Medicare Letters and Their Meaning

What do the Medicare letters mean?

The four different parts of Medicare are each identified by a letter: A, B, C and D. The number displayed on your Medicare card, however, is known as the Medicare Beneficiary Identifier and is randomly generated for you.

What is the meaning of these Medicare letters? Here we break them down so that you can have a clearer understanding of your Medicare coverage.

Man sitting at a table reviewing letters

What do the letters on your Medicare card mean?

The Medicare number displayed on Medicare cards (known as an MBI, or Medicare Beneficiary Identifier) is 11 characters long:

  • The 2nd, 5th, 8th and 9th characters are always a letter, and the 3rd and 6th characters are sometimes a letter.
  • All other characters will be numbers, and the letters S, L, O, I, B and Z will never be used.

The MBI is randomly generated and is “non-intelligent,” which means it contains no hidden or special meaning and is therefore more difficult for someone to use to steal your identity or commit fraud.

What the letters mean for the parts of Medicare

The four different parts of Medicare are each identified by a letter.

  • Medicare Part A is hospital insurance and provides coverage for inpatient stays at hospitals and skilled nursing care facilities, among other inpatient services.

  • Medicare Part B is medical insurance and provides coverage for outpatient doctor’s appointments and medical devices.

  • Medicare Part C, also known as Medicare Advantage, provides coverage for everything found in Part A and Part B through one plan provided by a private insurer.

    Many Medicare Advantage plans may also cover additional benefits not covered by Part A and Part B, such as prescription drugs, dental, vision, hearing, wellness programs like SilverSneakers and more.

  • Medicare Part D provides coverage exclusively for prescription drugs.

    You can visit to compare Part D plans available where you live and enroll in a Medicare prescription drug plan online in as little as 10 minutes.1

Medicare Supplement Insurance, also called Medigap, uses a letter system to identify its plans. Medicare Supplement Insurance is used in conjunction with Part A and Part B of Medicare to provide coverage for certain out-of-pocket expenses like some Medicare deductibles and coinsurance.

There are 10 Medicare Supplement Plans to choose from, identified by letters: Plan A, B, C, D, F, G, K, L, M and N. Note that Medigap coverage options are referred to as “plan” (e.g., Medigap Plan A) as opposed to “part” (Medicare Part A hospital insurance).

Call a licensed insurance agent

Do you have more questions about Medicare letters? Would you like to speak with a licensed insurance agent who can answer your Medicare questions and help you compare Medicare Advantage plan options available where you live?

Get started today. Call to speak with a licensed agent and compare your options.


Compare Medicare plans in your area

Compare Plans

Or call TTY Users: 711 to speak with a licensed insurance agent. We accept calls 24/7!