GRETTA MAE COLBY MD
NPI 1306587639
Internal Medicine in Milwaukee, WI
About Gretta Mae Colby Md NPPES
Official registry information on file with the National Plan and Provider Enumeration System.
GRETTA MAE COLBY MD (NPI 1306587639) is an individual internal medicine provider in Milwaukee, Wisconsin, licensed in Wisconsin (83738-20) and active in the NPI registry since April 2022. She is enrolled in Medicare PECOS, is affiliated with Aurora St Lukes Medical Center, and is a graduate of Medical College Of Wisconsin (2022).
NPPES Registry Identity
Specialties & Licenses
Other Names 1
Other Identifiers 1
Accepted Insurance
Medicare Participation & PECOS CMS
Medicare enrollment, assignment, and ordering and referring status from the CMS PECOS system.
Medicare Enrollment Status
Enrolled in Medicare and accepts Medicare assignment
Gretta Mae Colby Md is registered in PECOS and agrees to accept the Medicare-approved amount as full payment. Medicare patients are not billed beyond the standard deductible and coinsurance.
Hospital Affiliations CMS Care Compare
Hospitals where this provider delivers care, identified from recent Medicare claims and place-of-service records.
Aurora St Lukes Medical Center
Acute Care Hospitals · Milwaukee, WIPhysician Visit Costs CMS claims · ZIP area
Typical Medicare office-visit costs in the 53233 ZIP code area, from fee-for-service claims. These are area statistics, not this provider’s prices; actual charges vary by service and coverage.
Other Providers at the Same Location NPPES 20
Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.
MILWAUKEE, WI 53233
MILWAUKEE, WI 53233
Frequently Asked Questions NPPES & CMS
Common questions about this NPI record, answered from the official NPPES registry and CMS datasets shown on this page.
What is Gretta Colby's NPI number?
The NPI number for Gretta Colby is 1306587639. It was assigned to this individual provider in the NPPES registry on April 1, 2022. The provider is also known as Gretta Mae Nelson.
Where is Gretta Colby located?
Gretta Colby practices at 945 N 12th St, Milwaukee, WI 53233. The listed phone number is (414) 219-7427.
What is Gretta Colby's specialty?
The primary specialty registered for this NPI is Internal Medicine with taxonomy code 207R00000X.
Is Gretta Colby enrolled in Medicare?
Yes. Gretta Colby is registered in the Medicare PECOS system and accepts Medicare assignment, which means accepting the Medicare-approved amount as payment in full for covered services.
What insurance does Gretta Colby accept?
Health plans from Aspirus Health Plan and CareSource (Common Ground Healthcare) list Gretta Colby as in-network in at least one marketplace plan. Coverage varies by plan and year; verify with the insurer or the provider before a visit.
Is Gretta Colby affiliated with any hospitals?
According to CMS data, Gretta Colby is affiliated with Aurora St Lukes Medical Center.
When was this NPI record last updated?
The NPPES record for Gretta Colby was last updated on September 18, 2025. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 10 months ago. If this record has changed at CMS more recently, you can request an on-demand re-check against the live CMS registry, directly from this page.
# Gretta Mae Colby, MD · NPI 1306587639
Internal Medicine physician in Milwaukee, Wisconsin. Individual provider, active in the CMS NPPES registry since April 1, 2022.
## Identity
- **NPI:** 1306587639 (Entity type: Individual)
- **Enumerated:** April 1, 2022
- **Primary specialty:** Internal Medicine · taxonomy 207R00000X
- **State license:** 83738-20 (Wisconsin)
- **Sole proprietor:** Yes
## Practice location
- **Address:** 945 N 12TH ST, Milwaukee, WI 53233-1305
- **Phone:** (414) 219-7427
## Medicare
- **Medicare:** Enrolled (PECOS); accepts Medicare assignment
- **Ordering & referring:** eligible for Part B labs & imaging, durable medical equipment, home health, power mobility devices
- **Medical school:** Medical College Of Wisconsin, class of 2022
## Record status
- **NPPES last updated:** September 18, 2025
- **Other identifiers:** Medicaid 100310484 (WI)
---
Source: [NPI Profile](https://npiprofile.com/npi/1306587639) · Data from the CMS NPPES public registry.