Medicare Number (MBI)
Updated September 2026 · 2026 figures from CMS and Medicare.gov
Your Medicare number, officially the Medicare Beneficiary Identifier (MBI), is an 11-character mix of numbers and capital letters printed on your Medicare card. It's unique to you and is not your Social Security number.
MBI format
- 11 characters, shown in three groups on the card (for example Medicare's own sample: 1EG4-TE5-MK73)
- The dashes aren't part of the number; don't type them into forms
- Characters are numbers 0–9 and uppercase letters; the letters S, L, O, I, B and Z are never used, to avoid confusion with numbers
- The first character is always a number from 1 to 9
Where to find your Medicare number
- On your red, white and blue Medicare card
- In your Medicare.gov account
- On a Medicare Summary Notice or letters from Medicare
- By calling 1-800-MEDICARE (1-800-633-4227), after identity checks
- Your doctor's office may be able to look it up through their secure provider portal
Your Medicare Advantage or Part D plan card shows a different member ID from the plan. Your MBI stays the same whichever plan you choose.
Old Medicare numbers
Before 2018 Medicare used the Health Insurance Claim Number (HICN), based on your Social Security number. It's no longer accepted for claims; always use your MBI.
Keep your Medicare number safe
- Only give it to doctors, pharmacies, insurers you've chosen, and trusted people helping with your care.
- Medicare won't call you to ask for your number.
- If you think it's been stolen or misused, call 1-800-MEDICARE; Medicare can issue you a new MBI.
- Check your Medicare Summary Notices for services you didn't receive.
Frequently asked questions
What does a Medicare number look like?
11 characters of numbers and capital letters, like Medicare's example 1EG4-TE5-MK73, printed on your Medicare card.
Is my Medicare number my Social Security number?
No. Since 2018 Medicare uses a separate Medicare Beneficiary Identifier.
How can I find my Medicare number without my card?
Log into your Medicare.gov account or call 1-800-MEDICARE.