Jacek Zajac, M.D.
Endocrinology, Diabetes & Metabolism Physician · Lombard, IL
Jacek Zajac, M.D. is an endocrinology, diabetes & metabolism physician with a practice address in Lombard, Illinois, and NPI 1396817912, issued on Nov 15, 2006. Check the license (Illinois 361-07774, as entered in NPPES) on the Illinois Department of Financial and Professional Regulation; the Medicare figures below come from public CMS files.
- Name
- Jacek Zajac
- Credential
- M.D.
- Primary taxonomy
- Endocrinology, Diabetes & Metabolism Physician 207RE0101X
- License number
- 361-07774 IL
Self-reported in NPPES; status is on the state search - Practice location
- 2500 S Highland Ave, Lombard, IL 60148
- Phone
- (630) 629-3610
- Enumerated
- Nov 15, 2006
- Record last updated
- Feb 20, 2024
- Fax
- (630) 629-4878
- Medicare enrollment
- Enrolled (PECOS I20051215000606); accepts Medicare assignment
- Entity
- Type 1 · individual
8 nearest endocrinology, diabetes & metabolism physician records → All 436 in Illinois → Look up another NPI →
Also registered at 2500 S Highland Ave
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Jacek Zajac 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 361-07774Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
2.4 times the Medicare Part D claims of the average endocrinology, diabetes & metabolism physician in 2024
6,334 Medicare Part D claims for 591 beneficiaries, against an average of 2,630 among the 8,223 providers of this specialty who prescribed in Part D. Brand-name drugs were 39% of claims.
Most prescribed
- Metformin Hcl578 claims
- Levothyroxine Sodium559 claims
- Ozempic370 claims
- Trulicity263 claims
- Jardiance262 claims
- Methimazole197 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.
Industry payments in 2024: $4,452.55
223 payments; by number, the most common kind was food and beverage; the largest payer was Lilly USA, LLC. The 5,661 providers of this specialty with any payment received $5,742.15 on average. Payments are reported by manufacturers, not by the provider, and are not a sign of wrongdoing.
Source: CMS Open Payments, program year 2024 (openpaymentsdata.cms.gov); average among providers of this specialty with at least one payment.
Bills Medicare through one group practice
- Endocrinology Associates SCLombard, IL
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Jacek Zajac among 436 endocrinology, diabetes & metabolism physician records in Illinois
Jacek Zajac, M.D. is one of 436 endocrinology, diabetes & metabolism physician records with a practice address in Illinois. 85% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2006, is newer than 5% of them.
- NPI issued2006 · 5% of these records are older, 62% newer
- In a Medicare fileYes · 85% of these records are
- In the CMS Doctors and Clinicians fileYes · 68% of these records are
- Graduated1991 · median 2006 among the 295 with a school on file
- Record last updated2024 · 46% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207RE0101X and a Illinois practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Endocrinology, Diabetes & Metabolism Physician providers in Illinois
There are 436 endocrinology, diabetes & metabolism physician records in Illinois.
All 436 in Illinois → Every provider in Lombard → Endocrinology, Diabetes & Metabolism Physician nationwide →
The 8 endocrinology, diabetes & metabolism physician records with the nearest ZIP codes
- Sabaa Joad, M.D.Lombard, IL 601481629314372
- Terrence Swade, M.D.Lombard, IL 601481699847202
- Alberto Andrade, MDMaywood, IL 601531275363723
- Rod Marianne Arceo-Mendoza, M.D.Maywood, IL 601531154641876
- Pauline Camacho, MDMaywood, IL 601531730168816
- Gerald Charnogursky, MDMaywood, IL 601531023097102
- Mary Ann Emanuele, MDMaywood, IL 601531902885080
- Ellil KrishnarajuMaywood, IL 601531720654858
Common questions
What is Jacek Zajac, M.D.'s NPI number?
Jacek Zajac, M.D.'s National Provider Identifier (NPI) is 1396817912, issued on Nov 15, 2006. An NPI identifies a provider in billing; it is not a license.
Where is Jacek Zajac, M.D. located?
The NPPES record lists a practice address at 2500 S Highland Ave, Lombard, IL, 60148. Phone: (630) 629-3610. Providers update this record themselves, so call before visiting.
How can I verify Jacek Zajac, M.D.'s license?
NPPES lists Illinois license number 361-07774, 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 Jacek Zajac, M.D. prescribe under Medicare Part D?
In 2024, Jacek Zajac, M.D. had 6,334 Medicare Part D claims for 591 beneficiaries; the average among endocrinology, diabetes & metabolism physician prescribers was 2,630. 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.