Jacek Zajac, M.D.
NPI 1396817912 · Endocrinology, Diabetes & Metabolism Physician · Lombard, IL
Enrolled with Medicare as Practitioner - Endocrinology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Jacek Zajac, M.D. is a Endocrinology, Diabetes & Metabolism Physician provider in Lombard, IL (NPI 1396817912).
Provider details
- NPI number
- 1396817912
- Entity type
- Individual
- Primary specialty
- Endocrinology, Diabetes & Metabolism PhysicianAllopathic & Osteopathic Physicians
- Credential
- M.D.
- Sex
- Male
- Sole proprietor
- No
- License
- 361-07774 (IL)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure25% of score
19 yrs in NPPES registry
- Profile completeness25% of score
100% of core fields populated
- Practice footprint15% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)25% of score
1,183 Medicare services, 2024 (ranked within specialty)
- Open Payments transparency10% of score
Has Open Payments disclosures (2024)
Medicare volume is ranked against active providers in the same specialty. Signals a provider has no public data for (e.g. Medicare claims) are left out of the score entirely — never counted as zero — so providers without that data are not penalized. See the full formula and weights in our .
What this provider does (Medicare)
Based on Medicare fee-for-service claims, 2024; not all care is captured.
| Service (HCPCS) | Medicare services | Typical Medicare-allowed (2024) |
|---|---|---|
| Established Patient Office Or Other Outpatient Visit With Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 555 | $131 |
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 35 Minutes99232 | 361 | $79 |
| Established Patient Office Or Other Outpatient Visit With Low Level OD Decision Making, If Using Time, 20 Minutes Or More99213 | 100 | $92 |
| Initial Hospital Care With Moderate Level of Medical Decision Making, If Using Time, at Least 75 Minutes99223 | 57 | $172 |
| Initial Hospital Care With Straightforward Or Low-Level Medical Decision Making, If Using Time, at Least 55 Minutes99222 | 33 | $133 |
| New Patient Office Or Other Outpatient Visit With a High Level of Medical Decision Making, If Using Time, 60 Minutes Or More |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 98 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Metformin Hcl | 578 | 160 |
| Levothyroxine Sodium | 559 | 147 |
| Semaglutidebrand: Ozempic | 370 | 72 |
| Dulaglutidebrand: Trulicity | 263 | 48 |
| Empagliflozinbrand: Jardiance | 262 | 63 |
| Methimazole | 197 | 47 |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$4,453 across 223 records (Open Payments 2024)
Open Payments discloses payments and transfers of value (meals, travel, consulting, research, royalties) from drug and device makers to providers. This is a transparency signal, not a verdict — such payments are legal and common, and their presence is neither an endorsement nor a criticism. Source: CMS Open Payments, program year 2024.
Practice location
Mailing address
Registry dates
- Enumerated
- 2006-11-15
- Last updated
- 2024-02-20
- Certified
- 2024-02-20
Frequently asked questions
- What is Jacek Zajac's NPI number?
- Jacek Zajac's National Provider Identifier (NPI) is 1396817912, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Jacek Zajac's specialty?
- Jacek Zajac is listed in the NPPES registry with a primary specialty of Endocrinology, Diabetes & Metabolism Physician (Allopathic & Osteopathic Physicians).
- Where is Jacek Zajac located?
- Jacek Zajac's practice location on file with NPPES is 2500 S Highland Ave, Lombard, IL 60148-5381.
- What is Jacek Zajac's phone number?
- The practice phone number listed in the NPPES registry for Jacek Zajac is (630) 629-3610.
- Does Jacek Zajac accept Medicare?
- Jacek Zajac is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Jacek Zajac's NPI active?
- Yes — Jacek Zajac's NPI (1396817912) is active in the NPPES registry as of the last update on 2024-02-20.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.