Mark Edward Sienko, M.D.

NPI 1932146552ActiveIndividual· Internal Medicine, Medical Oncology· Sequim, WA

Internal Medicine, Medical Oncology (M.D.) in Sequim, Washington, trained at University of Illinois College of Med (Chi/Peor/Rock/Chm-Urb) (class of 1989). Their prescriptions cost Medicare Part D more than their services did: $764,823 for 733 claims, against $36,986 paid for services in 2024. Incyte Corporation was the largest of 3 companies reporting payments in 2025, $375.09 in all, mostly food and beverage.

Overview

NPI	1932146552
Status	Active
Entity type	Individual
Credential	M.D.
Sole proprietor	No
NPI issued	Jun 1, 2006
Last updated in NPPES	Feb 26, 2020
Certified by provider	Feb 26, 2020

Specialties and licenses

Taxonomy	Code	License	State
Internal Medicine, Medical Oncology Primary	207RX0202X	MD00046621	WA
Internal Medicine, Hematology & Oncology	207RH0003X	MD00046621	WA

About license numbers in NPPES

Exclusion screening

List	Result	Details
HHS-OIG LEIE · Nov 10, 2026	No match	Checked by NPI and by name + state
North Carolina Medicaid · Nov 11, 2026	No match	—
New York OMIG · Nov 11, 2026	No match	—
Ohio Medicaid · Nov 11, 2026	No match	—
Pennsylvania Medicheck · Nov 11, 2026	No match	—
Washington HCA · Nov 11, 2026	No match	—

Official OIG search · How matching works ·Bulk check a roster

Medicare

Enrollment (PECOS)	Enrolled Practitioner - Hematology/Oncology (OR); Practitioner - Medical Oncology (WA)
Accepts assignment	Yes (participating)

Medicare services in 2024

Medicare patients	389
Services billed	585 across 6 procedure codes
Paid by Medicare	$36,986

Part D prescriptions in 2024

Prescriptions (claims)	733 · 1,043 30-day fills
Patients	164
Total drug cost	$764,823
Generic share	89% of claims

Medicare sources and data years

Education and affiliations

Medical school	University of Illinois College of Med (Chi/Peor/Rock/Chm-Urb)
Graduation year	1989
Medicare specialty	Medical Oncology
Secondary specialties	Hematology