NPI registry status
Active
2026 NPPES data Geriatric Medicine (Internal Medicine) Physician NPI 1578857835 M.D.
Verify on CMS → Chi Ahn, M.D.
Geriatric Medicine (Internal Medicine) Physician in Chicago, Illinois.
This profile is drawn from the federal National Provider Identifier Registry (CMS NPPES), which lists more than 7 million U.S. healthcare providers - including 4,161 in Geriatric Medicine (Internal Medicine) Physician, and covers specialty classification, practice address, and Medicare Part D prescribing data when reported. According to CMS, every field reflects the provider's official federal registration, see our methodology.
Federal data, no proprietary rating.
We show these CMS records as-is - no composite score, no star rating, no editorial opinion layered on top.
Prescribing volume
650
Medicare Part D claims · 147 beneficiaries · Geriatric Medicine (Internal Medicine) Physician avg: 4K
Generic prescribing
83%
generic claims · 14% brand-name · higher generic rates reduce patient out-of-pocket costs
Industry payments
$24.04
1 payments · CMS Open Payments (Sunshine Act)
Source: CMS Medicare Part D Prescriber Public Use File, 2023
Compiled from official public sources by the PlainDoctor editorial team.
What the federal data shows
Chi Ahn, M.D. filed 650 Medicare Part D claims in 2023 as a Geriatric Medicine (Internal Medicine) Physician in Chicago, Illinois, prescribing 83% generic.
- 650
- Part D claims, 2023
- 83%
- generic prescribing
- $24.04
- industry payments (Sunshine Act)
Every figure on this page comes straight from federal CMS records (NPPES, Medicare Part D, MIPS, Open Payments) - no proprietary rating or editorial opinion is applied.
Chi Ahn, M.D.'s Medicare Part D volume vs every U.S. prescriber
Total Medicare Part D claims, 2023, across all CMS prescribers nationally
650 Top 31% higher than 69% of 1,370,886 prescribers
Each bar is a band; taller bars hold more prescribers. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source CMS Medicare Part D Prescriber Public Use File · 2023
◑
Board-eligible specialty (heuristic, not verified)
Chi Ahn, M.D. practices in an ABMS-board-eligible specialty but we don't have enough CMS-participation signals to confirm active board-certified status. Consult CertificationMatters.org (the official ABMS public lookup).
What does the federal data show about Chi Ahn, M.D.?
Quality data not reportedPrimary specialty
Geriatric Medicine (Internal Medicine) Physician
Medicare Part D claims
650 85% vs specialty avg
Specialty distribution in Illinois
How Geriatric Medicine (Internal Medicine) Physician compares to other specialties among Illinois providers
Board certification
Not published by CMS
CMS does not publish a per-provider board-certification field in NPPES. PlainDoctor does not have a reliable per-specialty certification rate to show for Geriatric Medicine (Internal Medicine) Physician. Verify directly:
How MIPS and board certification work
The Merit-based Incentive Payment System (MIPS) scores providers 0–100 across four performance categories: Quality, Cost, Promoting Interoperability, and Improvement Activities, weighted under 42 CFR §414.1380. Reporting is voluntary for many small practices, so absence of a MIPS score is not a quality signal.
Board certification through an ABMS or AOA member board signals voluntary post-licensure examination plus continuous Maintenance of Certification cycles. Verify any individual provider's status through certificationmatters.org (ABMS) or osteopathic.org (AOA).
Chi Ahn, M.D. appears in the CMS NPPES registry as a Geriatric Medicine (Internal Medicine) Physician provider holding M.D. credentials at 5140 N CALIFORNIA AVE, Chicago, IL, 60625, with a listed phone of (773) 989-7554. NPI 1578857835 was issued on 06/04/2011.
Medicare Part D records for calendar year 2023 show 650 prescription claims written by this provider, covering 147 Medicare beneficiaries and totaling roughly $72K in drug spend, split 14% brand-name and 83% generic by claim count.
Geriatric Medicine (Internal Medicine) Physician is a narrow specialty nationwide, with 4,161 enrolled providers across 52 states and an average of 4,450 Part D claims per prescriber, so the context for interpreting these metrics differs meaningfully from a primary-care baseline.
Important: PlainDoctor is a directory of publicly available government data, not medical advice, a malpractice database, or a quality rating. Inclusion here does not imply a recommendation, and absence of complaints or sanctions on this page does not mean none exist, always verify credentials through the NPPES NPI Registry, your state medical board, and the ABMS or AOA before making healthcare decisions.
Practice Address
Provider Details
| NPI | 1578857835 |
|---|---|
| Specialty | Geriatric Medicine (Internal Medicine) Physician |
| Credentials | M.D. |
| Gender | Male |
| NPI Issued | 06/04/2011 |
Industry payments received (2024) - CMS Open Payments transparency data
The federal Physician Payments Sunshine Act (part of the Affordable Care Act) requires drug and medical-device manufacturers + group purchasing organizations to publicly report payments and other transfers of value to physicians and teaching hospitals. The data below covers 2024 for Chi Ahn, M.D.. Source: openpaymentsdata.cms.gov.
Total received
$24
Largest payer
AIMMUNE THERAPEUTICS, INC.
Most common payment type
Food and Beverage
Industry payments are not necessarily indicators of bias, they include research funding, consulting fees for evidence-based work, royalties for inventions, food at conferences, and similar items. The disclosure exists for transparency. Read our methodology for how we interpret this data.
License & disciplinary context - Illinois IDFPR 2023 annual report
Aggregate state board data only, NOT a determination of any individual provider's status. The figures below describe statewide disciplinary activity across all ~42K Illinois medical licensees in 2023 - they are NOT specific to Chi Ahn, M.D.. To verify Chi Ahn, M.D.'s current license status, search the IDFPR public license lookup directly, or check the Federation of State Medical Boards (FSMB) verification service.
106
Total board actions, Illinois 2023
Across 103 cases
2.52
Actions per 1,000 licensees
Illinois statewide rate
probation
Most common action type
38 cases
IDFPR publishes annual disciplinary statistics as part of public-record reporting under each state's Administrative Procedure Act. See the full breakdown by action type and year on the Illinois disciplinary trends page. Cross-checked against FSMB U.S. Medical Regulatory Trends.
Brand vs generic prescribing mix · Typical
Chi Ahn, M.D. - brand share 14.0%
Geriatric Medicine (Internal Medicine) Physician average
14% brand-name claims vs 83% generic, on 650 2023 Medicare Part D claims.
The federal Medicare Part D Generic Dispensing Rate national benchmark sits near 90% generic / 10% brand for primary-care prescribers, per CMS Office of the Actuary 2024 estimates. Higher brand share is common in specialty prescribing where generic equivalents are not available.
Medicare Part D Prescribing Data
CMS Medicare Part D prescriber-level data for calendar year 2023.
650
Total Claims
$72K
Total Drug Cost
147
Medicare Beneficiaries
Prescribing Breakdown
- 30-Day Fills
- 1,187
- Total Day Supply
- 32,639
- Brand vs Generic
- 14% brand / 83% generic
- Brand Drug Cost
- $59K
- Generic Drug Cost
- $12K
Patient Demographics
- Average Patient Age
- 78.6 years
- Avg HCC Risk Score
- 1.33
- Gender Split
- 67% female / 33% male
Top Prescribed Drugs (Medicare Part D)
Top drugs by claim count for calendar year 2023. Based on Medicare Part D data only.
What Chi Ahn, M.D. prescribes most
Top Medicare Part D drugs by claim count, 2023
- Atorvastatin Calcium
Atorvastatin Calcium
52 claims
- Omeprazole
Omeprazole
44 claims
- Amlodipine Besylate
Amlodipine Besylate
29 claims
- Levothyroxine Sodium
Levothyroxine Sodium
27 claims
- Losartan Potassium
Losartan Potassium
27 claims
- Simvastatin
Simvastatin
26 claims
- Tamsulosin Hcl
Tamsulosin Hcl
21 claims
- Eliquis 19
Eliquis
19 claims
| Drug | Claims |
|---|---|
| Atorvastatin Calcium | 52 |
| Omeprazole | 44 |
| Amlodipine Besylate | 29 |
| Levothyroxine Sodium | 27 |
| Losartan Potassium | 27 |
| Simvastatin | 26 |
| Tamsulosin Hcl | 21 |
| Eliquis Apixaban | 19 |
| Metformin Hcl | 19 |
| Metoprolol Succinate | 18 |
* Counts below 11 are suppressed by CMS for patient privacy. Generic names shown where available from CMS Part D data.
More Geriatric Medicine (Internal Medicine) Physician in IL →
All providers in Illinois →
Compare specialties →
Geriatric Medicine (Internal Medicine) Physician Overview
How Chi Ahn, M.D. fits within the Geriatric Medicine (Internal Medicine) Physician landscape nationally.
4,161
Geriatric Medicine (Internal Medicine) Physician Providers in US
52
States with Geriatric Medicine (Internal Medicine) Physician
4,450
Avg Claims per Provider
Chi Ahn, M.D.'s 650 claims are below the specialty average of 4,450.
Nearby Geriatric Medicine (Internal Medicine) Physician Providers in Illinois
Other clinicians with the same primary specialty enrolled in Illinois, drawn from the same CMS NPPES roster as Ahn.
Before you book an appointment
Use this federal record as your verification checklist, not as a recommendation.
- Confirm the NPI record is current in the official CMS registry, providers update their own NPPES details, and moves can lag. Verify this NPI
- Check the active license and any disciplinary history with the Illinois medical board, federal registration is not a license check. Credential verification guide
- Weigh a second option: compare this provider with a nearby Geriatric Medicine (Internal Medicine) Physician peer on Medicare volume and prescribing patterns. Compare providers
Medicare Part D and MIPS figures describe practice patterns in federal programs only, they are not quality ratings, and PlainDoctor does not rate, rank, or recommend providers.
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Frequently Asked Questions
What is Chi Ahn, M.D.'s specialty? ▼
Chi Ahn, M.D. specializes in Geriatric Medicine (Internal Medicine) Physician and practices in Chicago, Illinois. Credentials: M.D..
How much does Chi Ahn, M.D. prescribe under Medicare Part D? ▼
In 2023, Chi Ahn, M.D. wrote 650 Medicare Part D claims totaling $72K in drug costs for 147 beneficiaries.
Where is Chi Ahn, M.D. located? ▼
Chi Ahn, M.D. is located at 5140 N CALIFORNIA AVE, Chicago, IL, 60625. Phone: (773) 989-7554.
What is Chi Ahn, M.D.'s NPI number? ▼
Chi Ahn, M.D.'s National Provider Identifier (NPI) is 1578857835, issued on 06/04/2011.
Does Chi Ahn, M.D. prescribe more brand-name or generic drugs? ▼
Chi Ahn, M.D.'s prescribing is 14% brand-name and 83% generic drugs by claim count, with $59K in brand drug costs.
How many Geriatric Medicine (Internal Medicine) Physician providers are there in the US? ▼
There are 4,161 Geriatric Medicine (Internal Medicine) Physician providers across 52 states in the US. The average Geriatric Medicine (Internal Medicine) Physician provider writes 4,450 Medicare Part D claims per year.
What drugs does Chi Ahn, M.D. prescribe most often? ▼
Based on 2023 Medicare Part D data, Chi Ahn, M.D.'s most frequently prescribed drugs include Atorvastatin Calcium, Omeprazole, Amlodipine Besylate. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does Chi Ahn, M.D. accept Medicare? ▼
Chi Ahn, M.D. appears in CMS Medicare data with 650 Part D claims and 147 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify Chi Ahn, M.D.'s credentials? ▼
Chi Ahn, M.D.'s NPI is 1578857835 with credentials M.D.. You can verify this through the NPPES NPI Registry, check state medical board records, and confirm board certification through the ABMS or AOA.
Data Sources
View source datasets and methodology notes
- Provider Directory
- CMS National Plan and Provider Enumeration System (NPPES), download.cms.gov/nppes, updated monthly. Contains NPI, specialty, credentials, and practice location.
- Specialty Classification
- NUCC Health Care Provider Taxonomy (nucc.org), the industry standard for classifying provider specialties in Medicare and Medicaid billing.
- Prescribing Data
- CMS Medicare Part D Prescriber Public Use File (2023). Includes claims, drug costs, beneficiaries, and opioid prescribing rates.
- Limitations
- Provider data is self-reported to CMS. Prescribing data reflects Medicare Part D only and does not include commercial insurance, Medicaid, or cash prescriptions. Claims below 11 beneficiaries are suppressed by CMS for privacy.
See our complete data methodology for details on how we collect and process government data.
Data as of April 2026 (NPPES) / 2023 (Medicare Part D). Source: Centers for Medicare & Medicaid Services (CMS).
Disclaimer: Data from CMS NPPES and Medicare Part D. PlainDoctor does not rate or rank providers. Provider information is self-reported and may not be current. Always verify information directly with the provider. About · Methodology
Compiled from official public sources by the PlainDoctor editorial team.