Cassandra Williams, MD
NPI 1558546820 · Internal Medicine Physician · Amherst, NY
Enrolled with Medicare as Practitioner - Internal Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Cassandra Williams, MD is a Internal Medicine Physician provider in Amherst, NY (NPI 1558546820).
Provider details
- NPI number
- 1558546820
- Entity type
- Individual
- Primary specialty
- Internal Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Female
- Sole proprietor
- No
- License
- 200800022 (NC)
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
18 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
810 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) |
|---|---|---|
| Subsequent Nursing Facility Care With Moderate Level of Medical Decision Making, Per Day, If Using Time, at Least 30 Minutes99309 | 644 | $102 |
| Initial Nursing Facility Care With High Level of Medical Decision Making, Per Day, If Using Time, 50 Minutes Or More99306 | 138 | $171 |
| Advance Care Planning, First 30 Minutes99497 | 16 | $71 |
| Nursing Facility Discharge Management, More Than 30 Minutes99316 | 12 | $113 |
Typical Medicare-allowed amounts for these services range $71–$171 (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 · 252 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Levothyroxine Sodium | 1,190 | 69 |
| Apixabanbrand: Eliquis | 755 | 67 |
| Amlodipine Besylate | 753 | 98 |
| Atorvastatin Calcium | 743 | 107 |
| Furosemide | 697 | 61 |
| Sertraline Hcl | 521 | 49 |
| Duloxetine Hcl |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$232 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
- 2008-01-07
- Last updated
- 2020-10-30
- Certified
- 2020-10-30
Frequently asked questions
- What is Cassandra Williams's NPI number?
- Cassandra Williams's National Provider Identifier (NPI) is 1558546820, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Cassandra Williams's specialty?
- Cassandra Williams is listed in the NPPES registry with a primary specialty of Internal Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is Cassandra Williams located?
- Cassandra Williams's practice location on file with NPPES is 3980a Sheridan Dr Ste 200, Amherst, NY 14226-1741.
- What is Cassandra Williams's phone number?
- The practice phone number listed in the NPPES registry for Cassandra Williams is (716) 309-4772.
- Does Cassandra Williams accept Medicare?
- Cassandra Williams is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Cassandra Williams's NPI active?
- Yes — Cassandra Williams's NPI (1558546820) is active in the NPPES registry as of the last update on 2020-10-30.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.