Diane Ruolin Sun, M.D.
Internal Medicine Physician · Hayward, CA
Diane Ruolin Sun, M.D. is an internal medicine physician with a practice address in Hayward, California, and NPI 1962527952, issued on Mar 20, 2007. Check the license (California C55116, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Diane Ruolin Sun
- Credential
- M.D.
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License numbers
- C55116 CA
0101247713 VA
Self-reported in NPPES; status is on the state search - Practice location
- 27303 Sleepy Hollow Ave S, Hayward, CA 94545
- Phone
- (510) 454-1000
- Enumerated
- Mar 20, 2007
- Record last updated
- Dec 15, 2021 (not updated in 5 years: call before relying on the address or phone)
- Medicaid ID
- 204909105 MO
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 17,696 in California → Look up another NPI →
Also registered at 27303 Sleepy Hollow Ave S
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Diane Ruolin Sun in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license C55116Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
99% fewer Medicare Part D claims than the average internal medicine physician in 2024
16 Medicare Part D claims for 11 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D.
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
Diane Ruolin Sun among 17,696 internal medicine physician records in California
Diane Ruolin Sun, M.D. is one of 17,696 internal medicine physician records with a practice address in California. 79% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2007, is newer than 44% of them.
- NPI issued2007 · 44% of these records are older, 44% newer
- In a Medicare fileYes · 79% of these records are
- In the CMS Doctors and Clinicians fileNo · 63% of these records are
- Record last updated2021 · 61% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207R00000X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
40 internal medicine physician records list a practice address in Hayward
They are 40 of the 3,993 NPPES records with a practice address in Hayward, and 17,696 internal medicine physician records in California.
All 17,696 in California → Every provider in Hayward → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- David Anderson, MDHayward, CA 945451659459410
- Abubakr Asadulla, M.D.Hayward, CA 945451881772648
- Yogesh Bhakta, MDHayward, CA 945451518045376
- Min-Shong Chang, MDHayward, CA 945451063479269
- Allen Chiu, MDHayward, CA 945451316025166
- Gerald Frank, MDHayward, CA 945451124106976
- Neil Handelman, MDHayward, CA 945451528146396
- Kaarel Kaljot, M.D.Hayward, CA 945451275578015
Common questions
What is Diane Ruolin Sun, M.D.'s NPI number?
Diane Ruolin Sun, M.D.'s National Provider Identifier (NPI) is 1962527952, issued on Mar 20, 2007. An NPI identifies a provider in billing; it is not a license.
Where is Diane Ruolin Sun, M.D. located?
The NPPES record lists a practice address at 27303 Sleepy Hollow Ave S, Hayward, CA, 94545. Phone: (510) 454-1000. Providers update this record themselves, so call before visiting.
How can I verify Diane Ruolin Sun, M.D.'s license?
NPPES lists California license number C55116, as entered by the provider. Search the Medical Board of California at https://www.mbc.ca.gov/License-Verification/default.aspx. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Diane Ruolin Sun, M.D. prescribe under Medicare Part D?
In 2024, Diane Ruolin Sun, M.D. had 16 Medicare Part D claims for 11 beneficiaries; the average among internal medicine physician prescribers was 3,176. Part D covers Medicare prescriptions only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.