Gretta Mae Colby, MD
Internal Medicine Physician · Milwaukee, WI
Gretta Mae Colby, MD is an internal medicine physician with a practice address in Milwaukee, Wisconsin, and NPI 1306587639, issued on Apr 1, 2022. Check the license (Wisconsin 83738-20, as entered in NPPES) on the Wisconsin Medical Examining Board; the Medicare figures below come from public CMS files.
- Name
- Gretta Mae Colby
- Credential
- MD
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- 83738-20 WI
Self-reported in NPPES; status is on the state search - Practice location
- 945 N 12TH St, Milwaukee, WI 53233
- Phone
- (414) 219-7427
- Enumerated
- Apr 1, 2022
- Record last updated
- Sep 18, 2025
- Medicaid ID
- 100310484 WI
- Medicare enrollment
- Enrolled (PECOS I20250802000102); accepts Medicare assignment
- Medical or professional school
- Medical College Of Wisconsin, 2022
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 2,078 in Wisconsin → Look up another NPI →
Also registered at 945 N 12TH St
A shared address usually means a shared clinic or building; it does not show who employs whom.
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- Ola AhmadStudent in an Organized Health Care Education/Training Program1629871645
Verify Gretta Mae Colby in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersWisconsin Medical Examining Board
Search for license 83738-20Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
100% fewer Medicare Part D claims than the average internal medicine physician in 2024
15 Medicare Part D claims, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D.
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
Bills Medicare through one group practice
- Aurora Medical Group, Inc.Milwaukee, WI
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Gretta Mae Colby among 2,078 internal medicine physician records in Wisconsin
Gretta Mae Colby, MD is one of 2,078 internal medicine physician records with a practice address in Wisconsin. 70% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2022, is newer than 89% of them.
- NPI issued2022 · 89% of these records are older, 8% newer
- In a Medicare fileYes · 70% of these records are
- In the CMS Doctors and Clinicians fileYes · 53% of these records are
- Graduated2022 · median 2002 among the 1,098 with a school on file
- Record last updated2025 · 55% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207R00000X and a Wisconsin practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
382 internal medicine physician records list a practice address in Milwaukee
They are 382 of the 18,389 NPPES records with a practice address in Milwaukee, and 2,078 internal medicine physician records in Wisconsin.
All 2,078 in Wisconsin → Every provider in Milwaukee → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Ruric (andy) Anderson, MDMilwaukee, WI 532331205995255
- Robin Brown, M.D.Milwaukee, WI 532331881776458
- Carolina Conti, M.D.Milwaukee, WI 532331750340766
- Ellen Danto-Nocton, M.D.Milwaukee, WI 532331265440002
- Mark Gennis, MDMilwaukee, WI 532331164570644
- Thomas Jackson, MDMilwaukee, WI 532331629186242
- Manuel Joseph, MDMilwaukee, WI 532331447391123
- Ariba Khan, MDMilwaukee, WI 532331891802328
Common questions
What is Gretta Mae Colby, MD's NPI number?
Gretta Mae Colby, MD's National Provider Identifier (NPI) is 1306587639, issued on Apr 1, 2022. An NPI identifies a provider in billing; it is not a license.
Where is Gretta Mae Colby, MD located?
The NPPES record lists a practice address at 945 N 12TH St, Milwaukee, WI, 53233. Phone: (414) 219-7427. Providers update this record themselves, so call before visiting.
How can I verify Gretta Mae Colby, MD's license?
NPPES lists Wisconsin license number 83738-20, as entered by the provider. Search the Wisconsin Medical Examining Board at https://dsps.wi.gov/Pages/BoardsCouncils/MEB/Default.aspx. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Gretta Mae Colby, MD prescribe under Medicare Part D?
In 2024, Gretta Mae Colby, MD had 15 Medicare Part D claims; the average among internal medicine physician prescribers was 3,176. Part D covers Medicare prescriptions only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.