Mark Williams, MD
NPI 1962425819 · Hospitalist Physician · Saint Louis, MO
Enrolled with Medicare as Practitioner - Hospitalist · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Williams, MD is a Hospitalist Physician provider in Saint Louis, MO (NPI 1962425819).
Provider details
- NPI number
- 1962425819
- Entity type
- Individual
- Primary specialty
- Hospitalist PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- 2021045476 (MO)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure28% of score
19 yrs in NPPES registry
- Profile completeness28% of score
100% of core fields populated
- Practice footprint17% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)28% of score
79 Medicare services, 2024 (ranked within specialty)
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 methodology.
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) |
|---|---|---|
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 50 Minutes99233 | 44 | $114 |
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 35 Minutes99232 | 35 | $76 |
Typical Medicare-allowed amounts for these services range $76–$114 (2024). The Medicare-allowed amount is what Medicare recognizes for a service under fee-for-service — a reference figure for 2024, not a price quote and not what you would be billed. Medicare Part B covers roughly an eighth of all NPIs (65+ skew); services with fewer than 11 beneficiaries are suppressed by CMS. Source: CMS Medicare Physician & Other Practitioners, by Provider & Service.
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 1 distinct drug on file.
| Drug | Part D claims (2024) |
|---|---|
| Donepezil Hcl | 11 |
Medicare Part D only. These counts cover prescriptions paid through Medicare Part D in 2024 — they do notinclude cash-pay, commercial-insurance, Medicaid, or Part B–administered drugs, and badly undercount high cash-pay categories (e.g. GLP-1 weight-loss, testosterone, and ED medications). Any drug with 10 or fewer claims is omitted by CMS, and beneficiary counts under 11 are suppressed — so a missing drug means no Part D record, never zero. This is a factual claims summary, not an endorsement, not medical advice, and not a consumer report. Source: CMS Medicare Part D Prescribers — by Provider and Drug.
Practice location
Mailing address
Registry dates
- Enumerated
- 2006-07-25
- Last updated
- 2025-04-17
Frequently asked questions
- What is Mark Williams's NPI number?
- Mark Williams's National Provider Identifier (NPI) is 1962425819, 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 Hospitalist Physician (Allopathic & Osteopathic Physicians).
- Where is Mark Williams located?
- Mark Williams's practice location on file with NPPES is 1 Barnes Jewish Hospital Plz, Saint Louis, MO 63110-1003.
- What is Mark Williams's phone number?
- The practice phone number listed in the NPPES registry for Mark Williams is (314) 362-1700.
- 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 (1962425819) is active in the NPPES registry as of the last update on 2025-04-17.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.