Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of October 4, 2026.
NPIDirectory

Dr. Matthew S. Chang, MD

Individual provider Internal Medicine Physician · NPI 1598949521

Dr. Matthew S. Chang, MD practises Gastroenterology in Palo Alto, California. Graduated from University of Michigan Medical School in 2006, 20 years ago. Practices with Permanente Medical Group Inc, a 10,941-clinician group and accepts Medicare assignment. Licensed in California, Massachusetts and New York.

Years since qualifying
20
Trained at
University of Michigan Medical School
Licensed in
CA, MA, NY
In the registry since
2007
Specialties on file
3
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.

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Practice location Address checks out

900 Blake Wilbur Dr
Palo Alto, CA 94304-2201
Phone: (650) 736-5555
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Gastroenterology Physician (primary) Taxonomy 207RG0100X · Licence A133674 (CA)
Internal Medicine Physician Taxonomy 207R00000X · Licence 250090 (MA)
Internal Medicine Physician Taxonomy 207R00000X · Licence 245746 (NY)

Record details

NPI number1598949521
Entity typeIndividual (Type 1)
GenderMale
Credentials MD
Sole proprietorNo
NPI enumeratedDecember 27, 2007
Last updated in NPPESDecember 17, 2021

Medicare enrollment

From the CMS Doctors & Clinicians file — this clinician is enrolled in Medicare.

Medicare specialtyGASTROENTEROLOGY
Medical schoolUNIVERSITY OF MICHIGAN MEDICAL SCHOOL
Graduated 2006 (20 years in practice)
Group practice Permanente Medical Group Inc — 10941 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount

Procedures

From CMS Care Compare, which counts the procedures a clinician billed to Original Medicare and Medicare Advantage over a recent 12-month period. CMS reports a fixed list of common procedures, so this is not everything the clinician does. Counts of 10 or fewer are given as a range, because CMS withholds small numbers.

Colonoscopy 1–10 times
Upper gastrointestinal (GI) endoscopy for acid reflux 1–10 times

The percentile compares how often this clinician performed the procedure with other clinicians who performed it, as CMS calculates it. It measures volume, not outcomes or skill.

Payments from drug and device companies, 2025

Drug and device makers are required by federal law (the Physician Payments Sunshine Act) to report what they pay or give to clinicians, and CMS publishes the reports as Open Payments. This is the 2025 program year. A report is a record of a payment, not an allegation of anything, and many are small items such as meals. Only general payments are listed here; research payments and ownership or investment interests are reported separately by CMS and are not shown.

Food and Beverage $34 1 payment · a meal or drink at a meeting or visit, not a fee

Each amount is the sum of what companies reported for that kind of payment in 2025, rounded to the dollar. Not all of it is income to the clinician: a meal is not a fee, a charitable contribution goes to a charity, and a royalty or an acquisition payment is not a salary.

Check a report, or dispute one, at the source in CMS’s own tool, Open Payments. Corrections go through CMS’s dispute process. This site removes a home address on request and asks for no proof, because that is privacy; it will not remove an accurate payment report on request, because that is a statutory public disclosure.

Colleagues at Permanente Medical Group Inc

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 10941 clinicians in the practice; 12 are shown here.

Other providers in Palo Alto