Rex L. Mahnensmith, M.D.
Internal Medicine Physician · Waterbury, CT
Rex L. Mahnensmith, M.D. is an internal medicine physician with a practice address in Waterbury, Connecticut, and NPI 1760466528, issued on Dec 5, 2005. Check the license (Connecticut 021731, as entered in NPPES) on the Connecticut Medical Examining Board; the Medicare figures below come from public CMS files.
- Name
- Rex L. Mahnensmith
- Credential
- M.D.
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- 021731 CT
Self-reported in NPPES; status is on the state search - Practice location
- 80 Phoenix Ave, Waterbury, CT 06702
- Phone
- (203) 756-8021
- Enumerated
- Dec 5, 2005
- Record last updated
- Oct 22, 2015 (not updated in 11 years: call before relying on the address or phone)
- Fax
- (203) 596-9038
- Medicaid ID
- 001217314 CT
- Medicare enrollment
- Enrolled (PECOS I20100830000814); accepts Medicare assignment
- Medical or professional school
- Yale University School Of Medicine, 1977
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 2,623 in Connecticut → Look up another NPI →
Also registered at 80 Phoenix Ave
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Rex L. Mahnensmith in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersConnecticut Medical Examining Board
Search for license 021731Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
11% fewer Medicare Part D claims than the average internal medicine physician in 2024
2,837 Medicare Part D claims for 223 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D. Brand-name drugs were 14% of claims. 12 claims were for opioids.
Most prescribed
- Albuterol Sulfate Hfa86 claims
- Amlodipine Besylate84 claims
- Prednisone82 claims
- Atorvastatin Calcium71 claims
- Diclofenac Sodium63 claims
- Gabapentin62 claims
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
Industry payments in 2024: $481.92
25 payments; by number, the most common kind was food and beverage; the largest payer was AstraZeneca Pharmaceuticals LP. The 50,334 providers of this specialty with any payment received $1,303.06 on average. Payments are reported by manufacturers, not by the provider, and are not a sign of wrongdoing.
Source: CMS Open Payments, program year 2024 (openpaymentsdata.cms.gov); average among providers of this specialty with at least one payment.
Bills Medicare through 2 group practices
- CT Medical Group Inc.Orange, CT
- Docs Medical IncBethel, CT
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Rex L. Mahnensmith among 2,623 internal medicine physician records in Connecticut
Rex L. Mahnensmith, M.D. is one of 2,623 internal medicine physician records with a practice address in Connecticut. 81% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2005, is newer than 0% of them.
- NPI issued2005 · 0% of these records are older, 89% newer
- In a Medicare fileYes · 81% of these records are
- In the CMS Doctors and Clinicians fileYes · 63% of these records are
- Graduated1977 · median 2004 among the 1,646 with a school on file
- Record last updated2015 · 61% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207R00000X and a Connecticut practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
119 internal medicine physician records list a practice address in Waterbury
They are 119 of the 3,148 NPPES records with a practice address in Waterbury, and 2,623 internal medicine physician records in Connecticut.
All 2,623 in Connecticut → Every provider in Waterbury → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Florymar Alvarez, MDWaterbury, CT 067021811419377
- Edgar Catala, MDWaterbury, CT 067021053369819
- Sunil D'Cunha, MDWaterbury, CT 067021396746160
- Elie Helou, MDWaterbury, CT 067021912252115
- Zife Krosi, MDWaterbury, CT 067021881695070
- Tess Lombard, MDWaterbury, CT 067021710999198
- Stephen Rossner, M.D.Waterbury, CT 067021144250739
- Akua Sam, MDWaterbury, CT 067021568454635
Common questions
What is Rex L. Mahnensmith, M.D.'s NPI number?
Rex L. Mahnensmith, M.D.'s National Provider Identifier (NPI) is 1760466528, issued on Dec 5, 2005. An NPI identifies a provider in billing; it is not a license.
Where is Rex L. Mahnensmith, M.D. located?
The NPPES record lists a practice address at 80 Phoenix Ave, Waterbury, CT, 06702. Phone: (203) 756-8021. Providers update this record themselves, so call before visiting.
How can I verify Rex L. Mahnensmith, M.D.'s license?
NPPES lists Connecticut license number 021731, as entered by the provider. Search the Connecticut Medical Examining Board at https://www.elicense.ct.gov/Lookup/LicenseLookup.aspx. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Rex L. Mahnensmith, M.D. prescribe under Medicare Part D?
In 2024, Rex L. Mahnensmith, M.D. had 2,837 Medicare Part D claims for 223 beneficiaries; the average among internal medicine physician prescribers was 3,176. Part D covers Medicare prescriptions only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.