| M2A | Unassigned Prefix |
| M2B | Unassigned Prefix |
| M2C | Blue Cross Blue Shield of Illinois |
| M2D | Blue Cross Blue Shield of Illinois |
| M2E | Blue Cross Blue Shield of Texas |
| M2F | Blue Cross Blue Shield of Texas |
| M2G | Blue Cross Blue Shield of Texas |
| M2H | Regence Blue Cross Blue Shield |
| M2I | Blue Cross Blue Shield of Western New York |
| M2J | Blue Cross Blue Shield of Illinois |
| M2K | Blue Cross Blue Shield of Arizona |
| M2L | Blue Cross of Massachusetts |
| M2M | Anthem Blue Cross of California |
| M2N | Anthem Blue Cross Blue Shield of Wisconsin |
| M2O | Unassigned Prefix |
| M2P | Regence Blue Cross Blue Shield |
| M2Q | Anthem Blue Cross Blue Shield of Wisconsin |
| M2R | Blue Cross Blue Shield of Texas |
| M2S | Blue Cross Blue Shield of Illinois |
| M2T | Regence Blue Cross Blue Shield |
| M2U | Anthem Blue Cross Blue Shield of Wisconsin |
| M2V | Blue Cross Blue Shield of Arizona |
| M2W | Blue Cross Blue Shield of Rhode Island |
| M2X | Blue Cross Blue Shield of Montana |
| M2Y | Regence Blue Cross Blue Shield |
| M2Z | Anthem Blue Cross Blue Shield of Wisconsin |
| M3A | Blue Cross Blue Shield of Kansas |
| M3B | Blue Cross Blue Shield of Western New York |
| M3C | Blue Cross Blue Shield of Rhode Island |
| M3D | Regence Blue Cross Blue Shield |
| M3E | Blue Cross Blue Shield of Illinois |
| M3F | Blue Cross Blue Shield of Texas |
| M3G | Blue Cross Blue Shield of Rhode Island |
| M3H | Blue Cross Blue Shield of Minnesota |
| M3I | Unassigned Prefix |
| M3J | Empire Blue Cross Blue Shield |
| M3K | Anthem Blue Cross Blue Shield of Wisconsin |
| M3L | Blue Cross Blue Shield of Michigan |
| M3M | Regence Blue Cross Blue Shield |
| M3N | Anthem Blue Cross Blue Shield of Maine |
| M3O | Anthem Blue Cross Blue Shield of Virginia |
| M3P | Blue Cross Blue Shield of Arizona |
| M3Q | Anthem Blue Cross Blue Shield of Ohio |
| M3R | Blue Cross Blue Shield of Texas |
| M3S | Blue Cross Blue Shield of Illinois |
| M3T | Anthem Blue Cross Blue Shield of Georgia |
| M3U | Anthem Blue Cross Blue Shield of Indiana |
| M3V | Blue Cross Blue Shield of Arizona |
| M3W | Regence Blue Cross Blue Shield |
| M3X | Anthem Blue Cross Blue Shield of Wisconsin |
| M3Y | Anthem Blue Cross Blue Shield of Georgia |
| M3Z | Anthem Blue Cross Blue Shield of Georgia |
| M4A | Highmark Blue Cross Blue Shield |
| M4B | Highmark Blue Shield |
| M4C | Anthem Blue Cross Blue Shield of Kentucky |
| M4D | Regence Blue Cross Blue Shield |
| M4E | Blue Cross Blue Shield of Texas |
| M4F | Blue Cross Blue Shield of Texas |
| M4G | Anthem Blue Cross Blue Shield of Virginia |
| M4H | Anthem Blue Cross Blue Shield of Missouri |
| M4I | Unassigned Prefix |
| M4J | Highmark Blue Cross Blue Shield |
| M4K | Blue Cross Blue Shield of Arizona |
| M4L | Highmark Blue Cross Blue Shield |
| M4M | Anthem Blue Cross Blue Shield of Missouri |
| M4N | Anthem Blue Cross Blue Shield of Virginia |
| M4O | Unassigned Prefix |
| M4P | Blue Cross Blue Shield of Texas |
| M4Q | Blue Cross Blue Shield of Michigan |
| M4R | Blue Shield of Northeastern New York |
| M4S | Blue Cross Blue Shield of Illinois |
| M4T | Regence Blue Cross Blue Shield |
| M4U | Blue Cross Blue Shield of Minnesota |
| M4V | Blue Cross Blue Shield of North Dakota |
| M4W | Anthem Blue Cross Blue Shield of Wisconsin |
| M4X | Carefirst Blue Cross Blue Shield |
| M4Y | Blue Cross of Idaho |
| M4Z | Blue Cross Blue Shield of Texas |
| M5A | Blue Cross Blue Shield of Minnesota |
| M5B | Anthem Blue Cross Blue Shield of Ohio |
| M5C | Anthem Blue Cross Blue Shield of Missouri |
| M5D | Anthem Blue Cross Blue Shield of Missouri |
| M5E | Anthem Blue Cross Blue Shield of Missouri |
| M5F | Blue Cross Blue Shield of Texas |
| M5G | Blue Cross Blue Shield of Michigan |
| M5H | Blue Cross Blue Shield of Texas |
| M5I | Anthem Blue Cross of California |
| M5J | Carefirst Blue Cross Blue Shield |
| M5K | Blue Cross Blue Shield of Illinois |
| M5L | Independence Blue Cross |
| M5M | Blue Cross Blue Shield of Texas |
| M5N | Blue Cross of Massachusetts |
| M5O | Unassigned Prefix |
| M5P | Carefirst Blue Cross Blue Shield |
| M5Q | Anthem Blue Cross Blue Shield of Georgia |
| M5R | Blue Cross Blue Shield of Western New York |
| M5S | Blue Cross Blue Shield of Texas |
| M5T | Blue Cross of Massachusetts |
| M5U | Anthem Blue Cross of California |
| M5V | Carefirst Blue Cross Blue Shield |
| M5W | Anthem Blue Cross Blue Shield of Virginia |
| M5X | Blue Cross Blue Shield of Illinois |
| M5Y | Blue Cross Blue Shield of Oklahoma |
| M5Z | Anthem Blue Cross Blue Shield of Colorado |
| M6A | Blue Cross Blue Shield of Texas |
| M6B | Anthem Blue Cross Blue Shield of New Hampshire |
| M6C | Empire Blue Cross Blue Shield |
| M6D | Carefirst Blue Cross Blue Shield |
| M6E | Empire Blue Cross Blue Shield |
| M6F | Blue Cross Blue Sheild of Texas |
| M6G | Empire Blue Cross Blue Shield |
| M6H | Empire Blue Cross Blue Shield |
| M6I | Unassigned Prefix |
| M6J | Anthem Blue Cross Blue Shield of Indiana |
| M6K | Anthem Blue Cross Blue Shield of Virginia |
| M6L | Anthem Blue Cross Blue Shield of Virginia |
| M6M | Anthem Blue Cross Blue Shield of Kentucky |
| M6N | Blue Cross Blue Shield of Minnesota |
| M6O | Anthem Blue Cross Blue Shield of Virginia |
| M6P | Carefirst Blue Cross Blue Shield |
| M6Q | Regence Blue Cross Blue Shield |
| M6R | Carefirst Blue Cross Blue Shield |
| M6S | Blue Cross Blue Shield of Illinois |
| M6T | Carefirst Blue Cross Blue Shield |
| M6U | Anthem Blue Cross Blue Shield of Ohio |
| M6V | Anthem Blue Cross Blue Shield of Nevada |
| M6W | Anthem Blue Cross Blue Shield of Wisconsin |
| M6X | Anthem Blue Cross Blue Shield of Wisconsin |
| M6Y | Empire Blue Cross Blue Shield |
| M6Z | Anthem Blue Cross Blue Shield of Missouri |
| M7A | Anthem Blue Cross of California |
| M7B | Premera Blue Cross Blue Shield of Alaska |
| M7C | Empire Blue Cross Blue Shield |
| M7D | Blue Cross Blue Shield of North Dakota |
| M7E | Anthem Blue Cross of California |
| M7F | Blue Cross Blue Shield of Texas |
| M7G | Anthem Blue Cross Blue Shield of Indiana |
| M7H | Anthem Blue Cross Blue Shield of Indiana |
| M7I | Unassigned Prefix |
| M7J | Anthem Blue Cross Blue Shield of Indiana |
| M7K | Anthem Blue Cross Blue Shield of Indiana |
| M7L | Carefirst Blue Cross Blue Shield |
| M7M | Anthem Blue Cross Blue Shield of Colorado |
| M7N | Anthem Blue Cross Blue Shield of Virginia |
| M7O | Anthem Blue Cross Blue Shield of Virginia |
| M7P | Anthem Blue Cross Blue Shield of Ohio |
| M7Q | Anthem Blue Cross Blue Shield of Georgia |
| M7R | Carefirst Blue Cross Blue Shield |
| M7S | Blue Cross Blue Shield of Illinois |
| M7T | Anthem Blue Cross of California |
| M7U | Anthem Blue Cross Blue Shield of Indiana |
| M7V | Anthem Blue Cross Blue Shield of Missouri |
| M7W | Anthem Blue Cross Blue Shield of Indiana |
| M7X | Anthem Blue Cross Blue Shield of Kentucky |
| M7Y | Unassigned Prefix |
| M7Z | Anthem Blue Cross Blue Shield of Maine |
| M8A | Anthem Blue Cross Blue Shield of Colorado |
| M8B | Blue Cross Blue Shield of Illinois |
| M8C | Carefirst Blue Cross Blue Shield |
| M8D | Anthem Blue Cross Blue Shield of Maine |
| M8E | Anthem Blue Cross Blue Shield of Indiana |
| M8F | Blue Cross Blue Shield of Texas |
| M8G | Anthem Blue Cross Blue Shield of Virginia |
| M8H | Empire Blue Cross Blue Shield |
| M8I | Unassigned Prefix |
| M8J | Anthem Blue Cross Blue Shield of Virginia |
| M8K | Blue Cross Blue Shield of Texas |
| M8L | Anthem Blue Cross of California |
| M8M | Anthem Blue Cross Blue Shield of Indiana |
| M8N | Anthem Blue Cross Blue Shield of Virginia |
| M8O | Unassigned Prefix |
| M8P | Blue Cross Blue Shield of Minnesota |
| M8Q | Anthem Blue Cross Blue Shield of Georgia |
| M8R | Anthem Blue Cross Blue Shield of Virginia |
| M8S | Blue Cross Blue Shield of Illinois |
| M8T | Blue Cross Blue Shield of Illinois |
| M8U | Anthem Blue Cross Blue Shield of Indiana |
| M8V | Anthem Blue Cross Blue Shield of Connecticut |
| M8W | Anthem Blue Cross Blue Shield of Maine |
| M8X | Anthem Blue Cross Blue Shield of New Hampshire |
| M8Y | Blue Cross Blue Shield of Texas |
| M8Z | Anthem Blue Cross Blue Shield of Virginia |
| M9A | Empire Blue Cross Blue Shield |
| M9B | Blue Cross Blue Shield of Illinois |
| M9C | Empire Blue Cross Blue Shield |
| M9D | Anthem Blue Cross Blue Shield of Virginia |
| M9E | Anthem Blue Cross Blue Shield of Maine |
| M9F | Blue Cross Blue Shield of Texas |
| M9G | Anthem Blue Cross Blue Shield of Virginia |
| M9H | Blue Cross Blue Shield of Illinois |
| M9I | Unassigned Prefix |
| M9J | Anthem Blue Cross Blue Shield of Virginia |
| M9K | Blue Cross Blue Shield of Texas |
| M9L | Blue Cross Blue Shield of Texas |
| M9M | Anthem Blue Cross Blue Shield of Virginia |
| M9N | Anthem Blue Cross of California |
| M9O | Anthem Blue Cross Blue Shield of Virginia |
| M9P | Anthem Blue Cross Blue Shield of Indiana |
| M9Q | Anthem Blue Cross Blue Shield of Georgia |
| M9R | Anthem Blue Cross of California |
| M9S | Blue Cross Blue Shield of Illinois |
| M9T | Blue Cross Blue Shield of Texas |
| M9U | Anthem Blue Cross Blue Shield of Georgia |
| M9V | Unassigned Prefix |
| M9W | Anthem Blue Cross Blue Shield of Virginia |
| M9X | Couple Health |
| M9Y | Couple Health |
| M9Z | Couple Health |
