Mark Williamson, MD
NPI 1760591028 · Psychiatry Physician · Houston, TX
Enrolled with Medicare as Practitioner - Psychiatry · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Williamson, MD is a Psychiatry Physician provider in Houston, TX (NPI 1760591028).
Provider details
- NPI number
- 1760591028
- Entity type
- Individual
- Primary specialty
- Psychiatry PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- H4855 (TX)
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 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
51 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) |
|---|---|---|
| Established Patient Office Or Other Outpatient Visit With Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 51 | $136 |
Typical Medicare-allowed amounts for these services range $136–$136 (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 · 16 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Benztropine Mesylate | 78 | 11 |
| Divalproex Sodiumbrand: Divalproex Sodium Er | 58 | — |
| Lithium Carbonatebrand: Lithium Carbonate Er | 52 | — |
| Olanzapine | 50 | — |
| Paliperidone Palmitatebrand: Invega Sustenna | 30 | — |
| Risperidone | 29 | — |
| Mirtazapine | 28 | — |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$270 across 2 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
- 2006-08-30
- Last updated
- 2019-01-29
Frequently asked questions
- What is Mark Williamson's NPI number?
- Mark Williamson's National Provider Identifier (NPI) is 1760591028, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Mark Williamson's specialty?
- Mark Williamson is listed in the NPPES registry with a primary specialty of Psychiatry Physician (Allopathic & Osteopathic Physicians).
- Where is Mark Williamson located?
- Mark Williamson's practice location on file with NPPES is 5901 Long Dr, Houston, TX 77087-1003.
- What is Mark Williamson's phone number?
- The practice phone number listed in the NPPES registry for Mark Williamson is (713) 970-7000.
- Does Mark Williamson accept Medicare?
- Mark Williamson is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Mark Williamson's NPI active?
- Yes — Mark Williamson's NPI (1760591028) is active in the NPPES registry as of the last update on 2019-01-29.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.