NPI registry status
Active
2026 NPPES data Internal Medicine Physician NPI 1639604341 M.D.
Verify on CMS → Ian Guerrero, M.D.
Internal Medicine Physician in Kapolei, Hawaii.
This profile is drawn from the federal National Provider Identifier Registry (CMS NPPES), which lists more than 7 million U.S. healthcare providers - including 172,737 in 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
9K
Medicare Part D claims · 726 beneficiaries · Internal Medicine Physician avg: 3K
Generic prescribing
80%
generic claims · 19% brand-name · higher generic rates reduce patient out-of-pocket costs
Industry payments
$5.0K
188 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
Ian Guerrero, M.D. filed 8,720 Medicare Part D claims in 2023 as a Internal Medicine Physician in Kapolei, Hawaii, prescribing 80% generic.
- 9K
- Part D claims, 2023
- 80%
- generic prescribing
- $5.0K
- 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.
Ian Guerrero, M.D.'s Medicare Part D volume vs every U.S. prescriber
Total Medicare Part D claims, 2023, across all CMS prescribers nationally
8,720 Top 2% higher than 98% 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)
Ian Guerrero, 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 Ian Guerrero, M.D.?
Quality data not reportedPrimary specialty
Internal Medicine Physician
Medicare Part D claims
8,720 221% vs specialty avg
Specialty distribution in Hawaii
How Internal Medicine Physician compares to other specialties among Hawaii 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 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).
Ian Guerrero, M.D. appears in the CMS NPPES registry as an Internal Medicine Physician provider holding M.D. credentials at 91-710 FARRINGTON HWY STE A120, Kapolei, HI, 96707, with a listed phone of (808) 400-3899. NPI 1639604341 was issued on 05/01/2017.
Medicare Part D records for calendar year 2023 show 8,720 prescription claims written by this provider, covering 726 Medicare beneficiaries and totaling roughly $2.6 million in drug spend, split 19% brand-name and 80% generic by claim count, with an opioid prescribing rate of 1.7%.
Internal Medicine Physician is a high-volume specialty nationwide, with 172,737 enrolled providers across 56 states and an average of 2,716 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 | 1639604341 |
|---|---|
| Specialty | Internal Medicine Physician |
| Credentials | M.D. |
| Gender | Male |
| NPI Issued | 05/01/2017 |
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 Ian Guerrero, M.D.. Source: openpaymentsdata.cms.gov.
Total received
$5.0K
Largest payer
Amgen 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.
Brand vs generic prescribing mix · Typical
Ian Guerrero, M.D. - brand share 19.0%
Internal Medicine Physician average
19% brand-name claims vs 80% generic, on 8,720 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.
8,720
Total Claims
$2.6M
Total Drug Cost
726
Medicare Beneficiaries
Prescribing Breakdown
- 30-Day Fills
- 19,852
- Total Day Supply
- 577,776
- Brand vs Generic
- 19% brand / 80% generic
- Brand Drug Cost
- $2.4M
- Generic Drug Cost
- $222K
- Opioid Claims
- 144 (1.7% rate)
- Antibiotic Claims
- 420
Patient Demographics
- Average Patient Age
- 72.9 years
- Avg HCC Risk Score
- 1.47
- Gender Split
- 55% female / 45% male
- Age Distribution
- <65: 81, 65-74: 345, 75-84: 219, 85+: 81
Top Prescribed Drugs (Medicare Part D)
Top drugs by claim count for calendar year 2023. Based on Medicare Part D data only.
What Ian Guerrero, M.D. prescribes most
Top Medicare Part D drugs by claim count, 2023
- Losartan Potassium
Losartan Potassium
624 claims
- Atorvastatin Calcium
Atorvastatin Calcium
590 claims
- Amlodipine Besylate
Amlodipine Besylate
389 claims
- Rosuvastatin Calcium
Rosuvastatin Calcium
309 claims
- Metformin Hcl Er
Metformin Hcl Er
256 claims
- Metoprolol Succinate 218
Metoprolol Succinate
218 claims
- Azithromycin 197
Azithromycin
197 claims
- Tamsulosin Hcl 195
Tamsulosin Hcl
195 claims
| Drug | Claims |
|---|---|
| Losartan Potassium | 624 |
| Atorvastatin Calcium | 590 |
| Amlodipine Besylate | 389 |
| Rosuvastatin Calcium | 309 |
| Metformin Hcl Er Metformin Hcl | 256 |
| Metoprolol Succinate | 218 |
| Azithromycin | 197 |
| Tamsulosin Hcl | 195 |
| Prednisone | 162 |
| Levothyroxine Sodium | 157 |
* Counts below 11 are suppressed by CMS for patient privacy. Generic names shown where available from CMS Part D data.
Internal Medicine Physician Overview
How Ian Guerrero, M.D. fits within the Internal Medicine Physician landscape nationally.
172,737
Internal Medicine Physician Providers in US
56
States with Internal Medicine Physician
2,716
Avg Claims per Provider
Ian Guerrero, M.D.'s 8,720 claims are above the specialty average of 2,716.
Nearby Internal Medicine Physician Providers in Hawaii
Other clinicians with the same primary specialty enrolled in Hawaii, drawn from the same CMS NPPES roster as Guerrero.
Dr. Michael Abdo
M.D.
Ewa Beach, HI
Dr. Carlos Abeyta
MD
Hilo, HI
Dr. Harry Acuna
MD
Waipahu, HI
Dr. Dale Adams
MD
Kailua, HI
Dr. Kevin Adams
MD
Honolulu, HI
Compare Internal Medicine 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 Hawaii medical board, federal registration is not a license check. Credential verification guide
- Weigh a second option: compare this provider with a nearby 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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Medical Specialties Explained
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Understanding Medicare Claims Data
What prescribing data reveals about a provider
In-Network vs Out-of-Network
How insurance networks affect your costs
Telehealth Guide
Virtual care options and coverage in 2026
Explore Hawaii
Frequently Asked Questions
What is Ian Guerrero, M.D.'s specialty? ▼
Ian Guerrero, M.D. specializes in Internal Medicine Physician and practices in Kapolei, Hawaii. Credentials: M.D..
How much does Ian Guerrero, M.D. prescribe under Medicare Part D? ▼
In 2023, Ian Guerrero, M.D. wrote 8,720 Medicare Part D claims totaling $2.6M in drug costs for 726 beneficiaries.
Where is Ian Guerrero, M.D. located? ▼
Ian Guerrero, M.D. is located at 91-710 FARRINGTON HWY STE A120, Kapolei, HI, 96707. Phone: (808) 400-3899.
What is Ian Guerrero, M.D.'s NPI number? ▼
Ian Guerrero, M.D.'s National Provider Identifier (NPI) is 1639604341, issued on 05/01/2017.
Does Ian Guerrero, M.D. prescribe more brand-name or generic drugs? ▼
Ian Guerrero, M.D.'s prescribing is 19% brand-name and 80% generic drugs by claim count, with $2.4M in brand drug costs.
Does Ian Guerrero, M.D. prescribe opioids? ▼
Yes, Ian Guerrero, M.D. had 144 opioid claims in 2023 with an opioid prescribing rate of 1.7%.
How many Internal Medicine Physician providers are there in the US? ▼
There are 172,737 Internal Medicine Physician providers across 56 states in the US. The average Internal Medicine Physician provider writes 2,716 Medicare Part D claims per year.
What drugs does Ian Guerrero, M.D. prescribe most often? ▼
Based on 2023 Medicare Part D data, Ian Guerrero, M.D.'s most frequently prescribed drugs include Losartan Potassium, Atorvastatin Calcium, Amlodipine Besylate. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does Ian Guerrero, M.D. accept Medicare? ▼
Ian Guerrero, M.D. appears in CMS Medicare data with 8,720 Part D claims and 726 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify Ian Guerrero, M.D.'s credentials? ▼
Ian Guerrero, M.D.'s NPI is 1639604341 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.
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.