Medicare Letters and Their Meaning

Between premiums, deductibles and coinsurance amounts, Medicare can be a numbers game. But there are also some letters associated with Medicare that are important for all beneficiaries to understand.

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 the letters on your Medicare card mean

Until 2019, Medicare cards contained letters that carried a meaning based on your type of coverage. But the letters on new Medicare cards, which all beneficiaries should receive in the mail by April of 2019, will carry no such meaning.

The Medicare number displayed on Medicare cards in 2019 and after (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.

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. Speak with a licensed agent by calling TTY Users: 711 24 hours a day, 7 days a week.

Copyright © 2019 TZ Insurance Solutions LLC. All rights reserved. is a website owned and operated by TZ Insurance Solutions LLC. TZ Insurance Solutions LLC and TruBridge, Inc. represent Medicare Advantage Organizations and Prescription Drug Plans having Medicare contracts; enrollment in any plan depends upon contract renewal.

Plan availability varies by region and state. For a complete list of available plans, please contact 1-800-MEDICARE (TTY users should call 1-877-486-2048), 24 hours a day/7 days a week or consult

Medicare has neither reviewed nor endorsed this information.