NPI registry status
Active
2026 NPPES data Rheumatology Physician NPI 1477536498 M.D.
Verify on CMS → William Matos-Santiago, M.D.
Rheumatology Physician in San Juan, Puerto Rico.
This profile is drawn from the federal National Provider Identifier Registry (CMS NPPES), which lists more than 7 million U.S. healthcare providers - including 6,181 in Rheumatology 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
7K
Medicare Part D claims · 622 beneficiaries · Rheumatology Physician avg: 2K
Generic prescribing
83%
generic claims · 17% brand-name · higher generic rates reduce patient out-of-pocket costs
Industry payments
$53.35
3 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
William Matos-Santiago, M.D. filed 6,611 Medicare Part D claims in 2023 as a Rheumatology Physician in San Juan, Puerto Rico, prescribing 83% generic.
- 7K
- Part D claims, 2023
- 83%
- generic prescribing
- $53.35
- 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.
William Matos-Santiago, M.D.'s Medicare Part D volume vs every U.S. prescriber
Total Medicare Part D claims, 2023, across all CMS prescribers nationally
6,611 Top 4% higher than 96% 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)
William Matos-Santiago, 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 William Matos-Santiago, M.D.?
Quality data not reportedPrimary specialty
Rheumatology Physician
Medicare Part D claims
6,611 222% vs specialty avg
Specialty distribution in Puerto Rico
How Rheumatology Physician compares to other specialties among Puerto Rico 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 Rheumatology 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).
William Matos-Santiago, M.D. appears in the CMS NPPES registry as a Rheumatology Physician provider holding M.D. credentials at LA TORRE DE PLAZA LAS AMERICAS, San Juan, PR, 00918, with a listed phone of (787) 756-7730. NPI 1477536498 was issued on 11/23/2005.
Medicare Part D records for calendar year 2023 show 6,611 prescription claims written by this provider, covering 622 Medicare beneficiaries and totaling roughly $6.0 million in drug spend, split 17% brand-name and 83% generic by claim count, with an opioid prescribing rate of 0.7%.
Rheumatology Physician is a mid-sized specialty nationwide, with 6,181 enrolled providers across 52 states and an average of 2,054 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 | 1477536498 |
|---|---|
| Specialty | Rheumatology Physician |
| Credentials | M.D. |
| Gender | Male |
| NPI Issued | 11/23/2005 |
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 William Matos-Santiago, M.D.. Source: openpaymentsdata.cms.gov.
Total received
$53
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
William Matos-Santiago, M.D. - brand share 17.0%
Rheumatology Physician average
17% brand-name claims vs 83% generic, on 6,611 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.
6,611
Total Claims
$6.0M
Total Drug Cost
622
Medicare Beneficiaries
Prescribing Breakdown
- 30-Day Fills
- 7,580
- Total Day Supply
- 220,244
- Brand vs Generic
- 17% brand / 83% generic
- Brand Drug Cost
- $5.9M
- Generic Drug Cost
- $99K
- Opioid Claims
- 46 (0.7% rate)
- Antibiotic Claims
- 24
Patient Demographics
- Average Patient Age
- 71.8 years
- Avg HCC Risk Score
- 1.53
- Gender Split
- 81% female / 19% male
- Age Distribution
- <65: 101, 65-74: 273, 75-84: 204, 85+: 44
Top Prescribed Drugs (Medicare Part D)
Top drugs by claim count for calendar year 2023. Based on Medicare Part D data only.
What William Matos-Santiago, M.D. prescribes most
Top Medicare Part D drugs by claim count, 2023
- Methotrexate
Methotrexate
1,138 claims
- Diclofenac Sodium
Diclofenac Sodium
860 claims
- Humira(Cf) Pen 387
Humira(Cf) Pen
387 claims
- Sulindac 380
Sulindac
380 claims
- Gabapentin 316
Gabapentin
316 claims
- Alendronate Sodium 270
Alendronate Sodium
270 claims
- Ibandronate Sodium 215
Ibandronate Sodium
215 claims
- Enbrel Sureclick 186
Enbrel Sureclick
186 claims
| Drug | Claims |
|---|---|
| Methotrexate Methotrexate Sodium | 1,138 |
| Diclofenac Sodium | 860 |
| Humira(Cf) Pen Adalimumab | 387 |
| Sulindac | 380 |
| Gabapentin | 316 |
| Alendronate Sodium | 270 |
| Ibandronate Sodium | 215 |
| Enbrel Sureclick Etanercept | 186 |
| Synthroid Levothyroxine Sodium | 180 |
| Meloxicam | 128 |
* Counts below 11 are suppressed by CMS for patient privacy. Generic names shown where available from CMS Part D data.
Rheumatology Physician Overview
How William Matos-Santiago, M.D. fits within the Rheumatology Physician landscape nationally.
6,181
Rheumatology Physician Providers in US
52
States with Rheumatology Physician
2,054
Avg Claims per Provider
William Matos-Santiago, M.D.'s 6,611 claims are above the specialty average of 2,054.
Nearby Rheumatology Physician Providers in Puerto Rico
Other clinicians with the same primary specialty enrolled in Puerto Rico, drawn from the same CMS NPPES roster as Matos-Santiago.
Dr. Paloma Alejandro
M.D.
San Juan, PR
Dr. Roberto Alvarez
M.D.
Aibonito, PR
Dr. Osvaldo Antommattei
MD
Ponce, PR
Dr. Oscar Arill
M.D.
San Juan, PR
Dr. Michael Babilonia Roman
M.D.
Mayaguez, PR
Compare Rheumatology 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 Puerto Rico medical board, federal registration is not a license check. Credential verification guide
- Weigh a second option: compare this provider with a nearby Rheumatology 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
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How insurance networks affect your costs
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Virtual care options and coverage in 2026
Explore Puerto Rico
Frequently Asked Questions
What is William Matos-Santiago, M.D.'s specialty? ▼
William Matos-Santiago, M.D. specializes in Rheumatology Physician and practices in San Juan, Puerto Rico. Credentials: M.D..
How much does William Matos-Santiago, M.D. prescribe under Medicare Part D? ▼
In 2023, William Matos-Santiago, M.D. wrote 6,611 Medicare Part D claims totaling $6.0M in drug costs for 622 beneficiaries.
Where is William Matos-Santiago, M.D. located? ▼
William Matos-Santiago, M.D. is located at LA TORRE DE PLAZA LAS AMERICAS, San Juan, PR, 00918. Phone: (787) 756-7730.
What is William Matos-Santiago, M.D.'s NPI number? ▼
William Matos-Santiago, M.D.'s National Provider Identifier (NPI) is 1477536498, issued on 11/23/2005.
Does William Matos-Santiago, M.D. prescribe more brand-name or generic drugs? ▼
William Matos-Santiago, M.D.'s prescribing is 17% brand-name and 83% generic drugs by claim count, with $5.9M in brand drug costs.
Does William Matos-Santiago, M.D. prescribe opioids? ▼
Yes, William Matos-Santiago, M.D. had 46 opioid claims in 2023 with an opioid prescribing rate of 0.7%.
How many Rheumatology Physician providers are there in the US? ▼
There are 6,181 Rheumatology Physician providers across 52 states in the US. The average Rheumatology Physician provider writes 2,054 Medicare Part D claims per year.
What drugs does William Matos-Santiago, M.D. prescribe most often? ▼
Based on 2023 Medicare Part D data, William Matos-Santiago, M.D.'s most frequently prescribed drugs include Methotrexate, Diclofenac Sodium, Humira(Cf) Pen. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does William Matos-Santiago, M.D. accept Medicare? ▼
William Matos-Santiago, M.D. appears in CMS Medicare data with 6,611 Part D claims and 622 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify William Matos-Santiago, M.D.'s credentials? ▼
William Matos-Santiago, M.D.'s NPI is 1477536498 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.