STEPHEN LOUIS WALSTON MD
NPI 1578887519
Internal Medicine in Mercer Island, WA
About Stephen Louis Walston Md NPPES
Official registry information on file with the National Plan and Provider Enumeration System.
STEPHEN LOUIS WALSTON MD (NPI 1578887519) is an individual internal medicine provider in Mercer Island, Washington, licensed in Washington (MD60423761) and active in the NPI registry since March 2010. He is enrolled in Medicare PECOS, is affiliated with Swedish Medical Center / Cherry Hill, and is a graduate of University Of Texas Medical School At Houston (2010).
NPPES Registry Identity
Specialties & Licenses
Other Identifiers 2
Accepted Insurance
Medicare Participation & PECOS CMS
Medicare enrollment, assignment, billing reassignment, and ordering and referring status from CMS.
Medicare Enrollment Status
Enrolled in Medicare and accepts Medicare assignment
Stephen Louis Walston Md is registered in PECOS and agrees to accept the Medicare-approved amount as full payment. Medicare patients are not billed beyond the standard deductible and coinsurance.
Medicare Billing Reassignments
5Medicare enrollment records show Stephen Walston reassigns Medicare billing to 5 organizations. Each organization bills Medicare for the services this provider delivers there; the nearest is listed first.
Seattle, WA 98104
- Reassigned Medicare billing, Washington enrollment
- 911 clinicians in this Medicare group
Seattle, WA 98104
- Reassigned Medicare billing, Washington enrollment
- 94 clinicians in this Medicare group
Seattle, WA 98104
- Reassigned Medicare billing, Washington enrollment
- 663 clinicians in this Medicare group
Seattle, WA 98104
- Reassigned Medicare billing, Washington enrollment
- 1,270 clinicians in this Medicare group
Seattle, WA 98109
- Reassigned Medicare billing, Washington enrollment
- 2,678 clinicians in this Medicare group
Source: CMS Revalidation Reassignment List, October 2026 release. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.
Areas of Expertise CMS Part B claims 10
Services this provider delivered to Medicare fee-for-service patients, from the CMS Medicare utilization data. Higher counts generally reflect more experience with a service; care delivered outside Medicare is not included.
Hospital Affiliations CMS Care Compare 4
Hospitals where this provider delivers care, identified from recent Medicare claims and place-of-service records.
Swedish Medical Center / Cherry Hill
Acute Care Hospitals · Seattle, WASwedish Medical Center
Acute Care Hospitals · Seattle, WAOverlake Hospital Medical Center
Acute Care Hospitals · Bellevue, WASwedish Issaquah
Acute Care Hospitals · Issaquah, WAPhysician Visit Costs CMS claims · ZIP area
Typical Medicare office-visit costs in the 98040 ZIP code area, from fee-for-service claims. These are area statistics, not this provider’s prices; actual charges vary by service and coverage.
Other Providers at the Same Location NPPES 5
Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.
MERCER ISLAND, WA 98040
Frequently Asked Questions NPPES & CMS
Common questions about this NPI record, answered from the official NPPES registry and CMS datasets shown on this page.
What is Stephen Walston's NPI number?
The NPI number for Stephen Walston is 1578887519. It was assigned to this individual provider in the NPPES registry on March 19, 2010.
Where is Stephen Walston located?
Stephen Walston practices at 3236 78th Ave SE Ste 200, Mercer Island, WA 98040. The listed phone number is (206) 386-9500.
What is Stephen Walston's specialty?
The primary specialty registered for this NPI is Internal Medicine with taxonomy code 207R00000X.
Is Stephen Walston enrolled in Medicare?
Yes. Stephen Walston is registered in the Medicare PECOS system and accepts Medicare assignment, which means accepting the Medicare-approved amount as payment in full for covered services.
Which organizations bill Medicare for Stephen Walston's services?
According to the CMS Revalidation Reassignment List (October 2026 release), Stephen Walston reassigns Medicare benefits to 5 organizations: The Polyclinic (Seattle, WA), King County Finance (Seattle, WA), Swedish Health Services (Seattle, WA), Swedish Health Services (Seattle, WA) and Kaiser Foundation Health Plan Of Washington (Seattle, WA). Each reassignment is filed with Medicare on form CMS-855R, signed by both the clinician and the organization, and lets the organization bill Medicare and receive payment for Stephen Walston's services. Reassignment records can lag staffing changes; confirm current arrangements with the organization.
What insurance does Stephen Walston accept?
Health plans from Ambetter Health, Premera Blue Cross Blue Shield of Alaska and Providence Health Plan list Stephen Walston as in-network in at least one marketplace plan. Coverage varies by plan and year; verify with the insurer or the provider before a visit.
Is Stephen Walston affiliated with any hospitals?
According to CMS data, Stephen Walston is affiliated with Swedish Medical Center / Cherry Hill, Swedish Medical Center, Overlake Hospital Medical Center and Swedish Issaquah.
When was this NPI record last updated?
The NPPES record for Stephen Walston was last updated on November 11, 2021. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 4 years ago. If this record has changed at CMS more recently, you can request an on-demand re-check against the live CMS registry, directly from this page.
# Stephen Louis Walston, MD · NPI 1578887519
Internal Medicine physician in Mercer Island, Washington. Individual provider, active in the CMS NPPES registry since March 19, 2010.
## Identity
- **NPI:** 1578887519 (Entity type: Individual)
- **Enumerated:** March 19, 2010
- **Primary specialty:** Internal Medicine · taxonomy 207R00000X
- **State license:** MD60423761 (Washington)
- **Sole proprietor:** No
## Practice location
- **Address:** 3236 78TH AVE SE STE 200, Mercer Island, WA 98040-3500
- **Phone:** (206) 386-9500 · **Fax:** (206) 386-9605
## Medicare
- **Medicare:** Enrolled (PECOS); accepts Medicare assignment
- **Ordering & referring:** eligible for Part B labs & imaging, durable medical equipment, home health, power mobility devices
- **Bills Medicare through:** 5 organizations under Medicare reassignment (form CMS-855R): The Polyclinic (NPI 1073944039, Seattle, WA); King County Finance (NPI 1306903604, Seattle, WA); Swedish Health Services (NPI 1619680840, Seattle, WA); Swedish Health Services (NPI 1689612954, Seattle, WA); Kaiser Foundation Health Plan Of Washington (NPI 1396810701, Seattle, WA) · CMS Revalidation Reassignment List, October 2026 release
- **Medical school:** University Of Texas Medical School At Houston, class of 2010
## Record status
- **NPPES last updated:** November 11, 2021
- **Other identifiers:** Medicaid 2022131 (WA); Medicaid 1578887519 (WA)
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Source: [NPI Profile](https://npiprofile.com/npi/1578887519) · Data from the CMS NPPES public registry.