William Bayer, MD
Endocrinology, Diabetes & Metabolism Physician · Carol Stream, IL
William Bayer, MD is an endocrinology, diabetes & metabolism physician with a practice address in Carol Stream, Illinois, and NPI 1528162898, issued on Sep 8, 2006. Check the license (Illinois 036077734, as entered in NPPES) on the Illinois Department of Financial and Professional Regulation; the Medicare figures below come from public CMS files.
- Name
- William Bayer
- Credential
- MD
- Primary taxonomy
- Endocrinology, Diabetes & Metabolism Physician 207RE0101X
- License number
- 036077734 IL
Self-reported in NPPES; status is on the state search - Practice location
- 501 Thornhill Dr, Carol Stream, IL 60188
- Phone
- (630) 668-3210
- Enumerated
- Sep 8, 2006
- Record last updated
- Mar 25, 2015 (not updated in 11 years: call before relying on the address or phone)
- Fax
- (630) 668-3505
- Medicaid ID
- 036077734 IL
- Medicare enrollment
- Enrolled (PECOS I20100327000312); accepts Medicare assignment
- Medical or professional school
- Loyola University Of Chicago, Stritch School Of Medicine, 1986
- Telehealth
- Offers telehealth (CMS)
- Entity
- Type 1 · individual
8 nearest endocrinology, diabetes & metabolism physician records → All 436 in Illinois → Look up another NPI →
Also registered at 501 Thornhill Dr
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify William Bayer in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersIllinois Department of Financial and Professional Regulation
Search for license 036077734Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
2.1 times the Medicare Part D claims of the average endocrinology, diabetes & metabolism physician in 2024
5,610 Medicare Part D claims for 757 beneficiaries, against an average of 2,630 among the 8,223 providers of this specialty who prescribed in Part D. Brand-name drugs were 50% of claims.
Most prescribed
- Levothyroxine Sodium1,093 claims
- Ozempic565 claims
- Synthroid372 claims
- Metformin Hcl Er203 claims
- Jardiance198 claims
- Metformin Hcl154 claims
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
The MIPS final score for 2023 (Medicare payment program): 94.1 of 100
The Merit-based Incentive Payment System score is reported for this clinician. Four categories are weighted into the final score; the average among 454,083 clinicians with a measured score was 83.5.
Source: CMS Quality Payment Program, MIPS performance year 2023; category weights for 2023 (qpp.cms.gov).
Industry payments in 2024: $1,005.78
17 payments; by number, the most common kind was food and beverage; the largest payer was Lilly USA, LLC. The 5,661 providers of this specialty with any payment received $5,742.15 on average. Payments are reported by manufacturers, not by the provider, and are not a sign of wrongdoing.
Source: CMS Open Payments, program year 2024 (openpaymentsdata.cms.gov); average among providers of this specialty with at least one payment.
Bills Medicare through one group practice
- Central Dupage Physician GroupWheaton, IL
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
William Bayer among 436 endocrinology, diabetes & metabolism physician records in Illinois
William Bayer, MD is one of 436 endocrinology, diabetes & metabolism physician records with a practice address in Illinois. 85% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2006, is newer than 5% of them.
- NPI issued2006 · 5% of these records are older, 62% newer
- In a Medicare fileYes · 85% of these records are
- In the CMS Doctors and Clinicians fileYes · 68% of these records are
- Graduated1986 · median 2006 among the 295 with a school on file
- Record last updated2015 · 46% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207RE0101X and a Illinois practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Endocrinology, Diabetes & Metabolism Physician providers in Illinois
There are 436 endocrinology, diabetes & metabolism physician records in Illinois.
All 436 in Illinois → Every provider in Carol Stream → Endocrinology, Diabetes & Metabolism Physician nationwide →
The 8 endocrinology, diabetes & metabolism physician records with the nearest ZIP codes
- Aileen WestrickCarol Stream, IL 601881770710493
- Faiza Anjum, MDWheaton, IL 601891235793225
- Adam Stein, MDWheaton, IL 601891316003833
- Lily Agrawal, M.D.Oakbrook Terrace, IL 601811922110394
- Maria Aguilera Astudillo, MDSycamore, IL 601781164040887
- Wendell Malalis, M.D.Sycamore, IL 601781962692418
- Disha Narang, M.D.Evanston, IL 602011235426230
- Hisham Swehli, MBBCHEvanston, IL 602021578242608
Common questions
What is William Bayer, MD's NPI number?
William Bayer, MD's National Provider Identifier (NPI) is 1528162898, issued on Sep 8, 2006. An NPI identifies a provider in billing; it is not a license.
Where is William Bayer, MD located?
The NPPES record lists a practice address at 501 Thornhill Dr, Carol Stream, IL, 60188. Phone: (630) 668-3210. Providers update this record themselves, so call before visiting.
How can I verify William Bayer, MD's license?
NPPES lists Illinois license number 036077734, as entered by the provider. Search the Illinois Department of Financial and Professional Regulation at https://idfpr.illinois.gov/checklicense.html. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does William Bayer, MD prescribe under Medicare Part D?
In 2024, William Bayer, MD had 5,610 Medicare Part D claims for 757 beneficiaries; the average among endocrinology, diabetes & metabolism physician prescribers was 2,630. Part D covers Medicare prescriptions only.
What is William Bayer, MD's MIPS final score?
The 2023 MIPS final score is 94.1 of 100. The average among 454,083 clinicians with a measured score was 83.5.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.