tennessee (TN) |
| MTS | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MTT | Blue Shield (BS) of California |
| MTU | Premera Blue Cross (BC) of Alaska (AK) |
| MTV | Anthem BCBS of Indiana (IN) |
| MTW | Anthem BCBS of Ohio (OH) |
| MTX | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MTY | Anthem Blue Cross(BC) of California (CA) |
| MTZ | BCBS of Illinois (IL) |
| MUA | BCBS of Texas (TX) |
| MUB | Anthem BCBS of Virginia (VA) |
| MUC | Wellmark |
| MUD | Wellmark |
| MUE | Wellmark |
| MUF | Anthem BCBS of Wisconsin (WI) |
| MUG | Arkansas (AR) Blue Cross |
| MUH | Blue Cross (BC) of Idaho (ID) |
| MUI | Unassigned Prefix |
| MUJ | Anthem BCBS of Indiana (IN) |
| MUK | Anthem BCBS of Wisconsin (WI) |
| MUL | Unassigned Prefix |
| MUM | BCBS of Arizona (AZ) |
| MUN | BCBS of Illinois (IL) |
| MUO | Anthem BCBS of Wisconsin (WI) |
| MUP | BCBS of South Carolina (SC) / Southcarolinablues |
| MUQ | Premera Blue Cross (BC) of Alaska (AK) |
| MUR | BCBS Blue Care Network Michigan (MI) |
| MUS | BCBS of Illinois (IL) |
| MUT | BCBS of Minnesota (MN) |
| MUU | Unassigned Prefix |
| MUV | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MUW | Highmark BCBS of Pennsylvania (PA) |
| MUX | Wellmark |
| MUY | BCBS of Alabama (AL) |
| MUZ | BCBS Blue Care Network Michigan (MI) |
| MVA | BCBS of Montana (MT) |
| MVB | BCBS of Vermont (VT) |
| MVC | Unassigned Prefix |
| MVD | Premera BCBS of Alaska (AK) |
| MVE | BCBS of Massachusetts (MA) |
| MVF | Empire BCBS of New York (NY) |
| MVG | BCBS of Minnesota (MN) |
| MVH | Wellmark |
| MVI | Unassigned Prefix |
| MVJ | Blue Shield (BS) of California |
| MVK | Anthem BCBS of Georgia (GA) |
| MVL | BCBS of Massachusetts (MA) |
| MVM | BCBS of Alabama (AL) |
| MVN | Empire BCBS of New York (NY) |
| MVO | Blue Cross (BC) of Idaho (ID) |
| MVP | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MVQ | Blue Cross (BC) of Idaho (ID) |
| MVR | Highmark BCBS of Pennsylvania (PA) |
| MVS | Unassigned Prefix |
| MVT | BCBS of Minnesota (MN) |
| MVU | Anthem BCBS of Indiana (IN) |
| MVV | Wellmark |
| MVW | Unassigned Prefix |
| MVX | BCBS of South Carolina (SC) / Southcarolinablues |
| MVY | Anthem BCBS of Ohio (OH) |
| MVZ | BCBS of Texas (TX) |
| MWA | BCBS of Illinois (IL) |
| MWB | Unassigned Prefix |
| MWC | Unassigned Prefix |
| MWD | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MWE | Anthem BCBS of Wisconsin (WI) |
| MWF | BCBS of Illinois (IL) |
| MWG | BCBS of Minnesota (MN) |
| MWH | BCBS of Illinois (IL) |
| MWI | Unassigned Prefix |
| MWJ | Horizon BCBS of New Jersey (NJ) |
| MWK | Horizon BCBS of New Jersey (NJ) |
| MWL | BCBS of Illinois (IL) |
| MWM | Anthem BCBS of Wisconsin (WI) |
| MWN | BCBS of Illinois (IL) |
| MWO | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MWP | BCBS of Massachusetts (MA) |
| MWQ | Unassigned Prefix |
| MWR | BCBS of Kansas City |
| MWS | Unassigned Prefix |
| MWT | Unassigned Prefix |
| MWU | Anthem BCBS of Wisconsin (WI) |
| MWV | Anthem BCBS of Wisconsin (WI) |
| MWW | Anthem BCBS of Nevada (NV) |
| MWX | BCBS of Alabama (AL) |
| MWY | Unassigned Prefix |
| MWZ | Independence Blue Cross(BC) of Philadelphia(Phi) and Southeastern Pennsylvania(PA) |
| MXA | Anthem Blue Cross(BC) of California (CA) |
| MXB | Unassigned Prefix |
| MXC | Unassigned Prefix |
| MXD | BCBS of Texas (TX) |
| MXE | BCBS of Texas (TX) |
| MXF | Empire BCBS of New York (NY) |
| MXG | Unassigned Prefix |
| MXH BCBS Prefix | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MXI | Blue Shield (BS) of California |
| MXJ | Unassigned Prefix |
| MXK | Capital Blue Cross of Pennsylvania (PA) |
| MXL | Wellmark |
| MXM | Wellmark |
| MXN | BCBS of Massachusetts (MA) |
| MXO | Wellmark |
| MXP | BCBS of Massachusetts (MA) |
| MXQ | Empire BCBS of New York (NY) |
| MXR | Anthem Blue Cross(BC) of California (CA) |
| MXS | Anthem BCBS of Georgia (GA) |
| MXT | Unassigned Prefix |
| MXU | Anthem BCBS of Connecticut (CT) |
| MXV | Blue Cross (BC) of Idaho (ID) |
| MXW | Blue Cross (BC) of Idaho (ID) |
| MXX | Unassigned Prefix |
| MXY | BCBS of Massachusetts (MA) |
| MXZ | Premera BCBS of Alaska (AK) |
| MYA | Unassigned Prefix |
| MYB | Regence BCBS |
| MYC | Unassigned Prefix |
| MYD | BCBS of Massachusetts (MA) |
| MYE | Anthem BCBS of Ohio (OH) |
| MYF | Empire BCBS of New York (NY) |
| MYG | Wellmark |
| MYH | BCBS of Massachusetts (MA) |
| MYI | BCBS of Massachusetts (MA) |
| MYJ | Unassigned Prefix |
| MYK | BCBS of Massachusetts (MA) |
| MYL | BCBS of Massachusetts (MA) |
| MYM | Anthem BCBS of Ohio (OH) |
| MYN | Anthem BCBS of Ohio (OH) |
| MYO | Unassigned Prefix |
| MYP | Unassigned Prefix |
| MYQ | BCBS of Massachusetts (MA) |
| MYR | BCBS of Alabama (AL) |
| MYS | BCBS of Massachusetts (MA) |
| MYT | BCBS Blue Care Network Michigan (MI) |
| MYU | BCBS of Massachusetts (MA) |
| MYV | Unassigned Prefix |
| MYW | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MYX | BCBS of Oklahoma (OK) |
| MYY BCBS Prefix | Carefirst BCBS of Maryland (MD)/ District of Columbia (DC) and Northern Virginia (VA) |
| MYZ | BCBS of Massachusetts (MA) |
| MZA | Wellmark |
| MZB | Highmark BCBS of Pennsylvania (PA) |
| MZC | BCBS of Rhode Island (RI) |
| MZD | BCBS of Illinois (IL) |
| MZE | BCBS of Massachusetts (MA) |
| MZF | Unassigned Prefix |
| MZG | BCBS of Illinois (IL) |
| MZH | BCBS of Arizona (AZ) |
| MZI | Blue Shield (BS) of California |
| MZJ | Anthem BCBS of Wisconsin (WI) |
| MZK | Anthem BCBS of Virginia (VA) |
| MZL | BCBS of Alabama (AL) |
| MZM | BCBS of Minnesota (MN) |
| MZN | BCBS of North Carolina (NC) |
| MZO | BCBS Blue Care Network Michigan (MI) |
| MZP | BCBS Blue Care Network Michigan (MI) |
| MZQ | BCBS of Minnesota (MN) |
| MZR | BCBS of Minnesota (MN) |
| MZS | Unassigned Prefix |
| MZT | BCBS of Minnesota (MN) |
| MZU | Florida (FL) Blue |
| MZV | Unassigned Prefix |
| MZW | BCBS of Minnesota (MN) |
| MZX | BCBS of Minnesota (MN) |
| MZY | BCBS Blue Care Network Michigan (MI) |
| MZZ | BCBS of Minnesota (MN) |
