Daniel J. Grzegorek, D.O.
Internal Medicine Physician · Willowbrook, IL
Daniel J. Grzegorek, D.O. is an internal medicine physician with a practice address in Willowbrook, Illinois, and NPI 1487651337, issued on Jul 7, 2005. Check the license (Illinois 036-089211, as entered in NPPES) on the Illinois Department of Financial and Professional Regulation; the Medicare figures below come from public CMS files.
- Name
- Daniel J. Grzegorek
- Credential
- D.O.
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- 036-089211 IL
Self-reported in NPPES; status is on the state search - Practice location
- 6733 Kingery Hwy, Willowbrook, IL 60527
- Phone
- (630) 325-4049
- Enumerated
- Jul 7, 2005
- Record last updated
- Aug 8, 2023
- Medicaid ID
- 036089211 IL
- Medicare enrollment
- Enrolled (PECOS I20040403000087); accepts Medicare assignment
- Medical or professional school
- Chicago College Of Osteopathy, 1992
- Telehealth
- Offers telehealth (CMS)
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 7,238 in Illinois → Look up another NPI →
Also registered at 6733 Kingery Hwy
A shared address usually means a shared clinic or building; it does not show who employs whom.
- Pamela Piszczek, APRN, FNP-CNurse Practitioner1710528740
- Susan Wilkie, LMFTMarriage & Family Therapist1821009564
Verify Daniel J. Grzegorek in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersIllinois Department of Financial and Professional Regulation
Search for license 036-089211Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
3.7 times the Medicare Part D claims of the average internal medicine physician in 2024
11,602 Medicare Part D claims for 821 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D. Brand-name drugs were 11% of claims. 150 claims were for opioids.
Most prescribed
- Atorvastatin Calcium786 claims
- Levothyroxine Sodium607 claims
- Amlodipine Besylate476 claims
- Lisinopril388 claims
- Losartan Potassium340 claims
- Simvastatin334 claims
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
- Dupage Medical Group LtdSchaumburg, IL
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Daniel J. Grzegorek among 7,238 internal medicine physician records in Illinois
Daniel J. Grzegorek, D.O. is one of 7,238 internal medicine physician records with a practice address in Illinois. 73% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2005, is newer than 0% of them.
- NPI issued2005 · 0% of these records are older, 93% newer
- In a Medicare fileYes · 73% of these records are
- In the CMS Doctors and Clinicians fileYes · 50% of these records are
- Graduated1992 · median 2003 among the 3,580 with a school on file
- Record last updated2023 · 47% 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 Illinois practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
7 internal medicine physician records list a practice address in Willowbrook
They are 7 of the 453 NPPES records with a practice address in Willowbrook, and 7,238 internal medicine physician records in Illinois.
All 7,238 in Illinois → Every provider in Willowbrook → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Muhammad Ali, MDWillowbrook, IL 605271508898362
- Christopher Camilleri, DOBurr Ridge, IL 605271295710044
- Anthony Delorenzo, D.O.Willowbrook, IL 605271851477236
- Homer Diadula, M.D.Burr Ridge, IL 605271134105232
- Farzana Iqbal, M.D.Burr Ridge, IL 605271851359939
- Anto Maliakkal, M.D. H.M.D.CBurr Ridge, IL 605271558376368
- Linda Palumbo, M.D.Chicago, IL 605271215994264
- Jesse Park, MDBurr Ridge, IL 605271215042072
Common questions
What is Daniel J. Grzegorek, D.O.'s NPI number?
Daniel J. Grzegorek, D.O.'s National Provider Identifier (NPI) is 1487651337, issued on Jul 7, 2005. An NPI identifies a provider in billing; it is not a license.
Where is Daniel J. Grzegorek, D.O. located?
The NPPES record lists a practice address at 6733 Kingery Hwy, Willowbrook, IL, 60527. Phone: (630) 325-4049. Providers update this record themselves, so call before visiting.
How can I verify Daniel J. Grzegorek, D.O.'s license?
NPPES lists Illinois license number 036-089211, as entered by the provider. Search the Illinois Department of Financial and Professional Regulation at https://idfpr.illinois.gov/checklicense.html. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Daniel J. Grzegorek, D.O. prescribe under Medicare Part D?
In 2024, Daniel J. Grzegorek, D.O. had 11,602 Medicare Part D claims for 821 beneficiaries; 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.