NPI registry status
Active
2026 NPPES data Allergy & Immunology Physician NPI 1356321244 DO
Verify on CMS → Charles Frey, DO
Allergy & Immunology Physician in Rockford, 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 3,394 in Allergy & Immunology 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
2K
Medicare Part D claims · 294 beneficiaries · Allergy & Immunology Physician avg: 764
Generic prescribing
80%
generic claims · 20% brand-name · higher generic rates reduce patient out-of-pocket costs
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
Charles Frey, DO filed 1,750 Medicare Part D claims in 2023 as a Allergy & Immunology Physician in Rockford, Illinois, prescribing 80% generic.
- 2K
- Part D claims, 2023
- 80%
- generic prescribing
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.
Charles Frey, DO's Medicare Part D volume vs every U.S. prescriber
Total Medicare Part D claims, 2023, across all CMS prescribers nationally
1,750 Top 17% higher than 83% 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)
Charles Frey, DO 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 Charles Frey, DO?
Quality data not reportedPrimary specialty
Allergy & Immunology Physician
Medicare Part D claims
1,750 129% vs specialty avg
Specialty distribution in Illinois
How Allergy & Immunology 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 Allergy & Immunology 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).
Charles Frey, DO appears in the CMS NPPES registry as an Allergy & Immunology Physician provider holding DO credentials at 698 FEATHERSTONE RD, Rockford, IL, 61107, with a listed phone of (815) 398-3277. NPI 1356321244 was issued on 01/18/2006.
Medicare Part D records for calendar year 2023 show 1,750 prescription claims written by this provider, covering 294 Medicare beneficiaries and totaling roughly $168K in drug spend, split 20% brand-name and 80% generic by claim count.
Allergy & Immunology Physician is a narrow specialty nationwide, with 3,394 enrolled providers across 52 states and an average of 764 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 | 1356321244 |
|---|---|
| Specialty | Allergy & Immunology Physician |
| Credentials | DO |
| Gender | Male |
| NPI Issued | 01/18/2006 |
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 Charles Frey, DO. To verify Charles Frey, DO'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
Charles Frey, DO - brand share 20.0%
Allergy & Immunology Physician average
20% brand-name claims vs 80% generic, on 1,750 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.
1,750
Total Claims
$168K
Total Drug Cost
294
Medicare Beneficiaries
Prescribing Breakdown
- 30-Day Fills
- 3,329
- Total Day Supply
- 95,732
- Brand vs Generic
- 20% brand / 80% generic
- Brand Drug Cost
- $115K
- Generic Drug Cost
- $53K
Patient Demographics
- Average Patient Age
- 71.3 years
- Avg HCC Risk Score
- 0.96
- Gender Split
- 64% female / 36% male
- Age Distribution
- <65: 33, 65-74: 150, 75-84: 98, 85+: 13
Top Prescribed Drugs (Medicare Part D)
Top drugs by claim count for calendar year 2023. Based on Medicare Part D data only.
What Charles Frey, DO prescribes most
Top Medicare Part D drugs by claim count, 2023
- Montelukast Sodium
Montelukast Sodium
427 claims
- Azelastine Hcl
Azelastine Hcl
336 claims
- Fluticasone Propio…
Fluticasone Propionate
289 claims
- Ipratropium Bromide 137
Ipratropium Bromide
137 claims
- Albuterol Sulfate … 105
Albuterol Sulfate Hfa
105 claims
- Advair Diskus 87
Advair Diskus
87 claims
- Flovent Hfa 53
Flovent Hfa
53 claims
- Levocetirizine Dih… 44
Levocetirizine Dihydrochloride
44 claims
| Drug | Claims |
|---|---|
| Montelukast Sodium | 427 |
| Azelastine Hcl | 336 |
| Fluticasone Propionate | 289 |
| Ipratropium Bromide | 137 |
| Albuterol Sulfate Hfa Albuterol Sulfate | 105 |
| Advair Diskus Fluticasone Propion/Salmeterol | 87 |
| Flovent Hfa Fluticasone Propionate | 53 |
| Levocetirizine Dihydrochloride | 44 |
| Wixela Inhub Fluticasone Propion/Salmeterol | 35 |
| Methylprednisolone | 26 |
* Counts below 11 are suppressed by CMS for patient privacy. Generic names shown where available from CMS Part D data.
Allergy & Immunology Physician Overview
How Charles Frey, DO fits within the Allergy & Immunology Physician landscape nationally.
3,394
Allergy & Immunology Physician Providers in US
52
States with Allergy & Immunology Physician
764
Avg Claims per Provider
Charles Frey, DO's 1,750 claims are above the specialty average of 764.
Nearby Allergy & Immunology Physician Providers in Illinois
Other clinicians with the same primary specialty enrolled in Illinois, drawn from the same CMS NPPES roster as Frey.
Dr. Daryn Abraham
M.D.
St Charles, IL
Dr. Justine Ade
MD
Urbana, IL
Dr. Miguel Alcordo
M.D.
Tinley Park, IL
Dr. Ingrid Alexander
MD
Springfield, IL
Dr. Hetal Amin
MD
Channahon, IL
Compare Allergy & Immunology Physician nationally: see state-by-state distribution →
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 Allergy & Immunology 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 Charles Frey, DO's specialty? ▼
Charles Frey, DO specializes in Allergy & Immunology Physician and practices in Rockford, Illinois. Credentials: DO.
How much does Charles Frey, DO prescribe under Medicare Part D? ▼
In 2023, Charles Frey, DO wrote 1,750 Medicare Part D claims totaling $168K in drug costs for 294 beneficiaries.
Where is Charles Frey, DO located? ▼
Charles Frey, DO is located at 698 FEATHERSTONE RD, Rockford, IL, 61107. Phone: (815) 398-3277.
What is Charles Frey, DO's NPI number? ▼
Charles Frey, DO's National Provider Identifier (NPI) is 1356321244, issued on 01/18/2006.
Does Charles Frey, DO prescribe more brand-name or generic drugs? ▼
Charles Frey, DO's prescribing is 20% brand-name and 80% generic drugs by claim count, with $115K in brand drug costs.
How many Allergy & Immunology Physician providers are there in the US? ▼
There are 3,394 Allergy & Immunology Physician providers across 52 states in the US. The average Allergy & Immunology Physician provider writes 764 Medicare Part D claims per year.
What drugs does Charles Frey, DO prescribe most often? ▼
Based on 2023 Medicare Part D data, Charles Frey, DO's most frequently prescribed drugs include Montelukast Sodium, Azelastine Hcl, Fluticasone Propionate. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does Charles Frey, DO accept Medicare? ▼
Charles Frey, DO appears in CMS Medicare data with 1,750 Part D claims and 294 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify Charles Frey, DO's credentials? ▼
Charles Frey, DO's NPI is 1356321244 with credentials DO. 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.
Every figure on PlainDoctor is rendered directly from the federal CMS NPPES registry, Medicare Part D, MIPS, and Open Payments records, no number is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of May 2026.