NPI registry status
Active
2026 NPPES data Internal Medicine Physician NPI 1689603151 D.O.
Verify on CMS → Thomas Essex, D.O.
Internal Medicine Physician in Chickasha, Oklahoma.
This profile is drawn from the federal National Provider Identifier Registry (CMS NPPES), which lists more than 7 million U.S. healthcare providers - including 174,792 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
879
Medicare Part D claims · 18 beneficiaries · Internal Medicine Physician avg: 3K
Generic prescribing
96%
generic claims · 4% brand-name · higher generic rates reduce patient out-of-pocket costs
Source: CMS Medicare Part D Prescriber Public Use File, 2024
What the federal data shows
Thomas Essex, D.O. filed 879 Medicare Part D claims in 2024 as an Internal Medicine Physician in Chickasha, Oklahoma, prescribing 96% generic.
- 879
- Part D claims, 2024
- 96%
- generic prescribing
- ≥72nd
- pct by Part D claim volume (lower-bound band)
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.
Federal trust snapshot
What official records show about Thomas Essex, D.O.
Federal records show an active NPI with Medicare Part D prescribing activity — verifiable registry data, not a proprietary rating.
- Verified
NPI registry status
Active listing in the CMS National Provider Identifier Registry (NPI 1689603151), first enumerated 06/30/2006.
Source: CMS NPPES
- Reported
Medicare Part D participation
Filed 879 Medicare Part D prescription claims in the 2023 CMS public use file — indicates active Medicare prescribing participation.
Source: CMS Part D Prescriber PUF
- Reported
Board certification signal
Practices in an ABMS-board-eligible specialty; board certification not confirmed in federal records.
- Not in federal data
Individual sanction lookup
PlainDoctor does not publish per-provider disciplinary determinations. Confirm current license and any individual actions through the state medical board or FSMB verification service.
Source: State medical board / FSMB
This trust snapshot summarizes only what appears in federal CMS/NPPES public records. It is not a composite score, star rating, patient review, or clinical recommendation. PlainDoctor never fabricates reviews or AggregateRating schema.
CMS NPPES provider registry desk
NPI 1689603151 · Internal Medicine Physician
NPI-10 · ENUM-LEGACY · TAX-MEGA · RX-LIGHT · BOOK-LIGHT · PHOTO-ENUM
- NPI-10 1689603151
- ENUM-LEGACY 2006
- TAX-MEGA 175K Internal Medicine
- RX-LIGHT 879
- BOOK-LIGHT 1,347 in Oklahoma
- PHOTO-ENUM Thomas Holmes · 2006
Thomas Essex, D.O.'s Medicare Part D volume vs every U.S. prescriber
Total Medicare Part D claims, 2024, across all CMS prescribers nationally
879 ≥ 72nd percentile 72% of 1,416,883 prescribers are in lower value bands
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.
The percentile is a conservative 100-claim band: it counts only prescribers in lower claim-volume bands. Medicare Part D claim volume is activity context, not a quality measure or recommendation. See methodology § corpus placement.
Source CMS Medicare Part D Prescriber Public Use File · 2024
◑
Board-eligible specialty (heuristic, not verified)
Thomas Essex, D.O. 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 Thomas Essex, D.O.?
Quality data not reportedPrimary specialty
Internal Medicine Physician
Medicare Part D claims
879 68% vs specialty avg
Specialty distribution in Oklahoma
How Internal Medicine Physician compares to other specialties among Oklahoma 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).
Practice Address
Provider Details
| NPI | 1689603151 |
|---|---|
| Specialty | Internal Medicine Physician |
| Credentials | D.O. |
| Gender | Male |
| NPI Issued | 06/30/2006 |
Brand vs generic prescribing mix · Generic-heavy
Thomas Essex, D.O. - brand share 4.0%
Internal Medicine Physician average
4% brand-name claims vs 96% generic, on 879 2024 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 2024.
879
Total Claims
$36K
Total Drug Cost
18
Medicare Beneficiaries
Prescribing Breakdown
- 30-Day Fills
- 881.767
- Total Day Supply
- 23,566
- Brand vs Generic
- 4% brand / 96% generic
- Brand Drug Cost
- $17K
- Generic Drug Cost
- $19K
Patient Demographics
- Average Patient Age
- 55.9 years
- Avg HCC Risk Score
- 0.88
Top Prescribed Drugs (Medicare Part D)
Top drugs by claim count for calendar year 2024. Based on Medicare Part D data only.
What Thomas Essex, D.O. prescribes most
Top Medicare Part D drugs by claim count, 2024
- Lisinopril
Lisinopril
39 claims
- Potassium Chloride
Potassium Chloride
39 claims
- Clonidine Hcl
Clonidine Hcl
36 claims
- Escitalopram Oxalate
Escitalopram Oxalate
31 claims
- Lamotrigine
Lamotrigine
31 claims
- Levothyroxine Sodium
Levothyroxine Sodium
31 claims
- Risperidone
Risperidone
30 claims
- Chlorhexidine Gluc…
Chlorhexidine Gluconate
28 claims
| Drug | Claims |
|---|---|
| Lisinopril | 39 |
| Potassium Chloride | 39 |
| Clonidine Hcl | 36 |
| Escitalopram Oxalate | 31 |
| Lamotrigine | 31 |
| Levothyroxine Sodium | 31 |
| Risperidone | 30 |
| Chlorhexidine Gluconate | 28 |
| Atorvastatin Calcium | 27 |
| Furosemide | 27 |
* 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 Thomas Essex, D.O. fits within the Internal Medicine Physician landscape nationally.
174,792
Internal Medicine Physician Providers in US
56
States with Internal Medicine Physician
2,785
Avg Claims per Provider
Thomas Essex, D.O.'s 879 claims are below the specialty average of 2,785.
Nationwide Internal Medicine Physician peers with similar MIPS or enrollment year
Two federal-record peer sets for Essex, both outside Oklahoma so the neighborhoods are not geographic containment.
Same NPPES enumeration year (2006)
Same-specialty clinicians who entered the NPI registry in the same calendar year, outside this state.
Nearby Internal Medicine Physician Providers in Oklahoma
Other clinicians with the same primary specialty enrolled in Oklahoma, drawn from the same CMS NPPES roster as Essex.
One of 1,347 Internal Medicine Physician providers enrolled in Oklahoma, 5 are shown here.
Abdelrahman Abdalla
Oklahoma City, OK
Dr. Al-Ola Abdallah
M.D
Tulsa, OK
Dr. Tony Abdo
M.D
Oklahoma City, OK
Dr. David Abernethy
M.D.
Oklahoma City, OK
Dr. Ahmed Abou Elmagd
MD
Fort Sill, OK
Compare Internal Medicine Physician nationally: see state-by-state distribution →
Frequently Asked Questions
What is Thomas Essex, D.O.'s specialty? ▼
Thomas Essex, D.O. specializes in Internal Medicine Physician and practices in Chickasha, Oklahoma. Credentials: D.O..
How much does Thomas Essex, D.O. prescribe under Medicare Part D? ▼
In 2024, Thomas Essex, D.O. wrote 879 Medicare Part D claims totaling $36K in drug costs for 18 beneficiaries.
Where is Thomas Essex, D.O. located? ▼
Thomas Essex, D.O. is located at 304 S 29TH ST, Chickasha, OK, 73018. Phone: (405) 896-8058.
What is Thomas Essex, D.O.'s NPI number? ▼
Thomas Essex, D.O.'s National Provider Identifier (NPI) is 1689603151, issued on 06/30/2006.
Does Thomas Essex, D.O. prescribe more brand-name or generic drugs? ▼
Thomas Essex, D.O.'s prescribing is 4% brand-name and 96% generic drugs by claim count, with $17K in brand drug costs.
How many Internal Medicine Physician providers are there in the US? ▼
There are 174,792 Internal Medicine Physician providers across 56 states in the US. The average Internal Medicine Physician provider writes 2,785 Medicare Part D claims per year.
What drugs does Thomas Essex, D.O. prescribe most often? ▼
Based on 2024 Medicare Part D data, Thomas Essex, D.O.'s most frequently prescribed drugs include Lisinopril, Potassium Chloride, Clonidine Hcl. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does Thomas Essex, D.O. accept Medicare? ▼
Thomas Essex, D.O. appears in CMS Medicare data with 879 Part D claims and 18 Medicare beneficiaries in 2024. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify Thomas Essex, D.O.'s credentials? ▼
Thomas Essex, D.O.'s NPI is 1689603151 with credentials D.O.. 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 (2024). 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 August 2026 (NPPES) / 2024 (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
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 August 2026.