Gary Maassen, M.D.
NPI 1831170968 · Internal Medicine Physician · Saint Louis, MO
Gary Maassen, M.D. is a Internal Medicine Physician provider in Saint Louis, MO (NPI 1831170968).
Provider details
- NPI number
- 1831170968
- Entity type
- Individual
- Primary specialty
- Internal Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- M.D.
- Sex
- Male
- Sole proprietor
- No
- License
- R7H60 (MO)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure33% of score
20 yrs in NPPES registry
- Profile completeness33% of score
100% of core fields populated
- Practice footprint20% of score
1 documented practice location
- Open Payments transparency13% of score
Has Open Payments disclosures (2024)
Signals a provider has no public data for (e.g. Medicare claims) are left out of the score entirely — never counted as zero — so providers without that data are not penalized. See the full formula and weights in our methodology.
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 64 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Atorvastatin Calcium | 272 | 133 |
| Amlodipine Besylate | 131 | 81 |
| Metoprolol Succinate | 119 | 69 |
| Lisinopril | 115 | 68 |
| Pantoprazole Sodium | 104 | 46 |
| Simvastatin | 91 | 47 |
| Rosuvastatin Calcium |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$16 across 1 record (Open Payments 2024)
Open Payments discloses payments and transfers of value (meals, travel, consulting, research, royalties) from drug and device makers to providers. This is a transparency signal, not a verdict — such payments are legal and common, and their presence is neither an endorsement nor a criticism. Source: CMS Open Payments, program year 2024.
Practice location
Mailing address
Registry dates
- Enumerated
- 2005-11-07
- Last updated
- 2012-09-24
Frequently asked questions
- What is Gary Maassen's NPI number?
- Gary Maassen's National Provider Identifier (NPI) is 1831170968, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Gary Maassen's specialty?
- Gary Maassen is listed in the NPPES registry with a primary specialty of Internal Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is Gary Maassen located?
- Gary Maassen's practice location on file with NPPES is 5034 Griffin Rd, Saint Louis, MO 63128-3418.
- What is Gary Maassen's phone number?
- The practice phone number listed in the NPPES registry for Gary Maassen is (314) 843-7333.
- Is Gary Maassen's NPI active?
- Yes — Gary Maassen's NPI (1831170968) is active in the NPPES registry as of the last update on 2012-09-24.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.