2026 NPPES data Internal Medicine Physician NPI 1649374109 MD
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Claire Horton, MD

Internal Medicine Physician in Oakland, California. This profile is drawn from the federal National Provider Identifier Registry (CMS NPPES), which lists more than 7 million U.S. healthcare providers - including 172,858 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
749
Medicare Part D claims · 42 beneficiaries · Internal Medicine Physician avg: 3K
Compiled from official public sources by the PlainDoctor editorial team.

What the federal data shows

Claire Horton, MD filed 749 Medicare Part D claims in 2023 as a Internal Medicine Physician in Oakland, California.

749
Part D claims, 2023

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.

Claire Horton, MD's Medicare Part D volume vs every U.S. prescriber

Total Medicare Part D claims, 2023, across all CMS prescribers nationally

749 Top 29% higher than 71% of 1,370,886 prescribers

0–200: 670,926 prescribers (49%). Below this entry. 200–400: 182,923 prescribers (13%). Below this entry. 400–600: 90,619 prescribers (7%). Below this entry. 600–800: 56,224 prescribers (4%). This entry sits in this band. 800–1,000: 40,919 prescribers (3%). Above this entry. 1,000–1,200: 31,827 prescribers (2%). Above this entry. 1,200–1,400: 26,224 prescribers (2%). Above this entry. 1,400–1,600: 21,710 prescribers (2%). Above this entry. 1,600–1,800: 19,072 prescribers (1%). Above this entry. 1,800–2,000: 16,451 prescribers (1%). Above this entry. 2K+: 213,991 prescribers (16%). Above this entry. This provider 0 2K+ every Part D prescriber (claims/yr), bucketed by value

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)

Claire Horton, MD 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 Claire Horton, MD?

Quality data not reported

NPI registry status

Active

Issued 09/12/2006

NPI 1649374109

Primary specialty

Internal Medicine Physician

High-volume

172,858 US NPIs in this specialty

Medicare Part D claims

749 72% vs specialty avg

2023 prescription claims

Specialty avg: 2,716

Specialty distribution in California

How Internal Medicine Physician compares to other specialties among California providers

California providers
Behavior Technician - 17.3%Behavior Technician17.3%Marriage & Family Therapist - 5.5%Marriage & Family Therapist5.5%Student in an Organized Health Care Education/Training Program - 5%Student in an Organized Health Care Education/Training Program5%Mental Health Counselor - 3.9%Mental Health Counselor3.9%Pharmacist - 3.5%Pharmacist3.5%Clinical Social Worker - 3.1%Clinical Social Worker3.1%Internal Medicine Physician - 2.1%Internal Medicine Physician2.1%
Largest specialties in California (% of in-state 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:

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).

Claire Horton, MD appears in the CMS NPPES registry as a Internal Medicine Physician provider holding MD credentials at 3451 E 12TH STREET, Oakland, CA, 94601, with a listed phone of (510) 535-3500. NPI 1649374109 was issued on 09/12/2006. Because NPPES data is self-reported by the provider and refreshed monthly, the address, phone, and specialty reflect what Horton most recently submitted to CMS rather than a vetted directory listing, which is why patients should always confirm the practice is still at this location before scheduling.

Medicare Part D records for calendar year 2023 show 749 prescription claims written by this provider, covering 42 Medicare beneficiaries and totaling roughly $91K in drug spend, with an opioid prescribing rate of 10.9%. These figures capture only Medicare Part D, commercial insurance, Medicaid, and cash-pay prescriptions are not included, and any drug-beneficiary cell under 11 is suppressed by CMS for patient privacy.

Internal Medicine Physician is a high-volume specialty nationwide, with 172,858 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

3451 E 12TH STREET
Oakland, CA 94601

Provider Details

NPI 1649374109
Specialty Internal Medicine Physician
Credentials MD
Gender Female
NPI Issued 09/12/2006

License & disciplinary context - California MBC 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 ~150K California medical licensees in 2023 - they are NOT specific to Claire Horton, MD. To verify Claire Horton, MD's current license status, search the MBC public license lookup directly, or check the Federation of State Medical Boards (FSMB) verification service.

576
Total board actions, California 2023
Across 556 cases
3.84
Actions per 1,000 licensees
California statewide rate
probation
Most common action type
186 cases

MBC 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 California disciplinary trends page. Cross-checked against FSMB U.S. Medical Regulatory Trends.

Medicare Part D Prescribing Data

CMS Medicare Part D prescriber-level data for calendar year 2023.

749
Total Claims
$91K
Total Drug Cost
42
Medicare Beneficiaries

Prescribing Breakdown

30-Day Fills
1,499
Total Day Supply
42,944
Generic Drug Cost
$25K
Opioid Claims
82 (10.9% rate)
Antibiotic Claims
18

Patient Demographics

Average Patient Age
71.9 years
Avg HCC Risk Score
1.56
Gender Split
55% female / 45% male

Top Prescribed Drugs (Medicare Part D)

Top drugs by claim count for calendar year 2023. Based on Medicare Part D data only.

What Claire Horton, MD prescribes most

Top Medicare Part D drugs by claim count, 2023

claims
Source CMS Medicare Part D Prescriber Public Use File As of 2023
Drug Claims
Atorvastatin Calcium
50
Amlodipine Besylate
34
Benazepril Hcl
30
Gabapentin
29
Metformin Hcl
24
Pantoprazole Sodium
24
Clonazepam
22
Levothyroxine Sodium
22
Hydrochlorothiazide
20
Acetaminophen-Codeine
Acetaminophen With Codeine
19

* 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 Claire Horton, MD fits within the Internal Medicine Physician landscape nationally.

172,858
Internal Medicine Physician Providers in US
56
States with Internal Medicine Physician
2,716
Avg Claims per Provider

Claire Horton, MD's 749 claims are below the specialty average of 2,716.

Nearby Internal Medicine Physician Providers in California

Other clinicians with the same primary specialty enrolled in California, drawn from the same CMS NPPES roster as Horton.

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 California 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.

Frequently Asked Questions

What is Claire Horton, MD's specialty?
Claire Horton, MD specializes in Internal Medicine Physician and practices in Oakland, California. Credentials: MD.
How much does Claire Horton, MD prescribe under Medicare Part D?
In 2023, Claire Horton, MD wrote 749 Medicare Part D claims totaling $91K in drug costs for 42 beneficiaries.
Where is Claire Horton, MD located?
Claire Horton, MD is located at 3451 E 12TH STREET, Oakland, CA, 94601. Phone: (510) 535-3500.
What is Claire Horton, MD's NPI number?
Claire Horton, MD's National Provider Identifier (NPI) is 1649374109, issued on 09/12/2006.
Does Claire Horton, MD prescribe opioids?
Yes, Claire Horton, MD had 82 opioid claims in 2023 with an opioid prescribing rate of 10.9%.
How many Internal Medicine Physician providers are there in the US?
There are 172,858 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 Claire Horton, MD prescribe most often?
Based on 2023 Medicare Part D data, Claire Horton, MD's most frequently prescribed drugs include Atorvastatin Calcium, Amlodipine Besylate, Benazepril Hcl. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does Claire Horton, MD accept Medicare?
Claire Horton, MD appears in CMS Medicare data with 749 Part D claims and 42 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify Claire Horton, MD's credentials?
Claire Horton, MD's NPI is 1649374109 with credentials MD. 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

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.