Mark Northfield, MD
NPI 1861406316 · Orthopaedic Surgery Physician · Petaluma, CA
Enrolled with Medicare as Practitioner - Orthopedic Surgery · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Northfield, MD is a Orthopaedic Surgery Physician provider in Petaluma, CA (NPI 1861406316).
Provider details
- NPI number
- 1861406316
- Entity type
- Individual
- Primary specialty
- Orthopaedic Surgery PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- Yes
- License
- G77114 (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
877 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) |
|---|---|---|
| Established Patient Office Or Other Outpatient Visit With Low Level OD Decision Making, If Using Time, 20 Minutes Or More99213 | 256 | $99 |
| Aspiration And/Or Injection of Fluid From Large Joint20610 | 180 | $77 |
| Established Patient Office Or Other Outpatient Visit With Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 145 | $138 |
| New Patient Office Or Other Outpatient Visit With Moderate Level of Medical Decision Making, If Using Time, 45 Minutes Or More99204 | 115 | $180 |
| X-Ray of Knee, 3 Views73562 | 44 | $46 |
| New Patient Office Or Other Outpatient Visit With Low Level of Medical Decision Making, If Using Time, 30 Minutes Or More |
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 |
|---|---|---|
| Hydrocodone/Acetaminophenbrand: Hydrocodone-Acetaminophen | 90 | 19 |
| Oxycodone Hcl/Acetaminophenbrand: Oxycodone-Acetaminophen | 38 | — |
| Oxycodone Hcl | 26 | — |
| Celecoxib | 21 | — |
| Tramadol Hcl | 13 | — |
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 , 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
- 2006-07-28
- Last updated
- 2021-11-09
- Certified
- 2021-11-09
Frequently asked questions
- What is Mark Northfield's NPI number?
- Mark Northfield's National Provider Identifier (NPI) is 1861406316, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Mark Northfield's specialty?
- Mark Northfield is listed in the NPPES registry with a primary specialty of Orthopaedic Surgery Physician (Allopathic & Osteopathic Physicians).
- Where is Mark Northfield located?
- Mark Northfield's practice location on file with NPPES is 1496 Professional Drive, Petaluma, CA 94954.
- What is Mark Northfield's phone number?
- The practice phone number listed in the NPPES registry for Mark Northfield is (707) 778-1131.
- Does Mark Northfield accept Medicare?
- Mark Northfield is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Mark Northfield's NPI active?
- Yes — Mark Northfield's NPI (1861406316) is active in the NPPES registry as of the last update on 2021-11-09.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.