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DR. DIANE RUOLIN SUN M.D.
NPI 1962527952
Internal Medicine in Hayward, CA

Active since March 20, 2007PECOS Enrolled
27303 SLEEPY HOLLOW AVE S, HAYWARD, CA 94545(510) 454-1000 Get Directions Write a Review

NPPES record last updated: December 15, 2021. Verified against the NPPES registry weekly; last sync: October 25, 2026.

About Dr. Diane Ruolin Sun M.d. NPPES

Official registry information on file with the National Plan and Provider Enumeration System.

DR. DIANE RUOLIN SUN M.D. (NPI 1962527952) is an individual internal medicine provider in Hayward, California, licensed in California (C55116) and active in the NPI registry since March 2007. She is enrolled in Medicare PECOS.

NPPES Registry Identity

NPI1962527952
Entity TypeIndividualFemale
Primary Taxonomy207R00000X
Provider Legal NameDR. DIANE RUOLIN SUNCredential: M.D.
Location Address27303 SLEEPY HOLLOW AVE SHayward, CA 94545-4203
Mailing Address27303 Sleepy Hollow Ave SHayward, CA 94545-4203 · (510) 454-1000
Phone(510) 454-1000
Sole ProprietorNo
Enumeration DateMarch 20, 2007
Last NPPES UpdateDecember 15, 2021
✔ NPI 1962527952 is a valid, active identifier and passes the ISO check-digit test.

Specialties & Licenses 2

★ Primary SpecialtyInternal MedicineAllopathic & Osteopathic Physicians
Taxonomy Code207R00000X
License✔ Licensed in CA · C55116
Definition
A physician who provides long-term, comprehensive care in the office and the hospital, managing both common and complex illness of adolescents, adults and the elderly. Internists are trained in the diagnosis and treatment of cancer, infections and diseases affecting the heart, blood, kidneys, joints and digestive, respiratory and vascular systems. They are also trained in the essentials of primary care internal medicine, which incorporates an understanding of disease prevention, wellness, substance abuse, mental health and effective treatment of common problems of the eyes, ears, skin, nervous system and reproductive organs.
Also ListedStudent in an Organized Health Care Education/Training ProgramTaxonomy 390200000X · License 0101247713 (VA)
27303 SLEEPY HOLLOW AVE S, Hayward, CA 94545
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Other Identifiers 2

Other206012821MO · Regristration
Medicaid204909105MO

Medicare Participation & PECOS CMS

Medicare enrollment, assignment, billing reassignment, and ordering and referring status from CMS.

Medicare Enrollment Status

✔

Enrolled in Medicare (PECOS)

Dr. Diane Ruolin Sun M.d. is registered in the CMS Provider Enrollment, Chain and Ownership System (PECOS).

Eligible to Order & Refer✔ Part B Labs & Imaging✔ Durable Medical Equipment✔ Home Health Agency✔ Power Mobility DevicesPer the CMS Ordering and Referring file. Eligibility means Medicare pays claims that this provider orders or refers for these categories.

Medicare Billing Reassignments

2

Medicare enrollment records show Diane Sun reassigns Medicare billing to 2 organizations. Each organization bills Medicare for the services this provider delivers there; the nearest is listed first.

Permanente Medical Group Inc
12 mi
Internal Medicine
1190 VETERANS BLVD
Redwood City, CA 94063
  • Reassigned Medicare billing, California enrollment
  • 20,078 clinicians in this Medicare group
NPI 1639252604 (650) 299-2000
North East Medical Services
14 mi
Federally Qualified Health Center (FQHC)
35 BAYWOOD AVE
San Mateo, CA 94402
  • Reassigned Medicare billing, California enrollment
  • 176 clinicians in this Medicare group
NPI 1730042904 (888) 500-1886

Source: CMS Revalidation Reassignment List, October 2026 release. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.

Physician Visit Costs CMS claims · ZIP area

Typical Medicare office-visit costs in the 94545 ZIP code area, from fee-for-service claims. These are area statistics, not this provider’s prices; actual charges vary by service and coverage.

New Patient
$153.83 typical visit price
range $69.00 – $202.35
Typical copayment $38.45 (range $17.25 – $50.58)
Most-billed visit code 99204
Established Patient
$119.48 typical visit price
range $23.44 – $166.46
Typical copayment $29.87 (range $5.86 – $41.61)
Most-billed visit code 99214
Amounts reflect what Medicare beneficiaries in this ZIP area are typically charged for office visits. Patients with other coverage should check their individual plans.

Other Providers at the Same Location NPPES 20

Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.

GEORGE LAI M.D.
Internal Medicine (Nephrology)
27303 SLEEPY HOLLOW AVE S
HAYWARD, CA 94545
Alameda County (510) 454-1000
ELAINE K ONG M.D.
Pediatrics
27303 SLEEPY HOLLOW AVE S
HAYWARD, CA 94545
Alameda County (510) 454-1000
DAYNA TAI
Pharmacist
27303 SLEEPY HOLLOW AVE S
HAYWARD, CA 94545
Alameda County (510) 784-4589
RANGASHREE VARADARAJAN MD
Internal Medicine (Nephrology)
27303 SLEEPY HOLLOW AVE S
HAYWARD, CA 94545
Alameda County (510) 784-2769
ARMANDO LASARO PLATA M.D.
Urology
27303 SLEEPY HOLLOW AVE S
HAYWARD, CA 94545
Alameda County (510) 454-1000
LUCY OANH PHUONG M.D.
Pediatrics
27303 SLEEPY HOLLOW AVE S
HAYWARD, CA 94545
Alameda County (510) 454-1000
NATALIE CAC
Allergy & Immunology
27303 SLEEPY HOLLOW AVE S
HAYWARD, CA 94545
Alameda County (510) 784-6225
OLGA LEMBERG MD
Pediatrics
27303 SLEEPY HOLLOW AVE S
HAYWARD, CA 94545
Alameda County (510) 752-1000

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 Diane Sun's NPI number?

The NPI number for Diane Sun is 1962527952. It was assigned to this individual provider in the NPPES registry on March 20, 2007.

Where is Diane Sun located?

Diane Sun practices at 27303 Sleepy Hollow Ave S, Hayward, CA 94545. The listed phone number is (510) 454-1000.

What is Diane Sun's specialty?

The primary specialty registered for this NPI is Internal Medicine with taxonomy code 207R00000X.

Is Diane Sun enrolled in Medicare?

Yes. Diane Sun is registered in the Medicare PECOS enrollment system.

Which organizations bill Medicare for Diane Sun's services?

According to the CMS Revalidation Reassignment List (October 2026 release), Diane Sun reassigns Medicare benefits to 2 organizations: Permanente Medical Group Inc (Redwood City, CA) and North East Medical Services (San Mateo, CA). 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 Diane Sun's services. Reassignment records can lag staffing changes; confirm current arrangements with the organization.

When was this NPI record last updated?

The NPPES record for Diane Sun was last updated on December 15, 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.