A Medicare number, officially the Medicare Beneficiary Identifier (MBI), is an 11-character code of numbers and uppercase letters printed on the front of your red, white, and blue Medicare card, just below your name. It looks something like 1EG4-TE5-MK73. The dashes are added for readability and aren’t part of the number itself.1Centers for Medicare & Medicaid Services. Medicare Beneficiary Identifiers (MBIs)
Every MBI is randomly generated. The characters don’t encode your age, your state, your Social Security Number, or anything else about you.2Social Security Administration. POMS HI 00901.040 – New Medicare Numbers and Number Change Requests
The 11-Character Pattern
Every valid MBI follows the same fixed sequence of numbers and letters. If you want to check a number you have in front of you, walk it through this pattern one character at a time:
- Position 1: a number from 1 through 9 (never zero)
- Position 2: a letter
- Position 3: a letter or number
- Position 4: a number from 0 through 9
- Position 5: a letter
- Position 6: a letter or number
- Position 7: a number from 0 through 9
- Position 8: a letter
- Position 9: a letter
- Position 10: a number from 0 through 9
- Position 11: a number from 0 through 9
Six letters never appear anywhere in an MBI: S, L, O, I, B, and Z. They look too much like numbers and cause processing errors.3Centers for Medicare & Medicaid Services. Understanding the Medicare Beneficiary Identifier (MBI) Format All letters are uppercase.
Quick Ways to Spot an Invalid Number
If the first character is a zero, it’s not a real MBI. If you see an S, L, O, I, B, or Z anywhere in the number, it’s not a real MBI. If the sequence of letters and numbers doesn’t line up with the positions above, something is wrong with the card or the number was written down incorrectly.3Centers for Medicare & Medicaid Services. Understanding the Medicare Beneficiary Identifier (MBI) Format
One other check: the card itself is paper, red, white, and blue. There is no chip, no magnetic strip, and no plastic version. If you have an old card that shows a Social Security Number instead of an MBI, that card no longer works. Those numbers were retired for Medicare billing on January 1, 2020, and you need the newer card.1Centers for Medicare & Medicaid Services. Medicare Beneficiary Identifiers (MBIs)
Cards issued through the Railroad Retirement Board look the same and use the same MBI format, with the words “Railroad Retirement Board” printed on the face.4RRB.Gov. New Medicare Card Sample
Where to Find Your Medicare Number Without the Card
The card is the obvious place. If you don’t have it, you have three other ways to get your number:
- Sign in to your account at Medicare.gov to view and print an official copy of your card.5Medicare. Your Medicare Card
- Sign in to your Social Security account at ssa.gov and pull your benefit verification letter, which lists your Medicare number.6Social Security Administration. Manage Your Medicare Benefits
- Call 1-800-MEDICARE (1-800-633-4227; TTY 1-877-486-2048) for your number or to order a replacement card by mail.5Medicare. Your Medicare Card
If You Have a Medicare Advantage Plan
The MBI is still your Medicare number even if you’re enrolled in a Medicare Advantage plan, but you don’t hand the red, white, and blue card to your doctor or pharmacy. You use the card your Advantage plan sent you. Keep the Medicare card in a safe place anyway. You’ll need the MBI if you switch plans, return to Original Medicare, or get admitted to a hospital that needs to confirm your underlying eligibility.5Medicare. Your Medicare Card
Treat the Number Like a Credit Card Number
CMS classifies the MBI as Personally Identifiable Information.1Centers for Medicare & Medicaid Services. Medicare Beneficiary Identifiers (MBIs) Only give it to your doctors, your plan, or a government agency you contacted first. If someone calls you out of the blue saying you need a new “plastic” or “chip-enabled” Medicare card and asks you to confirm your number or pay a fee, it’s a scam. The real card is paper, it’s free, and Medicare will never call you unsolicited to ask for personal information or payment.7Consumer Advice. Hang Up on Medicare Card Scams
If your MBI has already been compromised, call 1-800-MEDICARE and request a new one. CMS will issue a card with a completely different 11-character number, and the old MBI stops working once the new one is active.2Social Security Administration. POMS HI 00901.040 – New Medicare Numbers and Number Change Requests