Mark Williams, MD
NPI 1184653891 · Nephrology Physician · Boston, MA
Enrolled with Medicare as Practitioner - Nephrology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Williams, MD is a Nephrology Physician provider in Boston, MA (NPI 1184653891).
Provider details
- NPI number
- 1184653891
- Entity type
- Individual
- Primary specialty
- Nephrology PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- 45103 (MA)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Other Service Providers
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure25% of score
19 yrs in NPPES registry
- Profile completeness25% of score
100% of core fields populated
- Practice footprint15% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)25% of score
866 Medicare services, 2024 (ranked within specialty)
- Open Payments transparency10% of score
Has Open Payments disclosures (2024)
Medicare volume is ranked against active providers in the same specialty. Signals a provider has no public data for (e.g. Medicare claims) are left out of the score entirely — never counted as zero — so providers without that data are not penalized. See the full formula and weights in our .
What this provider does (Medicare)
Based on Medicare fee-for-service claims, 2024; not all care is captured.
| Service (HCPCS) | Medicare services | Typical Medicare-allowed (2024) |
|---|---|---|
| Hemodialysis Procedure With Physician Evaluation90935 | 281 | $74 |
| Established Patient Office Or Other Outpatient Visit With High Level of Medical Decision Making, If Using Time, 40 Minutes Or More99215 | 127 | $150 |
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 50 Minutes99233 | 104 | $124 |
| Dialysis Services, 4 Or More Physician Visits Per Month (20 Years Or Older)90960 | 73 | $371 |
| Initial Hospital Care With Moderate Level of Medical Decision Making, If Using Time, at Least 75 Minutes99223 | 73 | $181 |
| Visit Complexity Inherent to Evaluation and Management Associated With Medical Care Services That Serve As the Continuing Focal Point for All Needed Health Care Services And/Or With Medical Care Services That Are Part of Ongoing Care Related to a Patient'S |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 27 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Calcitriol | 132 | 38 |
| Irbesartan | 114 | 30 |
| Amlodipine Besylate | 106 | 33 |
| Losartan Potassium | 97 | 32 |
| Finerenonebrand: Kerendia | 86 | 23 |
| Furosemide | 78 | 26 |
| Parenteral Amino Acid 20% No.1brand: Prosol | 71 | — |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$11,421 across 10 records (Open Payments 2024)
Open Payments discloses payments and transfers of value (meals, travel, consulting, research, royalties) from drug and device makers to providers. This is a transparency signal, not a verdict — such payments are legal and common, and their presence is neither an endorsement nor a criticism. Source: CMS Open Payments, program year 2024.
Practice location
Mailing address
Registry dates
- Enumerated
- 2006-07-03
- Last updated
- 2011-04-25
Frequently asked questions
- What is Mark Williams's NPI number?
- Mark Williams's National Provider Identifier (NPI) is 1184653891, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Mark Williams's specialty?
- Mark Williams is listed in the NPPES registry with a primary specialty of Nephrology Physician (Allopathic & Osteopathic Physicians).
- Where is Mark Williams located?
- Mark Williams's practice location on file with NPPES is 1 Joslin Pl, Boston, MA 02215-5306.
- What is Mark Williams's phone number?
- The practice phone number listed in the NPPES registry for Mark Williams is (617) 732-2477.
- Does Mark Williams accept Medicare?
- Mark Williams is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Mark Williams's NPI active?
- Yes — Mark Williams's NPI (1184653891) is active in the NPPES registry as of the last update on 2011-04-25.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.