2026 NPPES data Rheumatology Physician NPI 1043303803 M.D.
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GARY FAHRENBACH, M.D.

Rheumatology Physician in NILES, 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
2K
Medicare Part D claims · 217 beneficiaries · Rheumatology Physician avg: 2K
Generic prescribing
91%
generic claims · 9% brand-name · higher generic rates reduce patient out-of-pocket costs
Industry payments
$93.37
4 payments · CMS Open Payments (Sunshine Act)

What the federal data shows

GARY FAHRENBACH, M.D. filed 1,758 Medicare Part D claims in 2023 as a Rheumatology Physician in NILES, Illinois, prescribing 91% generic.

2K
Part D claims, 2023
91%
generic prescribing
$93.37
industry payments (Sunshine Act)

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.

GARY FAHRENBACH, M.D.'s Medicare Part D volume vs every U.S. prescriber

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

1,758 Top 17% higher than 83% of 1,370,886 prescribers

0–200: 670,926 prescribers (49%). Below this entry. 200–400: 182,923 prescribers (13%). Below this entry. 400–600: 90,619 prescribers (7%). Below this entry. 600–800: 56,224 prescribers (4%). Below this entry. 800–1,000: 40,919 prescribers (3%). Below this entry. 1,000–1,200: 31,827 prescribers (2%). Below this entry. 1,200–1,400: 26,224 prescribers (2%). Below this entry. 1,400–1,600: 21,710 prescribers (2%). Below this entry. 1,600–1,800: 19,072 prescribers (1%). This entry sits in this band. 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)

GARY FAHRENBACH, 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 GARY FAHRENBACH, M.D.?

Quality data not reported

NPI registry status

Active

Issued 10/02/2006

NPI 1043303803

Primary specialty

Rheumatology Physician

Mid-sized

6,181 US NPIs in this specialty

Medicare Part D claims

1,758 14% vs specialty avg

2023 prescription claims

Specialty avg: 2,054

Specialty distribution in Illinois

How Rheumatology Physician compares to other specialties among Illinois providers

Illinois providers

Rheumatology Physician share within Illinois

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

Specialty board-certification context

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

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

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

0%100%78%
Est. board-certified rate (Rheumatology 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).

GARY FAHRENBACH, M.D. appears in the CMS NPPES registry as a Rheumatology Physician provider holding M.D. credentials at 7411 N MILWAUKEE AVE, NILES, IL, 60714, with a listed phone of (773) 763-1818. NPI 1043303803 was issued on 10/02/2006. Because NPPES data is self-reported by the provider and refreshed monthly, the address, phone, and specialty reflect what FAHRENBACH 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 1,758 prescription claims written by this provider, covering 217 Medicare beneficiaries and totaling roughly $977K in drug spend, split 9% brand-name and 91% generic by claim count, with an opioid prescribing rate of 10.9%. 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.

Rheumatology Physician is a mid-sized specialty nationwide, with 6,181 enrolled providers across 52 states and an average of 2,054 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

7411 N MILWAUKEE AVE
NILES, IL 60714

Provider Details

NPI 1043303803
Specialty Rheumatology Physician
Credentials M.D.
Gender Male
NPI Issued 10/02/2006

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 GARY FAHRENBACH, M.D.. Source: openpaymentsdata.cms.gov.

Total received

$93

Largest payer

Regeneron Healthcare Solutions, Inc.

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 GARY FAHRENBACH, M.D.. To verify GARY FAHRENBACH, 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 · Generic-heavy

GARY FAHRENBACH, M.D. — brand share 9.0%
Specialty average (est.)

9% brand-name claims vs 91% generic, on 1,758 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.

1,758
Total Claims
$977K
Total Drug Cost
217
Medicare Beneficiaries

Prescribing Breakdown

30-Day Fills
2,508
Total Day Supply
72,852
Brand vs Generic
9% brand / 91% generic
Brand Drug Cost
$933K
Generic Drug Cost
$44K
Opioid Claims
192 (10.9% rate)
Antibiotic Claims
19

Patient Demographics

Average Patient Age
74.1 years
Avg HCC Risk Score
1.44
Gender Split
71% female / 29% male
Age Distribution
<65: 14, 65-74: 108, 75-84: 70, 85+: 25

Top Prescribed Drugs (Medicare Part D)

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

What GARY FAHRENBACH, 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
Prednisone
405
Methotrexate
Methotrexate Sodium
227
Leflunomide
159
Tramadol Hcl
104
Hydroxychloroquine Sulfate
84
Acetaminophen-Codeine
Acetaminophen With Codeine
76
Azathioprine
73
Enbrel
Etanercept
52
Allopurinol
44
Diclofenac Sodium
42

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

Rheumatology Physician Overview

How GARY FAHRENBACH, M.D. fits within the Rheumatology Physician landscape nationally.

6,181
Rheumatology Physician Providers in US
52
States with Rheumatology Physician
2,054
Avg Claims per Provider

GARY FAHRENBACH, M.D.'s 1,758 claims are below the specialty average of 2,054.

Nearby Rheumatology Physician Providers in Illinois

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

Compare Rheumatology Physician nationally: see state-by-state distribution →

Frequently Asked Questions

What is GARY FAHRENBACH, M.D.'s specialty?
GARY FAHRENBACH, M.D. specializes in Rheumatology Physician and practices in NILES, Illinois. Credentials: M.D..
How much does GARY FAHRENBACH, M.D. prescribe under Medicare Part D?
In 2023, GARY FAHRENBACH, M.D. wrote 1,758 Medicare Part D claims totaling $977K in drug costs for 217 beneficiaries.
Where is GARY FAHRENBACH, M.D. located?
GARY FAHRENBACH, M.D. is located at 7411 N MILWAUKEE AVE, NILES, IL, 60714. Phone: (773) 763-1818.
What is GARY FAHRENBACH, M.D.'s NPI number?
GARY FAHRENBACH, M.D.'s National Provider Identifier (NPI) is 1043303803, issued on 10/02/2006.
Does GARY FAHRENBACH, M.D. prescribe more brand-name or generic drugs?
GARY FAHRENBACH, M.D.'s prescribing is 9% brand-name and 91% generic drugs by claim count, with $933K in brand drug costs.
Does GARY FAHRENBACH, M.D. prescribe opioids?
Yes, GARY FAHRENBACH, M.D. had 192 opioid claims in 2023 with an opioid prescribing rate of 10.9%.
How many Rheumatology Physician providers are there in the US?
There are 6,181 Rheumatology Physician providers across 52 states in the US. The average Rheumatology Physician provider writes 2,054 Medicare Part D claims per year.
What drugs does GARY FAHRENBACH, M.D. prescribe most often?
Based on 2023 Medicare Part D data, GARY FAHRENBACH, M.D.'s most frequently prescribed drugs include Prednisone, Methotrexate, Leflunomide. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does GARY FAHRENBACH, M.D. accept Medicare?
GARY FAHRENBACH, M.D. appears in CMS Medicare data with 1,758 Part D claims and 217 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify GARY FAHRENBACH, M.D.'s credentials?
GARY FAHRENBACH, M.D.'s NPI is 1043303803 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