NPI registry status
Active
2026 NPPES data Emergency Medicine Physician NPI 1154514867 MD
Verify on CMS → Margaret Williamson, MD
Emergency Medicine Physician in Oak Lawn, 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 66,293 in Emergency Medicine 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
38
Medicare Part D claims · 30 beneficiaries · Emergency Medicine Physician avg: 355
Generic prescribing
66%
generic claims · 34% brand-name · higher generic rates reduce patient out-of-pocket costs
Source: CMS Medicare Part D Prescriber Public Use File, 2024
What the federal data shows
Margaret Williamson, MD filed 38 Medicare Part D claims in 2024 as an Emergency Medicine Physician in Oak Lawn, Illinois, prescribing 66% generic.
- 38
- Part D claims, 2024
- 66%
- generic prescribing
- Likely
- board-certified (heuristic)
- ≥0th
- pct by Part D claim volume (lower-bound band)
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.
Federal trust snapshot
What official records show about Margaret Williamson, MD
Federal records show an active NPI with Medicare Part D prescribing activity — verifiable registry data, not a proprietary rating.
- Verified
NPI registry status
Active listing in the CMS National Provider Identifier Registry (NPI 1154514867), first enumerated 08/26/2007.
Source: CMS NPPES
- Reported
Medicare Part D participation
Filed 38 Medicare Part D prescription claims in the 2023 CMS public use file — indicates active Medicare prescribing participation.
Source: CMS Part D Prescriber PUF
- Reported
Board certification signal
Heuristic suggests board-certified status based on ABMS-eligible specialty taxonomy plus active CMS participation signals — not a direct ABMS verification.
- Reported
Hospital affiliations
1 CMS Care Compare hospital affiliation on record — practice footprint from the Doctors and Clinicians file.
Source: CMS Care Compare
- State context
State board disciplinary context
Illinois statewide board action statistics are published annually — these figures describe aggregate state activity, not Margaret Williamson, MD's individual license status. Verify directly with the state medical board.
Source: IDFPR annual report 2023
- Not in federal data
Individual sanction lookup
PlainDoctor does not publish per-provider disciplinary determinations. Confirm current license and any individual actions through the state medical board or FSMB verification service.
Source: State medical board / FSMB
This trust snapshot summarizes only what appears in federal CMS/NPPES public records. It is not a composite score, star rating, patient review, or clinical recommendation. PlainDoctor never fabricates reviews or AggregateRating schema.
CMS NPPES provider registry desk
NPI 1154514867 · Emergency Medicine Physician
NPI-10 · ENUM-MID · TAX-MEGA · RX-TRACE · BOOK-LIGHT · PHOTO-ENUM
- NPI-10 1154514867
- ENUM-MID 2007
- TAX-MEGA 66K Emergency Medicine
- RX-TRACE 38
- BOOK-LIGHT 3,096 in Illinois
- PHOTO-ENUM Carrie Arnold, MD · 2007
Margaret Williamson, MD's Medicare Part D volume vs every U.S. prescriber
Total Medicare Part D claims, 2024, across all CMS prescribers nationally
38 ≥ 0th percentile 0% of 1,416,883 prescribers are in lower value bands
Each bar is a band; taller bars hold more prescribers. 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 100-claim band: it counts only prescribers in lower claim-volume bands. Medicare Part D claim volume is activity context, not a quality measure or recommendation. See methodology § corpus placement.
Source CMS Medicare Part D Prescriber Public Use File · 2024
✓
Board certification likely (heuristic, not verified)
Margaret Williamson, MD practices in an ABMS-board-eligible specialty and shows active CMS Medicare participation + 1 hospital affiliation - 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 Margaret Williamson, MD?
Quality data not reportedPrimary specialty
Emergency Medicine Physician
Medicare Part D claims
38 89% vs specialty avg
Specialty distribution in Illinois
How Emergency Medicine Physician compares to other specialties among Illinois providers
Board certification
Not published by CMS
CMS does not publish a per-provider board-certification field in NPPES. PlainDoctor does not have a reliable per-specialty certification rate to show for Emergency Medicine Physician. Verify directly:
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
Provider Details
| NPI | 1154514867 |
|---|---|
| Specialty | Emergency Medicine Physician |
| Credentials | MD |
| Gender | Female |
| NPI Issued | 08/26/2007 |
Hospital and facility affiliations
Facilities where Margaret Williamson, MD 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.
Northwestern Medical Faculty Foundation
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).
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 Margaret Williamson, MD. To verify Margaret Williamson, MD'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 · Above average
Margaret Williamson, MD - brand share 34.0%
Emergency Medicine Physician average
34% brand-name claims vs 66% generic, on 38 2024 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 2024.
38
Total Claims
$3K
Total Drug Cost
30
Medicare Beneficiaries
Prescribing Breakdown
- 30-Day Fills
- 44
- Total Day Supply
- 642
- Brand vs Generic
- 34% brand / 66% generic
- Brand Drug Cost
- $3K
- Generic Drug Cost
- $143
- Antibiotic Claims
- 15
Patient Demographics
- Average Patient Age
- 69.3 years
- Avg HCC Risk Score
- 1.69
- Gender Split
- 50% female / 50% male
Emergency Medicine Physician Overview
How Margaret Williamson, MD fits within the Emergency Medicine Physician landscape nationally.
66,293
Emergency Medicine Physician Providers in US
56
States with Emergency Medicine Physician
355
Avg Claims per Provider
Margaret Williamson, MD's 38 claims are below the specialty average of 355.
Nationwide Emergency Medicine Physician peers with similar MIPS or enrollment year
Two federal-record peer sets for Williamson, both outside Illinois so the neighborhoods are not geographic containment.
Same NPPES enumeration year (2007)
Same-specialty clinicians who entered the NPI registry in the same calendar year, outside this state.
Nearby Emergency Medicine Physician Providers in Illinois
Other clinicians with the same primary specialty enrolled in Illinois, drawn from the same CMS NPPES roster as Williamson.
One of 3,096 Emergency Medicine Physician providers enrolled in Illinois, 5 are shown here.
Dr. Osama Aaflaq
M.D.
Carbondale, IL
Dr. Suresh Abad
M.D.
Vernon Hills, IL
Dr. Albert Abalos
M.D.
Elmhurst, IL
Dr. Habib Abbasi
M.D.
Joliet, IL
Dr. Andrew Abbeg
D.O.
Greenville, IL
Compare Emergency Medicine Physician nationally: see state-by-state distribution →
Frequently Asked Questions
What is Margaret Williamson, MD's specialty? ▼
Margaret Williamson, MD specializes in Emergency Medicine Physician and practices in Oak Lawn, Illinois. Credentials: MD.
How much does Margaret Williamson, MD prescribe under Medicare Part D? ▼
In 2024, Margaret Williamson, MD wrote 38 Medicare Part D claims totaling $3K in drug costs for 30 beneficiaries.
Where is Margaret Williamson, MD located? ▼
Margaret Williamson, MD is located at 4440 W 95TH ST, Oak Lawn, IL, 60453. Phone: (434) 466-2969.
What is Margaret Williamson, MD's NPI number? ▼
Margaret Williamson, MD's National Provider Identifier (NPI) is 1154514867, issued on 08/26/2007.
Does Margaret Williamson, MD prescribe more brand-name or generic drugs? ▼
Margaret Williamson, MD's prescribing is 34% brand-name and 66% generic drugs by claim count, with $3K in brand drug costs.
How many Emergency Medicine Physician providers are there in the US? ▼
There are 66,293 Emergency Medicine Physician providers across 56 states in the US. The average Emergency Medicine Physician provider writes 355 Medicare Part D claims per year.
Does Margaret Williamson, MD accept Medicare? ▼
Margaret Williamson, MD appears in CMS Medicare data with 38 Part D claims and 30 Medicare beneficiaries in 2024. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify Margaret Williamson, MD's credentials? ▼
Margaret Williamson, MD's NPI is 1154514867 with credentials MD. 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 (2024). Includes claims, drug costs, beneficiaries, and opioid prescribing rates.
- 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 August 2026 (NPPES) / 2024 (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
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 August 2026.