William Bayer, MD
NPI 1528162898 · Endocrinology, Diabetes & Metabolism Physician · Carol Stream, IL
Enrolled with Medicare as Practitioner - Endocrinology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
William Bayer, MD is a Endocrinology, Diabetes & Metabolism Physician provider in Carol Stream, IL (NPI 1528162898).
Provider details
- NPI number
- 1528162898
- Entity type
- Individual
- Primary specialty
- Endocrinology, Diabetes & Metabolism PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- 036077734 (IL)
Specialties & taxonomies
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
1,638 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 | 639 | $135 |
| 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'SG2211 | 413 | $17 |
| Injection of Drug Or Substance Under Skin Or Into Muscle96372 | 168 | $15 |
| Hemoglobin A1c Level83036 | 148 | $10 |
| Continuous Monitoring of Blood Sugar Level in Tissue Fluid Using Sensor Under Skin With Interpretation and Report95251 | 116 | $36 |
| Insertion of Needle Into Vein for Collection of Blood Sample |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 75 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Levothyroxine Sodium | 1,093 | 262 |
| Semaglutidebrand: Ozempic | 565 | 115 |
| Levothyroxine Sodiumbrand: Synthroid | 372 | 92 |
| Metformin Hclbrand: Metformin Hcl Er | 203 | 63 |
| Empagliflozinbrand: Jardiance | 198 | 63 |
| Pen Needle, Diabeticbrand: Nano 2nd Gen Pen Needle |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$1,006 across 17 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
- 2006-09-08
- Last updated
- 2015-03-25
Frequently asked questions
- What is William Bayer's NPI number?
- William Bayer's National Provider Identifier (NPI) is 1528162898, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is William Bayer's specialty?
- William Bayer is listed in the NPPES registry with a primary specialty of Endocrinology, Diabetes & Metabolism Physician (Allopathic & Osteopathic Physicians).
- Where is William Bayer located?
- William Bayer's practice location on file with NPPES is 501 Thornhill Dr, Carol Stream, IL 60188-2793.
- What is William Bayer's phone number?
- The practice phone number listed in the NPPES registry for William Bayer is (630) 668-3210.
- Does William Bayer accept Medicare?
- William Bayer is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is William Bayer's NPI active?
- Yes — William Bayer's NPI (1528162898) is active in the NPPES registry as of the last update on 2015-03-25.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.