2026 NPPES data Adult Medicine Physician NPI 1891966792 M.D.
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DORIS WILLIAMS, M.D.

Adult Medicine Physician in CHATHAM, Illinois. CMS National Plan and Provider Enumeration System profile including specialty classification, practice address, and Medicare prescribing data when reported.

Federal data — no proprietary rating. PlainDoctor publishes the actual CMS NPPES and Medicare records — NPI registration, specialty, practice location, and prescribing data — without a composite score or editorial opinion on top. Every field traces to a federal source.
Prescribing volume
371
Medicare Part D claims · 30 beneficiaries · Adult Medicine Physician avg: 3K
Generic prescribing
80%
generic claims · 20% brand-name · higher generic rates reduce patient out-of-pocket costs

What the federal data shows

DORIS WILLIAMS, M.D. filed 371 Medicare Part D claims in 2023 as a Adult Medicine Physician in CHATHAM, Illinois, prescribing 80% generic.

371
Part D claims, 2023
80%
generic prescribing

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.

DORIS WILLIAMS, M.D.'s Medicare Part D volume vs every U.S. prescriber

Total Medicare Part D claims, 2023 — across all CMS prescribers nationally

371 Top 43% higher than 57% of 1,370,886 prescribers

0–200: 670,926 prescribers (49%). Below this entry. 200–400: 182,923 prescribers (13%). This entry sits in this band. 400–600: 90,619 prescribers (7%). Above this entry. 600–800: 56,224 prescribers (4%). Above this entry. 800–1,000: 40,919 prescribers (3%). Above this entry. 1,000–1,200: 31,827 prescribers (2%). Above this entry. 1,200–1,400: 26,224 prescribers (2%). Above this entry. 1,400–1,600: 21,710 prescribers (2%). Above this entry. 1,600–1,800: 19,072 prescribers (1%). Above this entry. 1,800–2,000: 16,451 prescribers (1%). Above this entry. 2,000–2,200: 213,991 prescribers (16%). Above this entry. This provider 0 2K+ every Part D prescriber (claims/yr), bucketed by value

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.

Source CMS Medicare Part D Prescriber Public Use File · 2023

Board-eligible specialty (heuristic — not verified)

DORIS WILLIAMS, M.D. practices in an ABMS-board-eligible specialty but we don't have enough CMS-participation signals to confirm active board-certified status. Consult CertificationMatters.org (the official ABMS public lookup).

What does the federal data show about DORIS WILLIAMS, M.D.?

Quality data not reported

NPI registry status

Active

Issued 03/19/2008

NPI 1891966792

Primary specialty

Adult Medicine Physician

Niche

2,481 US NPIs in this specialty

Medicare Part D claims

371 87% vs specialty avg

2023 prescription claims

Specialty avg: 2,807

Specialty distribution in Illinois

How Adult Medicine Physician compares to other specialties among Illinois providers

Illinois providers

Adult Medicine Physician share within Illinois

1. Adult Medicine Physician42%2. Internal medicine21%3. Family medicine17%4. Surgical12%5. Pediatric8%
Adult Medicine Physician share within Illinois

Specialty board-certification context

Estimated specialty board-certified rate — Adult Medicine Physician (ABMS / AOA reference)

Quality data not reported
Est. board-certified rate
78%
Adult Medicine Physician ABMS/AOA estimate

Est. board-certified rate (Adult Medicine Physician) — ABMS / AOA estimate

0%100%78%
Est. board-certified rate (Adult Medicine Physician) — ABMS / AOA estimate

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).

DORIS WILLIAMS, M.D. is a Adult Medicine Physician provider practicing in CHATHAM, Illinois, according to the CMS National Plan and Provider Enumeration System (NPPES). Credentials: M.D.. NPI: 1891966792. This profile includes practice location, specialty classification, and organizational affiliations from the CMS provider registry. Provider information is self-reported to CMS and updated monthly.

DORIS WILLIAMS, M.D. appears in the CMS NPPES registry as a Adult Medicine Physician provider holding M.D. credentials at 345 N MAIN ST, CHATHAM, IL, 62629, with a listed phone of (217) 483-3333. NPI 1891966792 was issued on 03/19/2008. Because NPPES data is self-reported by the provider and refreshed monthly, the address, phone, and specialty reflect what WILLIAMS most recently submitted to CMS rather than a vetted directory listing, which is why patients should always confirm the practice is still at this location before scheduling.

Medicare Part D records for calendar year 2023 show 371 prescription claims written by this provider, covering 30 Medicare beneficiaries and totaling roughly $8K in drug spend, split 20% brand-name and 80% generic by claim count. These figures capture only Medicare Part D — commercial insurance, Medicaid, and cash-pay prescriptions are not included, and any drug-beneficiary cell under 11 is suppressed by CMS for patient privacy.

Adult Medicine Physician is a narrow specialty nationwide, with 2,481 enrolled providers across 52 states and an average of 2,807 Part D claims per prescriber, so the context for interpreting these metrics differs meaningfully from a primary-care baseline. Important: PlainDoctor is a directory of publicly available government data, not medical advice, a malpractice database, or a quality rating. Inclusion here does not imply a recommendation, and absence of complaints or sanctions on this page does not mean none exist — always verify credentials through the NPPES NPI Registry, your state medical board, and the ABMS or AOA before making healthcare decisions.

Practice Address

345 N MAIN ST
CHATHAM, IL 62629

Provider Details

NPI 1891966792
Specialty Adult Medicine Physician
Credentials M.D.
Gender Female
NPI Issued 03/19/2008

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 DORIS WILLIAMS, M.D.. To verify DORIS WILLIAMS, 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

DORIS WILLIAMS, M.D. — brand share 20.0%
Specialty average (est.)

20% brand-name claims vs 80% generic, on 371 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.

371
Total Claims
$8K
Total Drug Cost
30
Medicare Beneficiaries

Prescribing Breakdown

30-Day Fills
381
Total Day Supply
7,895
Brand vs Generic
20% brand / 80% generic
Brand Drug Cost
$5K
Generic Drug Cost
$3K
Antibiotic Claims
26

Patient Demographics

Average Patient Age
47.6 years
Avg HCC Risk Score
0.91

Top Prescribed Drugs (Medicare Part D)

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

Drug Claims
Levothyroxine Sodium
48
Omeprazole
40
Metformin Hcl
30
Oxybutynin Chloride
23
Warfarin Sodium
14
Atorvastatin Calcium
13
Famotidine
13
Eliquis
Apixaban
12
Hydrochlorothiazide
11

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

Adult Medicine Physician Overview

How DORIS WILLIAMS, M.D. fits within the Adult Medicine Physician landscape nationally.

2,481
Adult Medicine Physician Providers in US
52
States with Adult Medicine Physician
2,807
Avg Claims per Provider

DORIS WILLIAMS, M.D.'s 371 claims are below the specialty average of 2,807.

Nearby Adult Medicine Physician Providers in Illinois

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

Compare Adult Medicine Physician nationally: see state-by-state distribution →

Frequently Asked Questions

What is DORIS WILLIAMS, M.D.'s specialty?
DORIS WILLIAMS, M.D. specializes in Adult Medicine Physician and practices in CHATHAM, Illinois. Credentials: M.D..
How much does DORIS WILLIAMS, M.D. prescribe under Medicare Part D?
In 2023, DORIS WILLIAMS, M.D. wrote 371 Medicare Part D claims totaling $8K in drug costs for 30 beneficiaries.
Where is DORIS WILLIAMS, M.D. located?
DORIS WILLIAMS, M.D. is located at 345 N MAIN ST, CHATHAM, IL, 62629. Phone: (217) 483-3333.
What is DORIS WILLIAMS, M.D.'s NPI number?
DORIS WILLIAMS, M.D.'s National Provider Identifier (NPI) is 1891966792, issued on 03/19/2008.
Does DORIS WILLIAMS, M.D. prescribe more brand-name or generic drugs?
DORIS WILLIAMS, M.D.'s prescribing is 20% brand-name and 80% generic drugs by claim count, with $5K in brand drug costs.
How many Adult Medicine Physician providers are there in the US?
There are 2,481 Adult Medicine Physician providers across 52 states in the US. The average Adult Medicine Physician provider writes 2,807 Medicare Part D claims per year.
What drugs does DORIS WILLIAMS, M.D. prescribe most often?
Based on 2023 Medicare Part D data, DORIS WILLIAMS, M.D.'s most frequently prescribed drugs include Levothyroxine Sodium, Omeprazole, Metformin Hcl. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does DORIS WILLIAMS, M.D. accept Medicare?
DORIS WILLIAMS, M.D. appears in CMS Medicare data with 371 Part D claims and 30 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify DORIS WILLIAMS, M.D.'s credentials?
DORIS WILLIAMS, M.D.'s NPI is 1891966792 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

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.
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