Gemma Guillermo, M.D.
NPI 1831154418 · Psychiatry Physician · Redwood City, CA
Enrolled with Medicare as Practitioner - Psychiatry · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Gemma Guillermo, M.D. is a Psychiatry Physician provider in Redwood City, CA (NPI 1831154418).
Provider details
- NPI number
- 1831154418
- Entity type
- Individual
- Primary specialty
- Psychiatry PhysicianAllopathic & Osteopathic Physicians
- Credential
- M.D.
- Sex
- Female
- Sole proprietor
- Yes
- License
- 61066 (CA)
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
220 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) |
|---|---|---|
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 35 Minutes99232 | 80 | $89 |
| Subsequent Hospital Care With Straightforward Or Low Level of Medical Decision Making, Per Day, If Using Time, at Least 25 Minutes99231 | 74 | $55 |
| Initial Hospital Care With Moderate Level of Medical Decision Making, If Using Time, at Least 75 Minutes99223 | 23 | $196 |
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 50 Minutes99233 | 23 | $134 |
| Hospital Discharge Day Management, More Than 30 Minutes99239 | 20 | $132 |
Typical Medicare-allowed amounts for these services range $55–$196 (2024). The Medicare-allowed amount is what Medicare recognizes for a service under fee-for-service — a reference figure for 2024, 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.
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 1 distinct drug on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Hydroxyzine Hcl | 14 | 14 |
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.
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$476 across 4 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
- 2006-04-18
- Last updated
- 2019-02-13
Frequently asked questions
- What is Gemma Guillermo's NPI number?
- Gemma Guillermo's National Provider Identifier (NPI) is 1831154418, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Gemma Guillermo's specialty?
- Gemma Guillermo is listed in the NPPES registry with a primary specialty of Psychiatry Physician (Allopathic & Osteopathic Physicians).
- Where is Gemma Guillermo located?
- Gemma Guillermo's practice location on file with NPPES is 170 Alameda De Las Pulgas, Redwood City, CA 94062-2799.
- What is Gemma Guillermo's phone number?
- The practice phone number listed in the NPPES registry for Gemma Guillermo is (650) 367-5559.
- Does Gemma Guillermo accept Medicare?
- Gemma Guillermo is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Gemma Guillermo's NPI active?
- Yes — Gemma Guillermo's NPI (1831154418) is active in the NPPES registry as of the last update on 2019-02-13.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.