Marylyn Grondin, M.D.
NPI 1841266327 · Gastroenterology Physician · Portsmouth, NH
Enrolled with Medicare as Practitioner - Gastroenterology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Marylyn Grondin, M.D. is a Gastroenterology Physician provider in Portsmouth, NH (NPI 1841266327).
Provider details
- NPI number
- 1841266327
- Entity type
- Individual
- Primary specialty
- Gastroenterology PhysicianAllopathic & Osteopathic Physicians
- Credential
- M.D.
- Sex
- Female
- Sole proprietor
- No
- License
- 8703 (NH)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure25% of score
20 yrs in NPPES registry
- Profile completeness25% of score
100% of core fields populated
- Practice footprint15% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)25% of score
694 Medicare services, 2024 (ranked within specialty)
- Open Payments transparency10% of score
Has Open Payments disclosures (2024)
Medicare volume is ranked against active providers in the same specialty. 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 .
What this provider does (Medicare)
Based on Medicare fee-for-service claims, 2024; not all care is captured.
| Service (HCPCS) | Medicare services | Typical Medicare-allowed (2024) |
|---|---|---|
| Established Patient Office Or Other Outpatient Visit With Low Level OD Decision Making, If Using Time, 20 Minutes Or More99213 | 213 | $90 |
| Colorectal Cancer Screening; Colonoscopy on Individual at High RiskG0105 | 98 | $178 |
| Biopsy of Esophagus, Stomach, And/Or Upper Small Bowel Using a Flexible Endoscope43239 | 78 | $68 |
| Removal of Polyps Or Growths of Large Bowel Using an Endoscope With Mechanical Snare45385 | 67 | $245 |
| New Patient Office Or Other Outpatient Visit With Low Level of Medical Decision Making, If Using Time, 30 Minutes Or More99203 | 55 | $111 |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 10 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Pantoprazole Sodium | 127 | 44 |
| Omeprazole | 87 | 26 |
| Famotidine | 50 | 15 |
| Linaclotidebrand: Linzess | 35 | — |
| Ondansetronbrand: Ondansetron Odt | 21 | — |
| Dicyclomine Hcl | 17 | — |
| Esomeprazole Magnesium | 17 | — |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$413 across 8 records (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
- 2006-02-24
- Last updated
- 2012-02-13
Frequently asked questions
- What is Marylyn Grondin's NPI number?
- Marylyn Grondin's National Provider Identifier (NPI) is 1841266327, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Marylyn Grondin's specialty?
- Marylyn Grondin is listed in the NPPES registry with a primary specialty of Gastroenterology Physician (Allopathic & Osteopathic Physicians).
- Where is Marylyn Grondin located?
- Marylyn Grondin's practice location on file with NPPES is 330 Borthwick Ave, Portsmouth, NH 03801-4174.
- What is Marylyn Grondin's phone number?
- The practice phone number listed in the NPPES registry for Marylyn Grondin is (603) 433-2488.
- Does Marylyn Grondin accept Medicare?
- Marylyn Grondin is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Marylyn Grondin's NPI active?
- Yes — Marylyn Grondin's NPI (1841266327) is active in the NPPES registry as of the last update on 2012-02-13.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.