Mark Sienko, M.D.
NPI 1932146552 · Medical Oncology Physician · Sequim, WA
Enrolled with Medicare as Practitioner - Medical Oncology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Sienko, M.D. is a Medical Oncology Physician provider in Sequim, WA (NPI 1932146552).
Provider details
- NPI number
- 1932146552
- Entity type
- Individual
- Primary specialty
- Medical Oncology PhysicianAllopathic & Osteopathic Physicians
- Credential
- M.D.
- Sex
- Male
- Sole proprietor
- No
- License
- MD00046621 (WA)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
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
574 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 Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 433 | $95 |
| Established Patient Office Or Other Outpatient Visit With High Level of Medical Decision Making, If Using Time, 40 Minutes Or More99215 | 73 | $139 |
| New Patient Office Or Other Outpatient Visit With a High Level of Medical Decision Making, If Using Time, 60 Minutes Or More99205 | 38 | $177 |
| Established Patient Office Or Other Outpatient Visit With Low Level OD Decision Making, If Using Time, 20 Minutes Or More99213 | 17 | $65 |
| Established Patient Office Or Other Outpatient Visit With Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 13 | $88 |
Typical Medicare-allowed amounts for these services range $65–$177 (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 · 19 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Letrozole | 72 | 23 |
| Dexamethasone | 64 | 16 |
| Prednisone | 51 | 14 |
| Tamoxifen Citrate | 38 | 14 |
| Olanzapine | 32 | — |
| Hydroxyurea | 28 | — |
| Ondansetron Hcl | 26 | 12 |
| Abiraterone Acetate | 22 | — |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$240 across 3 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
- 2006-06-01
- Last updated
- 2020-02-26
- Certified
- 2020-02-26
Frequently asked questions
- What is Mark Sienko's NPI number?
- Mark Sienko's National Provider Identifier (NPI) is 1932146552, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Mark Sienko's specialty?
- Mark Sienko is listed in the NPPES registry with a primary specialty of Medical Oncology Physician (Allopathic & Osteopathic Physicians).
- Where is Mark Sienko located?
- Mark Sienko's practice location on file with NPPES is 844 N 5th Ave, Sequim, WA 98382-3045.
- What is Mark Sienko's phone number?
- The practice phone number listed in the NPPES registry for Mark Sienko is (360) 683-9895.
- Does Mark Sienko accept Medicare?
- Mark Sienko is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Mark Sienko's NPI active?
- Yes — Mark Sienko's NPI (1932146552) is active in the NPPES registry as of the last update on 2020-02-26.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.