NPI registry status
Active
2026 NPPES data Nephrology Physician NPI 1366446213 MD
Verify on CMS → William Duff, MD
Nephrology Physician in Louisville, Kentucky.
This profile is drawn from the federal National Provider Identifier Registry (CMS NPPES), which lists more than 7 million U.S. healthcare providers - including 10,569 in Nephrology 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
2K
Medicare Part D claims · 389 beneficiaries · Nephrology Physician avg: 1K
Industry payments
$1.6K
75 payments · CMS Open Payments (Sunshine Act)
Compiled from official public sources by the PlainDoctor editorial team.
What the federal data shows
William Duff, MD filed 2,073 Medicare Part D claims in 2023 as a Nephrology Physician in Louisville, Kentucky.
- 2K
- Part D claims, 2023
- 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.
William Duff, MD's Medicare Part D volume vs every U.S. prescriber
Total Medicare Part D claims, 2023, across all CMS prescribers nationally
2,073 Top 16% higher than 84% of 1,370,886 prescribers
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 certification likely (heuristic, not verified)
William Duff, 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 William Duff, MD?
Quality data not reportedPrimary specialty
Nephrology Physician
Medicare Part D claims
2,073 43% vs specialty avg
Specialty distribution in Kentucky
How Nephrology Physician compares to other specialties among Kentucky 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 Nephrology 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).
William Duff, MD appears in the CMS NPPES registry as a Nephrology Physician provider holding MD credentials at 6400 DUTCHMANS PKWY, Louisville, KY, 40205, with a listed phone of (502) 587-9660. NPI 1366446213 was issued on 06/09/2005.
Medicare Part D records for calendar year 2023 show 2,073 prescription claims written by this provider, covering 389 Medicare beneficiaries and totaling roughly $231K in drug spend, with an opioid prescribing rate of 0.7%.
Nephrology Physician is a mid-sized specialty nationwide, with 10,569 enrolled providers across 55 states and an average of 1,454 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
Provider Details
| NPI | 1366446213 |
|---|---|
| Specialty | Nephrology Physician |
| Credentials | MD |
| Gender | Male |
| NPI Issued | 06/09/2005 |
Hospital and facility affiliations
Facilities where William Duff, 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.
Nephrology Associates OF Kentuckiana Psc
Louisville, KY
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 Duff, MD. Source: openpaymentsdata.cms.gov.
Total received
$1.6K
Largest payer
Boehringer Ingelheim Pharmaceuticals, 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.
Medicare Part D Prescribing Data
CMS Medicare Part D prescriber-level data for calendar year 2023.
2,073
Total Claims
$231K
Total Drug Cost
389
Medicare Beneficiaries
Prescribing Breakdown
- 30-Day Fills
- 5,144
- Total Day Supply
- 152,756
- Generic Drug Cost
- $71K
- Opioid Claims
- 14 (0.7% rate)
- Antibiotic Claims
- 38
Patient Demographics
- Average Patient Age
- 74.3 years
- Avg HCC Risk Score
- 2.77
- Gender Split
- 55% female / 45% male
- Age Distribution
- <65: 51, 65-74: 137, 75-84: 147, 85+: 54
Top Prescribed Drugs (Medicare Part D)
Top drugs by claim count for calendar year 2023. Based on Medicare Part D data only.
What William Duff, MD prescribes most
Top Medicare Part D drugs by claim count, 2023
- Amlodipine Besylate
Amlodipine Besylate
203 claims
- Allopurinol
Allopurinol
160 claims
- Calcitriol
Calcitriol
148 claims
- Losartan Potassium
Losartan Potassium
140 claims
- Furosemide
Furosemide
130 claims
- Torsemide
Torsemide
125 claims
- Hydralazine Hcl
Hydralazine Hcl
116 claims
- Lisinopril
Lisinopril
101 claims
| Drug | Claims |
|---|---|
| Amlodipine Besylate | 203 |
| Allopurinol | 160 |
| Calcitriol | 148 |
| Losartan Potassium | 140 |
| Furosemide | 130 |
| Torsemide | 125 |
| Hydralazine Hcl | 116 |
| Lisinopril | 101 |
| Spironolactone | 71 |
| Hydrochlorothiazide | 42 |
* Counts below 11 are suppressed by CMS for patient privacy. Generic names shown where available from CMS Part D data.
Nephrology Physician Overview
How William Duff, MD fits within the Nephrology Physician landscape nationally.
10,569
Nephrology Physician Providers in US
55
States with Nephrology Physician
1,454
Avg Claims per Provider
William Duff, MD's 2,073 claims are above the specialty average of 1,454.
Nearby Nephrology Physician Providers in Kentucky
Other clinicians with the same primary specialty enrolled in Kentucky, drawn from the same CMS NPPES roster as Duff.
Dr. Shafic Abdul Wahab El Hindi
M.D.
Louisville, KY
Hisham Abu Farsak
Paducah, KY
Dr. Alexander Afanasyev
MD
Louisville, KY
Dr. Sadiq Ahmed
M.D.
Lexington, KY
Dr. Rizwan Akhtar
M.D.
Richmond, KY
Compare Nephrology Physician nationally: see state-by-state distribution →
Before you book an appointment
Use this federal record as your verification checklist, not as a recommendation.
- Confirm the NPI record is current in the official CMS registry, providers update their own NPPES details, and moves can lag. Verify this NPI
- Check the active license and any disciplinary history with the Kentucky medical board, federal registration is not a license check. Credential verification guide
- Weigh a second option: compare this provider with a nearby Nephrology Physician peer on Medicare volume and prescribing patterns. Compare providers
Medicare Part D and MIPS figures describe practice patterns in federal programs only, they are not quality ratings, and PlainDoctor does not rate, rank, or recommend providers.
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Frequently Asked Questions
What is William Duff, MD's specialty? ▼
William Duff, MD specializes in Nephrology Physician and practices in Louisville, Kentucky. Credentials: MD.
How much does William Duff, MD prescribe under Medicare Part D? ▼
In 2023, William Duff, MD wrote 2,073 Medicare Part D claims totaling $231K in drug costs for 389 beneficiaries.
Where is William Duff, MD located? ▼
William Duff, MD is located at 6400 DUTCHMANS PKWY, Louisville, KY, 40205. Phone: (502) 587-9660.
What is William Duff, MD's NPI number? ▼
William Duff, MD's National Provider Identifier (NPI) is 1366446213, issued on 06/09/2005.
Does William Duff, MD prescribe opioids? ▼
Yes, William Duff, MD had 14 opioid claims in 2023 with an opioid prescribing rate of 0.7%.
How many Nephrology Physician providers are there in the US? ▼
There are 10,569 Nephrology Physician providers across 55 states in the US. The average Nephrology Physician provider writes 1,454 Medicare Part D claims per year.
What drugs does William Duff, MD prescribe most often? ▼
Based on 2023 Medicare Part D data, William Duff, MD's most frequently prescribed drugs include Amlodipine Besylate, Allopurinol, Calcitriol. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does William Duff, MD accept Medicare? ▼
William Duff, MD appears in CMS Medicare data with 2,073 Part D claims and 389 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify William Duff, MD's credentials? ▼
William Duff, MD's NPI is 1366446213 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 (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
Compiled from official public sources by the PlainDoctor editorial team.
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.