Stephen Ma, MD
NPI 1508329442 · Internal Medicine Physician · Stanford, CA
Enrolled with Medicare as Practitioner - Internal Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Stephen Ma, MD is a Internal Medicine Physician provider in Stanford, CA (NPI 1508329442).
Provider details
- NPI number
- 1508329442
- Entity type
- Individual
- Primary specialty
- Internal Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- A177624 (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
7 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
278 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) |
|---|---|---|
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 50 Minutes99233 | 203 | $133 |
| Hospital Discharge Day Management, More Than 30 Minutes99239 | 41 | $131 |
| Initial Hospital Care With Moderate Level of Medical Decision Making, If Using Time, at Least 75 Minutes99223 | 34 | $194 |
Typical Medicare-allowed amounts for these services range $131–$194 (2024). The Medicare-allowed amount is what Medicare recognizes for a service under fee-for-service — a reference figure for 2024, not a price quote and not what you would be billed. Medicare Part B covers roughly an eighth of all NPIs (65+ skew); services with fewer than 11 beneficiaries are suppressed by CMS. Source: CMS Medicare Physician & Other Practitioners, by Provider & Service.
Practice location
Mailing address
Registry dates
- Enumerated
- 2019-04-08
- Last updated
- 2024-07-08
- Certified
- 2024-07-08
Frequently asked questions
- What is Stephen Ma's NPI number?
- Stephen Ma's National Provider Identifier (NPI) is 1508329442, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Stephen Ma's specialty?
- Stephen Ma is listed in the NPPES registry with a primary specialty of Internal Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is Stephen Ma located?
- Stephen Ma's practice location on file with NPPES is 300 Pasteur Dr, Stanford, CA 94305-2200.
- What is Stephen Ma's phone number?
- The practice phone number listed in the NPPES registry for Stephen Ma is (650) 723-4000.
- Does Stephen Ma accept Medicare?
- Stephen Ma is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Stephen Ma's NPI active?
- Yes — Stephen Ma's NPI (1508329442) is active in the NPPES registry as of the last update on 2024-07-08.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.