Ann Chen, MD
NPI 1003840307 · Gastroenterology Physician · Stanford, CA
Enrolled with Medicare as Practitioner - Gastroenterology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Ann Chen, MD is a Gastroenterology Physician provider in Stanford, CA (NPI 1003840307).
Provider details
- NPI number
- 1003840307
- Entity type
- Individual
- Primary specialty
- Gastroenterology PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Female
- Sole proprietor
- No
- License
- A76890 (CA)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure28% of score
19 yrs in NPPES registry
- Profile completeness28% of score
100% of core fields populated
- Practice footprint17% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)28% of score
107 Medicare services, 2024 (ranked within specialty)
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 methodology.
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) |
|---|---|---|
| Moderate Sedation Services Provided By the Same Physician Or Other Qualified Health Care Professional Performing a Gastrointestinal Endoscopic Service That Sedation Supports, Requiring the Presence of an Independent Trained Observer to Assist in the MonitoG0500 | 41 | $6 |
| Initial Hospital Care With Straightforward Or Low-Level Medical Decision Making, If Using Time, at Least 55 Minutes99222 | 26 | $147 |
| Biopsy of Large Bowel Using a Flexible Endoscope45380 | 15 | $156 |
| Established Patient Office Or Other Outpatient Visit With Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 14 | $111 |
| Biopsy of Esophagus, Stomach, And/Or Upper Small Bowel Using a Flexible Endoscope43239 | 11 | $107 |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 5 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Omeprazole | 47 | — |
| Entecavir | 17 | — |
| Famotidine | 17 | — |
| Linaclotidebrand: Linzess | 12 | — |
| Peg3350/Sod Sulf,bicarb,cl/Kclbrand: Peg-3350 and Electrolytes | 12 | 12 |
Medicare Part D only. These counts cover prescriptions paid through Medicare Part D in 2024 — they do notinclude cash-pay, commercial-insurance, Medicaid, or Part B–administered drugs, and badly undercount high cash-pay categories (e.g. GLP-1 weight-loss, testosterone, and ED medications). Any drug with 10 or fewer claims is omitted by CMS, and beneficiary counts under 11 are suppressed — so a missing drug means no Part D record, never zero. This is a factual claims summary, not an endorsement, not medical advice, and not a consumer report. Source: CMS Medicare Part D Prescribers — by Provider and Drug.
Practice location
Mailing address
Registry dates
- Enumerated
- 2006-07-10
- Last updated
- 2009-01-10
Frequently asked questions
- What is Ann Chen's NPI number?
- Ann Chen's National Provider Identifier (NPI) is 1003840307, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Ann Chen's specialty?
- Ann Chen is listed in the NPPES registry with a primary specialty of Gastroenterology Physician (Allopathic & Osteopathic Physicians).
- Where is Ann Chen located?
- Ann Chen's practice location on file with NPPES is 300 Pasteur Dr, Stanford, CA 94305-2200.
- What is Ann Chen's phone number?
- The practice phone number listed in the NPPES registry for Ann Chen is (650) 725-3376.
- Does Ann Chen accept Medicare?
- Ann Chen is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Ann Chen's NPI active?
- Yes — Ann Chen's NPI (1003840307) is active in the NPPES registry as of the last update on 2009-01-10.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.