- MAC
- Maximum Allowable Cost/Maximum Annual Copayment
- MB
- Medical Benefits
- MCO
- Managed Care Organization
- MCS
- Managed Care System
- MED-CHI
- Medical & Chirurgical Facility of Maryland
- MHA
- Maryland Hospital Association
- MHIN
- Maryland Health Information Network
- MM
- Major Medical
- MPOS
- Maryland Point of Service
- MSGR
- Maryland Small Group Reform
- MSSOP
- Mandatory Second Surgical Opinion Program