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2026 NPPES data Obstetrics & Gynecology Physician NPI 1023007887 M.D.
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William Kobak, M.D.

Obstetrics & Gynecology Physician in St Charles, Illinois.

This profile is drawn from the federal National Provider Identifier Registry (CMS NPPES), which lists more than 7 million U.S. healthcare providers - including 44,326 in Obstetrics & Gynecology Physician, and covers specialty classification, practice address, and Medicare Part D prescribing data when reported. According to CMS, every field reflects the provider's official federal registration, see our methodology.

Federal data, no proprietary rating. We show these CMS records as-is - no composite score, no star rating, no editorial opinion layered on top.
Prescribing volume
300
Medicare Part D claims · 90 beneficiaries · Obstetrics & Gynecology Physician avg: 179
Generic prescribing
81%
generic claims · 19% brand-name · higher generic rates reduce patient out-of-pocket costs
MIPS score
80.8/100
▼ 3 pts below national avg 83.5 · Above neutral
Industry payments
$13.18
1 payments · CMS Open Payments (Sunshine Act)
Verify NPI on CMS Methodology
Compiled from official public sources by the editorial process.

What the federal data shows

William Kobak, M.D. reported a CMS MIPS final score of 80.8/100 - below the 83.5 national average - and filed 300 Medicare Part D claims in 2023.

80.8/100
MIPS score · -3 vs avg
300
Part D claims, 2023
81%
generic prescribing
Likely
board-certified (heuristic)

Every figure on this page comes straight from federal CMS records (NPPES, Medicare Part D, MIPS, Open Payments) - no proprietary rating or editorial opinion is applied.

CMS NPPES provider registry desk

NPI 1023007887 · Obstetrics & Gynecology Physician

NPI-10 · ENUM-LEGACY · TAX-MID · MIPS-INLINE · RX-LIGHT · BOOK-LIGHT · PHOTO-FINISH

  • NPI-10 1023007887
  • ENUM-LEGACY 2005
  • TAX-MID 44K Obstetrics &
  • MIPS-INLINE 80.8/100
  • RX-LIGHT 300
  • BOOK-LIGHT 1,925 in Illinois
  • PHOTO-FINISH Alaina Bennett · ±0.0

MIPS final-score neighbourhood

Same-specialty nationwide peers by CMS final score, not geographic proximity

MIPS pts

What this shows Nearest measured MIPS peers for this NUCC specialty (2023 performance year).

Source CMS Quality Payment Program (MIPS) As of 2023

William Kobak, M.D.'s MIPS score vs every measured U.S. clinician

CMS Merit-based Incentive Payment System (MIPS) final score, 2023, the federal quality measure. Clinicians whose score CMS assigned without scoring any category are excluded.

81 ≥ 30th percentile 30% of 454,083 measured providers are in lower value bands

0–10: 8,684 measured providers (2%). Below this entry. 10–20: 3,008 measured providers (1%). Below this entry. 20–30: 3,069 measured providers (1%). Below this entry. 30–40: 2,746 measured providers (1%). Below this entry. 40–50: 2,928 measured providers (1%). Below this entry. 50–60: 5,882 measured providers (1%). Below this entry. 60–70: 13,906 measured providers (3%). Below this entry. 70–80: 94,570 measured providers (21%). Below this entry. 80–90: 129,887 measured providers (29%). This entry sits in this band. 90+: 189,403 measured providers (42%). Above this entry. This provider 0 100 every measured MIPS clinician, bucketed by value

Each bar is a band; taller bars hold more measured providers. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.

The percentile is a conservative whole-score-point band: it counts only measured clinicians in lower score bands. A CMS MIPS metric is not a recommendation or a clinical-quality rating by PlainDoctor. See methodology § corpus placement.

Source CMS Merit-based Incentive Payment System (MIPS) · 2023

Where William Kobak, M.D. sits

This provider among obstetrics & gynecology physician peers

Across the 7,360 obstetrics & gynecology physician providers who report both Medicare Part D prescribing and a MIPS quality score, William Kobak, M.D. writes more Part D claims than 85% of them and scores higher on MIPS quality than 28% - placing this provider in the high-volume, lower-quality quadrant. Volume reflects patient-panel size and specialty, not quality; the two axes are independent.

Lower volume · High qualityHigh volume · High qualityLower volume · Lower qualityHigh volume · Lower quality02550751000255075100Part D claim volume, percentile in specialtyMIPS quality, percentilePoint, Part D claim volume, percentile in specialty: 100 · MIPS quality, percentile: 45Point, Part D claim volume, percentile in specialty: 67 · MIPS quality, percentile: 25Point, Part D claim volume, percentile in specialty: 63 · MIPS quality, percentile: 40Point, Part D claim volume, percentile in specialty: 37 · MIPS quality, percentile: 13Point, Part D claim volume, percentile in specialty: 0 · MIPS quality, percentile: 48Point, Part D claim volume, percentile in specialty: 70 · MIPS quality, percentile: 60Point, Part D claim volume, percentile in specialty: 7 · MIPS quality, percentile: 78Point, Part D claim volume, percentile in specialty: 12 · MIPS quality, percentile: 0Point, Part D claim volume, percentile in specialty: 92 · MIPS quality, percentile: 22Point, Part D claim volume, percentile in specialty: 43 · MIPS quality, percentile: 7Point, Part D claim volume, percentile in specialty: 88 · MIPS quality, percentile: 77Point, Part D claim volume, percentile in specialty: 10 · MIPS quality, percentile: 25Point, Part D claim volume, percentile in specialty: 20 · MIPS quality, percentile: 87Point, Part D claim volume, percentile in specialty: 42 · MIPS quality, percentile: 25Point, Part D claim volume, percentile in specialty: 35 · MIPS quality, percentile: 5Point, Part D claim volume, percentile in specialty: 97 · MIPS quality, percentile: 72Point, Part D claim volume, percentile in specialty: 8 · MIPS quality, percentile: 92Point, Part D claim volume, percentile in specialty: 53 · MIPS quality, percentile: 83Point, Part D claim volume, percentile in specialty: 18 · MIPS quality, percentile: 38Point, Part D claim volume, percentile in specialty: 15 · MIPS quality, percentile: 23Point, Part D claim volume, percentile in specialty: 55 · MIPS quality, percentile: 30Point, Part D claim volume, percentile in specialty: 2 · MIPS quality, percentile: 70Point, Part D claim volume, percentile in specialty: 27 · MIPS quality, percentile: 92Point, Part D claim volume, percentile in specialty: 68 · MIPS quality, percentile: 97Point, Part D claim volume, percentile in specialty: 3 · MIPS quality, percentile: 10Point, Part D claim volume, percentile in specialty: 40 · MIPS quality, percentile: 50Point, Part D claim volume, percentile in specialty: 13 · MIPS quality, percentile: 62Point, Part D claim volume, percentile in specialty: 72 · MIPS quality, percentile: 0Point, Part D claim volume, percentile in specialty: 57 · MIPS quality, percentile: 52Point, Part D claim volume, percentile in specialty: 87 · MIPS quality, percentile: 73Point, Part D claim volume, percentile in specialty: 45 · MIPS quality, percentile: 97Point, Part D claim volume, percentile in specialty: 85 · MIPS quality, percentile: 55Point, Part D claim volume, percentile in specialty: 72 · MIPS quality, percentile: 47Point, Part D claim volume, percentile in specialty: 20 · MIPS quality, percentile: 58Point, Part D claim volume, percentile in specialty: 47 · MIPS quality, percentile: 37Point, Part D claim volume, percentile in specialty: 17 · MIPS quality, percentile: 42Point, Part D claim volume, percentile in specialty: 48 · MIPS quality, percentile: 18Point, Part D claim volume, percentile in specialty: 38 · MIPS quality, percentile: 80Point, Part D claim volume, percentile in specialty: 52 · MIPS quality, percentile: 83Point, Part D claim volume, percentile in specialty: 50 · MIPS quality, percentile: 75Point, Part D claim volume, percentile in specialty: 28 · MIPS quality, percentile: 32Point, Part D claim volume, percentile in specialty: 98 · MIPS quality, percentile: 82Point, Part D claim volume, percentile in specialty: 95 · MIPS quality, percentile: 42Point, Part D claim volume, percentile in specialty: 23 · MIPS quality, percentile: 32Point, Part D claim volume, percentile in specialty: 83 · MIPS quality, percentile: 63Point, Part D claim volume, percentile in specialty: 3 · MIPS quality, percentile: 95Point, Part D claim volume, percentile in specialty: 75 · MIPS quality, percentile: 53Point, Part D claim volume, percentile in specialty: 25 · MIPS quality, percentile: 10Point, Part D claim volume, percentile in specialty: 58 · MIPS quality, percentile: 35Point, Part D claim volume, percentile in specialty: 32 · MIPS quality, percentile: 68Point, Part D claim volume, percentile in specialty: 77 · MIPS quality, percentile: 15Point, Part D claim volume, percentile in specialty: 30 · MIPS quality, percentile: 97Point, Part D claim volume, percentile in specialty: 80 · MIPS quality, percentile: 8Point, Part D claim volume, percentile in specialty: 62 · MIPS quality, percentile: 57Point, Part D claim volume, percentile in specialty: 60 · MIPS quality, percentile: 65Point, Part D claim volume, percentile in specialty: 82 · MIPS quality, percentile: 90Point, Part D claim volume, percentile in specialty: 33 · MIPS quality, percentile: 17Point, Part D claim volume, percentile in specialty: 93 · MIPS quality, percentile: 3Point, Part D claim volume, percentile in specialty: 78 · MIPS quality, percentile: 88Point, Part D claim volume, percentile in specialty: 65 · MIPS quality, percentile: 67William Kobak, M.D., Part D claim volume, percentile in specialty: 85 · MIPS quality, percentile: 28
Part D claim volume vs MIPS quality, by specialty percentile

Each dot is one obstetrics & gynecology physician peer from a representative sample of 60; the gold marker is William Kobak, M.D.. Source: CMS Medicare Part D Prescriber data and the CMS Merit-based Incentive Payment System, 2023.

✓
Board certification likely (heuristic, not verified)

William Kobak, M.D. practices in an ABMS-board-eligible specialty and shows active CMS Medicare participation + MIPS quality reporting + 2 hospital affiliations - signals consistent with board-certified status. For verified board certification, see CertificationMatters.org (the official ABMS public lookup).

What does the federal data show about William Kobak, M.D.?

Near national average

NPI registry status

Active

Issued 10/14/2005

NPI 1023007887

Primary specialty

Obstetrics & Gynecology Physician

Mid-sized

44,326 US NPIs in this specialty

Medicare Part D claims

300 68% vs specialty avg

2023 prescription claims

Specialty avg: 179

MIPS final score

80.8/100 2.7 pts vs avg

Above neutral band

vs 83.5 national avg

Specialty distribution in Illinois

How Obstetrics & Gynecology Physician compares to other specialties among Illinois providers

Illinois providers
Clinical Social Worker5.2%Physical Therapist5%Mental Health Counselor4.5%Speech-Language Pathologist4.2%Student in an Organized Heal…4.2%Pharmacist4.1%Obstetrics & Gynecology Phys…0.8%
Largest specialties in Illinois (% of in-state providers)

Medicare quality performance, MIPS

William Kobak, M.D.'s 2023 MIPS final score plotted against the Obstetrics & Gynecology Physician national average

Near national average
MIPS Final Score
80.8/100
vs 83.5 national avg · 2023 performance year
0%100%National avg84%80.8%
MIPS final score (Obstetrics & Gynecology Physician) - 80.8/100 vs national avg 83.5
How MIPS and board certification work

The Merit-based Incentive Payment System (MIPS) scores providers 0–100 across four performance categories: Quality, Cost, Promoting Interoperability, and Improvement Activities, weighted under 42 CFR §414.1380. Reporting is voluntary for many small practices, so absence of a MIPS score is not a quality signal.

Board certification through an ABMS or AOA member board signals voluntary post-licensure examination plus continuous Maintenance of Certification cycles. Verify any individual provider's status through certificationmatters.org (ABMS) or osteopathic.org (AOA).

Practice Address

3310 W MAIN ST
St Charles, IL 60175
(630) 897-6044

Provider Details

NPI 1023007887
Specialty Obstetrics & Gynecology Physician
Credentials M.D.
Gender Male
NPI Issued 10/14/2005

CMS Quality Score (MIPS)

Merit-based Incentive Payment System (MIPS) scores from CMS, 2023 performance year.

80.83
Final Score
Measured-score avg: 83.5
64.9666
Quality
63.1534
Cost
72
Promoting Interoperability

Reporting: Group practice

Hospital and facility affiliations

Facilities where William Kobak, M.D. bills Medicare from. Star ratings (1-5) are CMS Hospital Compare's "Hospital overall rating" - a composite of mortality, readmission, patient experience, safety, timely care, and efficient use of medical imaging measures. Source: CMS Care Compare.

Cook County
Chicago, IL
The Board OF Trustees OF The University OF Illinois
Chicago, IL

Affiliations sourced from CMS Doctors and Clinicians National Downloadable File; hospital ratings from CMS Hospital General Information dataset (cross-referenced by facility name + state).

Industry payments received (2024) - CMS Open Payments transparency data

The federal Physician Payments Sunshine Act (part of the Affordable Care Act) requires drug and medical-device manufacturers + group purchasing organizations to publicly report payments and other transfers of value to physicians and teaching hospitals. The data below covers 2024 for William Kobak, M.D.. Source: openpaymentsdata.cms.gov.

Total received

$13

Largest payer

Boston Scientific Corporation

Most common payment type

Food and Beverage

Industry payments are not necessarily indicators of bias, they include research funding, consulting fees for evidence-based work, royalties for inventions, food at conferences, and similar items. The disclosure exists for transparency. Read our methodology for how we interpret this data.

License & disciplinary context - Illinois IDFPR 2023 annual report

Aggregate state board data only, NOT a determination of any individual provider's status. The figures below describe statewide disciplinary activity across all ~42K Illinois medical licensees in 2023 - they are NOT specific to William Kobak, M.D.. To verify William Kobak, M.D.'s current license status, search the IDFPR public license lookup directly, or check the Federation of State Medical Boards (FSMB) verification service.

106
Total board actions, Illinois 2023
Across 103 cases
2.52
Actions per 1,000 licensees
Illinois statewide rate
probation
Most common action type
38 cases

IDFPR publishes annual disciplinary statistics as part of public-record reporting under each state's Administrative Procedure Act. See the full breakdown by action type and year on the Illinois disciplinary trends page. Cross-checked against FSMB U.S. Medical Regulatory Trends.

Brand vs generic prescribing mix · Typical

William Kobak, M.D. - brand share 19.0%
Obstetrics & Gynecology Physician average

19% brand-name claims vs 81% generic, on 300 2023 Medicare Part D claims.

The federal Medicare Part D Generic Dispensing Rate national benchmark sits near 90% generic / 10% brand for primary-care prescribers, per CMS Office of the Actuary 2024 estimates. Higher brand share is common in specialty prescribing where generic equivalents are not available.

Medicare Part D Prescribing Data

CMS Medicare Part D prescriber-level data for calendar year 2023.

300
Total Claims
$49K
Total Drug Cost
90
Medicare Beneficiaries

Prescribing Breakdown

30-Day Fills
520
Total Day Supply
14,588
Brand vs Generic
19% brand / 81% generic
Brand Drug Cost
$28K
Generic Drug Cost
$21K
Opioid Claims
13 (4.3% rate)
Antibiotic Claims
20

Patient Demographics

Average Patient Age
70.2 years
Avg HCC Risk Score
1.38
Gender Split
100% female / 0% male

Top Prescribed Drugs (Medicare Part D)

Top drugs by claim count for calendar year 2023. Based on Medicare Part D data only.

What William Kobak, M.D. prescribes most

Top Medicare Part D drugs by claim count, 2023

claims
Source CMS Medicare Part D Prescriber Public Use File As of 2023
Drug Claims
Estradiol
 61
Oxybutynin Chloride Er
Oxybutynin Chloride
43
Myrbetriq
Mirabegron
40
Solifenacin Succinate
 39
Methenamine Hippurate
 38
Nitrofurantoin Mono-Macro
Nitrofurantoin Monohyd/M-Cryst
14
Oxycodone Hcl
 13

* Counts below 11 are suppressed by CMS for patient privacy. Generic names shown where available from CMS Part D data.

More Obstetrics & Gynecology Physician in IL → All providers in Illinois → Compare specialties →

Obstetrics & Gynecology Physician Overview

How William Kobak, M.D. fits within the Obstetrics & Gynecology Physician landscape nationally.

44,326
Obstetrics & Gynecology Physician Providers in US
56
States with Obstetrics & Gynecology Physician
179
Avg Claims per Provider

William Kobak, M.D.'s 300 claims are above the specialty average of 179.

Nationwide Obstetrics & Gynecology Physician peers with similar MIPS or enrollment year

Two federal-record peer sets for Kobak, both outside Illinois so the neighborhoods are not geographic containment.

Similar MIPS final score

Nearest same-specialty clinicians by CMS MIPS final score (80.8 here).

Alaina Bennett 80.8 MT Kristie Bodnar 80.8 MT Jami Chisdak 80.8 MT Renee Frederickson 80.8 MT

Same NPPES enumeration year (2005)

Same-specialty clinicians who entered the NPI registry in the same calendar year, outside this state.

Janis Cornwell Arlington, TX David Kells Chandler, AZ Stephen Wagner Brandon, FL Lorraine Bevilacqua Tampa, FL

Nearby Obstetrics & Gynecology Physician Providers in Illinois

Other clinicians with the same primary specialty enrolled in Illinois, drawn from the same CMS NPPES roster as Kobak.

One of 1,925 Obstetrics & Gynecology Physician providers enrolled in Illinois, 5 are shown here.

Dr. Anum Abbasi
MD
Chicago, IL
Dr. Rana Abdul-Khalek
MD
Roscoe, IL
Dr. Idries Abdur-Rahman
M.D.
Ottawa, IL
Dr. Jamil Abdur-Rahman
M.D.
Gurnee, IL
Dr. Greta Abel
PA-C
Wheaton, IL

Compare Obstetrics & Gynecology Physician nationally: see state-by-state distribution →

Frequently Asked Questions

What is William Kobak, M.D.'s specialty? ▼
William Kobak, M.D. specializes in Obstetrics & Gynecology Physician and practices in St Charles, Illinois. Credentials: M.D..
How much does William Kobak, M.D. prescribe under Medicare Part D? ▼
In 2023, William Kobak, M.D. wrote 300 Medicare Part D claims totaling $49K in drug costs for 90 beneficiaries.
What is William Kobak, M.D.'s Medicare quality score? ▼
William Kobak, M.D. has a CMS MIPS Final Score of 80.8/100 (Quality: 65, Cost: 63.2). The average MIPS Final Score across the 454,083 clinicians with at least one published category score is 83.5; clinicians whose score CMS assigned without scoring any category are excluded from that average. Source: CMS Merit-based Incentive Payment System (MIPS) 2023.
Where is William Kobak, M.D. located? ▼
William Kobak, M.D. is located at 3310 W MAIN ST, St Charles, IL, 60175. Phone: (630) 897-6044.
What is William Kobak, M.D.'s NPI number? ▼
William Kobak, M.D.'s National Provider Identifier (NPI) is 1023007887, issued on 10/14/2005.
Does William Kobak, M.D. prescribe more brand-name or generic drugs? ▼
William Kobak, M.D.'s prescribing is 19% brand-name and 81% generic drugs by claim count, with $28K in brand drug costs.
Does William Kobak, M.D. prescribe opioids? ▼
Yes, William Kobak, M.D. had 13 opioid claims in 2023 with an opioid prescribing rate of 4.3%.
How many Obstetrics & Gynecology Physician providers are there in the US? ▼
There are 44,326 Obstetrics & Gynecology Physician providers across 56 states in the US. The average Obstetrics & Gynecology Physician provider writes 179 Medicare Part D claims per year.
What drugs does William Kobak, M.D. prescribe most often? ▼
Based on 2023 Medicare Part D data, William Kobak, M.D.'s most frequently prescribed drugs include Estradiol, Oxybutynin Chloride Er, Myrbetriq. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does William Kobak, M.D. accept Medicare? ▼
William Kobak, M.D. appears in CMS Medicare data with 300 Part D claims and 90 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify William Kobak, M.D.'s credentials? ▼
William Kobak, M.D.'s NPI is 1023007887 with credentials M.D.. You can verify this through the NPPES NPI Registry, check state medical board records, and confirm board certification through the ABMS or AOA.

Data Sources

View source datasets and methodology notes
Provider Directory
CMS National Plan and Provider Enumeration System (NPPES), download.cms.gov/nppes, updated monthly. Contains NPI, specialty, credentials, and practice location.
Specialty Classification
NUCC Health Care Provider Taxonomy (nucc.org), the industry standard for classifying provider specialties in Medicare and Medicaid billing.
Prescribing Data
CMS Medicare Part D Prescriber Public Use File (2023). Includes claims, drug costs, beneficiaries, and opioid prescribing rates.
Quality Performance
CMS Merit-based Incentive Payment System (MIPS) - 2023 performance year.
Limitations
Provider data is self-reported to CMS. Prescribing data reflects Medicare Part D only and does not include commercial insurance, Medicaid, or cash prescriptions. Claims below 11 beneficiaries are suppressed by CMS for privacy.

See our complete data methodology for details on how we collect and process government data.

Data as of April 2026 (NPPES) / 2023 (Medicare Part D). Source: Centers for Medicare & Medicaid Services (CMS).

Disclaimer: Data from CMS NPPES and Medicare Part D. PlainDoctor does not rate or rank providers. Provider information is self-reported and may not be current. Always verify information directly with the provider. About · Methodology

Compiled from official public sources by the editorial process.

Every figure on PlainDoctor is rendered directly from the federal CMS NPPES registry, Medicare Part D, MIPS, and Open Payments records, no number is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of May 2026.