Fidel E. Castillo Diaz, MD
Geriatric Medicine (Internal Medicine) Physician · Chicago, IL
Fidel E. Castillo Diaz, MD is a geriatric medicine (internal medicine) physician with a practice address in Chicago, Illinois, and NPI 1689667347, issued on Aug 29, 2005. Check the license (Illinois 036124066, as entered in NPPES) on the Illinois Department of Financial and Professional Regulation; the Medicare figures below come from public CMS files.
- Name
- Fidel E. Castillo Diaz
- Credential
- MD
- Primary taxonomy
- Geriatric Medicine (Internal Medicine) Physician 207RG0300X
- License number
- 036124066 IL
Self-reported in NPPES; status is on the state search - Practice location
- 840 S Wood St, Chicago, IL 60612
- Phone
- (312) 996-7704
- Enumerated
- Aug 29, 2005
- Record last updated
- Mar 5, 2014 (not updated in 12 years: call before relying on the address or phone)
- Fax
- (312) 413-8283
- Medicare enrollment
- Enrolled (PECOS I20101202000876); accepts Medicare assignment
- Entity
- Type 1 · individual
8 nearest geriatric medicine (internal medicine) physician records → All 179 in Illinois → Look up another NPI →
Also registered at 840 S Wood St
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Fidel E. Castillo Diaz 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 036124066Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
81% fewer Medicare Part D claims than the average geriatric medicine (internal medicine) physician in 2024
787 Medicare Part D claims for 53 beneficiaries, against an average of 4,246 among the 3,116 providers of this specialty who prescribed in Part D. 13 claims were for opioids.
Most prescribed
- Amlodipine Besylate60 claims
- Metformin Hcl39 claims
- Lisinopril36 claims
- Albuterol Sulfate Hfa34 claims
- Omeprazole34 claims
- Losartan Potassium33 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 practice group's MIPS final score for 2023 (Medicare payment program): 87.1 of 100
The Merit-based Incentive Payment System score is reported for the practice group, not for one clinician alone. 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, group reporting; category weights for 2023 (qpp.cms.gov).
Bills Medicare through one group practice
- The Board OF Trustees OF The University OF IllinoisChicago, IL
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Fidel E. Castillo Diaz among 179 geriatric medicine (internal medicine) physician records in Illinois
Fidel E. Castillo Diaz, MD is one of 179 geriatric medicine (internal medicine) physician records with a practice address in Illinois. 71% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2005, is newer than 0% of them.
- NPI issued2005 · 0% of these records are older, 92% newer
- In a Medicare fileYes · 71% of these records are
- In the CMS Doctors and Clinicians fileYes · 42% of these records are
- Graduated1998 · median 1997 among the 76 with a school on file
- Record last updated2014 · 59% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207RG0300X and a Illinois practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Geriatric Medicine (Internal Medicine) Physician providers in Illinois
There are 179 geriatric medicine (internal medicine) physician records in Illinois.
All 179 in Illinois → Every provider in Chicago → Geriatric Medicine (Internal Medicine) Physician nationwide →
The 8 geriatric medicine (internal medicine) physician records with the nearest ZIP codes
- Katya Cruz Madrid, M.DChicago, IL 606121609037498
- Xinqi Dong, M.D.Chicago, IL 606121861440224
- Martin Gorbien, M.D.Chicago, IL 606121477502714
- Nivedita Gunturi, MBBSChicago, IL 606121912240805
- Maria Hansberry, M.D.Chicago, IL 606121710936935
- Donald JurivichChicago, IL 606121184737009
- Snigdha Kola, M.DChicago, IL 606121659621837
- Janice Makela, M.D.Chicago, IL 606121700833738
Common questions
What is Fidel E. Castillo Diaz, MD's NPI number?
Fidel E. Castillo Diaz, MD's National Provider Identifier (NPI) is 1689667347, issued on Aug 29, 2005. An NPI identifies a provider in billing; it is not a license.
Where is Fidel E. Castillo Diaz, MD located?
The NPPES record lists a practice address at 840 S Wood St, Chicago, IL, 60612. Phone: (312) 996-7704. Providers update this record themselves, so call before visiting.
How can I verify Fidel E. Castillo Diaz, MD's license?
NPPES lists Illinois license number 036124066, 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 Fidel E. Castillo Diaz, MD prescribe under Medicare Part D?
In 2024, Fidel E. Castillo Diaz, MD had 787 Medicare Part D claims for 53 beneficiaries; the average among geriatric medicine (internal medicine) physician prescribers was 4,246. Part D covers Medicare prescriptions only.
What is Fidel E. Castillo Diaz, MD's MIPS final score?
The 2023 MIPS final score is 87.1 of 100, reported for the practice group. 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.