Gretta Mae Colby, MD

Primary specialty

Internal Medicine PhysicianTaxonomy code 207R00000X

License

83738-20 Issued in WI

Practice address

945 N 12TH St
Milwaukee, WI 53233-1305

Phone

(414) 219-7427

NPI assigned

Apr 1, 2022

Sex

Female

Sole proprietor

Yes

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

Specialties & licenses 1

Addresses

Other identifiers 1

Other names 1

• Gretta Mae Nelson Former name

Electronic endpoints 2

Medicare fee-for-service enrollment

Enrolled in WI

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 1

Specialty

Internal Medicine

Education

Medical College of Wisconsin, 2022

Medicare assignment

Accepts the Medicare-approved amount as payment in full

Group practices

Aurora Medical Group, Inc.Group PAC ID 6709794258, 3,764 clinicians

Practice addresses (Care Compare)

Hospital & facility affiliations

• Aurora St Lukes Medical Center Hospital, Milwaukee, WI, CCN 520138

Medicare enrollment (NPD)

Enrolled

Credentials

Doctor of Medicine

Practice roles

Locations

Interoperability endpoints

• Direct secure messaging: gcolby339393@direct.myadvocateaurora.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.

• Aurora Medical Group, Inc.

  • Certified Registered Nurse Anesthetist
  • Milwaukee, WI
  • NPI 1427271378

  Internal Medicine

  Medicare reassignment Care Compare group NPD
• Aurora Medical Group, Inc.

  • Durable Medical Equipment & Medical Supplies
  • Oshkosh, WI
  • NPI 1326858044
  NPD
• Aurora Medical Group, Inc.

  • Durable Medical Equipment & Medical Supplies
  • Manitowoc, WI
  • NPI 1801941075
  NPD (past)

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

• Aurora Health Care Metro, Inc.

  • Mental Health Clinic/Center (Including Community Mental Health Center)
  • Cudahy, WI
  • NPI 1235355983

  Hospital

  Care Compare affiliation
• Aurora Health Care Metro, Inc.

  • General Acute Care Hospital
  • Milwaukee, WI
  • NPI 1861447179
  Care Compare affiliation

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

{
    "created_epoch": "1648771200000",
    "enumeration_type": "NPI-1",
    "last_updated_epoch": "1758153600000",
    "number": "1306587639",
    "addresses": [
        {
            "country_code": "US",
            "country_name": "United States",
            "address_purpose": "MAILING",
            "address_type": "DOM",
            "address_1": "945 N 12TH ST",
            "city": "MILWAUKEE",
            "state": "WI",
            "postal_code": "532331305",
            "telephone_number": "414-219-7427"
        },
        {
            "country_code": "US",
            "country_name": "United States",
            "address_purpose": "LOCATION",
            "address_type": "DOM",
            "address_1": "945 N 12TH ST",
            "city": "MILWAUKEE",
            "state": "WI",
            "postal_code": "532331305",
            "telephone_number": "414-219-7427"
        }
    ],
    "practiceLocations": [],
    "basic": {
        "last_name": "COLBY",
        "first_name": "GRETTA",
        "middle_name": "MAE",
        "credential": "MD",
        "sole_proprietor": "YES",
        "sex": "F",
        "enumeration_date": "2022-04-01",
        "last_updated": "2025-09-18",
        "certification_date": "2025-09-18",
        "status": "A"
    },
    "taxonomies": [
        {
            "code": "207R00000X",
            "taxonomy_group": "",
            "desc": "Internal Medicine",
            "state": "WI",
            "license": "83738-20",
            "primary": true
        }
    ],
    "identifiers": [
        {
            "code": "05",
            "desc": "MEDICAID",
            "issuer": null,
            "identifier": "100310484",
            "state": "WI"
        }
    ],
    "endpoints": [
        {
            "endpointType": "FHIR",
            "endpointTypeDescription": "FHIR URL",
            "endpoint": "https://EpicFHIR.aurora.org/FHIR/MYAURORA/api/FHIR/DSTU2/",
            "affiliation": "N",
            "address_1": "945 N 12th St",
            "city": "Milwaukee",
            "state": "WI",
            "country_code": "US",
            "postal_code": "532331305",
            "country_name": "United States",
            "address_type": "DOM"
        },
        {
            "endpointType": "DIRECT",
            "endpointTypeDescription": "Direct Messaging Address",
            "endpoint": "gcolby339393@direct.myadvocateaurora.org",
            "affiliation": "N",
            "use": "DIRECT",
            "useDescription": "Direct",
            "address_1": "945 N 12th St",
            "city": "Milwaukee",
            "state": "WI",
            "country_code": "US",
            "postal_code": "532331305",
            "country_name": "United States",
            "address_type": "DOM"
        }
    ],
    "other_names": [
        {
            "first_name": "GRETTA",
            "last_name": "NELSON",
            "middle_name": "MAE",
            "code": "1",
            "type": "Former Name"
        }
    ]
}

• Kevin Patrick Cohoon, D.O
• Helena M Coke, MD
• Lisa Alaine Colaluca, PA-C
• Angelo Joseph Colantonio
• Christina Colarossi, PA-C
• Maarten Colby, MD
• Alyssa Brooke Cole, PHARMD
• Dana Leola Cole
• Jody Cole
• Justin Michael Cole, CAA

• Internal Medicine Physician in Milwaukee, WI
• Providers in Milwaukee, WI by specialty
• Internal Medicine Physician in Wisconsin

• NPPES NPI Registry (CMS): identity, addresses, specialties, licenses, identifiers and endpoints. Last updated by the provider on Sep 18, 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.