William Hemsley Merwin III, M.D.

Primary specialty

Student in an Organized Health Care Education/Training ProgramTaxonomy code 390200000X

Practice address

201 E University Pkwy Dept of
Baltimore, MD 21218

Phone

(410) 554-2284

Fax

(410) 554-2184

NPI assigned

May 4, 2015

Sex

Male

Sole proprietor

Yes

Registry information is reported by the provider to CMS and is not verified. About this source

Specialties & licenses 2

Addresses

Medicare fee-for-service enrollment

Enrolled in MD, DC2 enrollments

Eligible to order & refer

• Part B services: Yes
• Medical equipment: Yes
• Home health: Yes
• Power mobility devices: Yes
• Hospice: Yes

Green means eligible to order or refer.

Enrollment records 2

Specialty

Hospitalist

Education

Georgetown University School of Medicine, 2015

Medicare assignment

Accepts the Medicare-approved amount as payment in full

Group practices

Medstar Medical Group II LLCGroup PAC ID 0547413825, 3,726 clinicians

Practice addresses (Care Compare)

Hospital & facility affiliations

• Medstar Franklin Square Medical Center Hospital, Rosedale, MD, CCN 210015

Medicare enrollment (NPD)

Enrolled

Credentials

Doctor of Medicine

State licenses

Practice roles

Interoperability endpoints

• Direct secure messaging: wmerwin557679@direct.hopkinsmedicine.org

Organizations this provider is connected to: Medicare benefit reassignments (the organization bills Medicare for this provider’s services), Care Compare group memberships and National Provider Directory roles.

• Medstar Medical Group II LLC

  • General Practice Physician
  • Baltimore, MD
  • NPI 1184046187

  DC

  Medicare reassignment Care Compare group
• Frederick Health Hospital Inc

  • General Acute Care Hospital
  • Frederick, MD
  • NPI 1538165527
  NPD (past)

Hospitals and other facilities this clinician is affiliated with according to Medicare Care Compare.

• Franklin Square Hospital Center, Inc

  • General Acute Care Hospital
  • Baltimore, MD
  • NPI 1184712085
  Care Compare affiliation

The complete NPPES record for this NPI in the NPI Registry API format.

{
    "created_epoch": "1430697600000",
    "enumeration_type": "NPI-1",
    "last_updated_epoch": "1749600000000",
    "number": "1043697600",
    "addresses": [
        {
            "country_code": "US",
            "country_name": "United States",
            "address_purpose": "MAILING",
            "address_type": "DOM",
            "address_1": "201 E UNIVERSITY PKWY",
            "city": "BALTIMORE",
            "state": "MD",
            "postal_code": "212182829",
            "telephone_number": "410-554-2284",
            "fax_number": "410-554-2184"
        },
        {
            "country_code": "US",
            "country_name": "United States",
            "address_purpose": "LOCATION",
            "address_type": "DOM",
            "address_1": "201 E UNIVERSITY PKWY DEPT OF",
            "city": "BALTIMORE",
            "state": "MD",
            "postal_code": "21218",
            "telephone_number": "410-554-2284",
            "fax_number": "410-554-2184"
        }
    ],
    "practiceLocations": [],
    "basic": {
        "last_name": "MERWIN",
        "first_name": "WILLIAM",
        "middle_name": "HEMSLEY",
        "name_prefix": "Dr.",
        "name_suffix": "III",
        "credential": "M.D.",
        "sole_proprietor": "YES",
        "sex": "M",
        "enumeration_date": "2015-05-04",
        "last_updated": "2025-06-11",
        "certification_date": "2025-06-11",
        "status": "A"
    },
    "taxonomies": [
        {
            "code": "207R00000X",
            "taxonomy_group": "",
            "desc": "Internal Medicine",
            "state": "MD",
            "license": "D0091613",
            "primary": false
        },
        {
            "code": "390200000X",
            "taxonomy_group": "",
            "desc": "Student in an Organized Health Care Education/Training Program",
            "state": "MD",
            "license": null,
            "primary": true
        }
    ],
    "identifiers": [],
    "endpoints": [],
    "other_names": []
}

• Merryman & Allen LLC
• Ginny M Merryman, M.D.
• Jessica Lynn Mersinger, BSN, RN
• Anis S Merson, M.D.
• Rachel Urban Mertins, PT, DPT
• Hector Alonso Mesa Corrales, MD
• Daniel Mesa, PHARMD
• Franklin Mesa, PHD
• Jesse Vasques Mesenburg, FNP-C
• Benny Mesfin, PMHNP-BC

• Student in an Organized Health Care Education/Training Program in Baltimore, MD
• Providers in Baltimore, MD by specialty
• Student in an Organized Health Care Education/Training Program in Maryland

• NPPES NPI Registry (CMS): identity, addresses, specialties, licenses, identifiers and endpoints. Last updated by the provider on Jun 11, 2025; self-reported and not verified by CMS. Specialty names from the NUCC taxonomy.
• Medicare enrollment (CMS PECOS): enrollments, PAC IDs and benefit reassignments; Order and Referring.
• Medicare Care Compare (CMS): clinician profile, group practices, facility affiliations, MIPS scores and star ratings.
• National Provider Directory (CMS): practice roles, locations, licenses, networks and endpoints.

Verify at the official NPI Registry.