Mark Williams, PA-C
NPI 1861649642 · Medical Physician Assistant · Berlin, MD
Enrolled with Medicare as Practitioner - Physician Assistant · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Williams, PA-C is a Medical Physician Assistant provider in Berlin, MD (NPI 1861649642).
Provider details
- NPI number
- 1861649642
- Entity type
- Individual
- Primary specialty
- Medical Physician AssistantPhysician Assistants & Advanced Practice Nursing Providers
- Credential
- PA-C
- Sex
- Male
- Sole proprietor
- No
- License
- C0003723 (MD)
Specialties & taxonomies
Physician Assistants & Advanced Practice Nursing Providers
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure28% of score
17 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
452 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) |
|---|---|---|
| Emergency Department Visit With Moderate Level of Medical Decision Making99284 | 217 | $109 |
| Emergency Department Visit With High Level of Medical Decision Making99285 | 171 | $155 |
| Emergency Department Visit With Low Level of Medical Decision Making99283 | 64 | $65 |
Typical Medicare-allowed amounts for these services range $65–$155 (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 · 5 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Cephalexin | 24 | 23 |
| Prednisone | 17 | 17 |
| Hydrocodone/Acetaminophenbrand: Hydrocodone-Acetaminophen | 16 | 16 |
| Ibuprofen | 12 | 11 |
| Methocarbamol | 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
- 2008-08-22
- Last updated
- 2011-09-07
Frequently asked questions
- What is Mark Williams's NPI number?
- Mark Williams's National Provider Identifier (NPI) is 1861649642, 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 Medical Physician Assistant (Physician Assistants & Advanced Practice Nursing Providers).
- Where is Mark Williams located?
- Mark Williams's practice location on file with NPPES is 9714 Healthway Dr # Drl, Berlin, MD 21811-1154.
- What is Mark Williams's phone number?
- The practice phone number listed in the NPPES registry for Mark Williams is (410) 641-3340.
- 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 (1861649642) is active in the NPPES registry as of the last update on 2011-09-07.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.