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Dr. Gregory A. Marshall, MD
NPI1437237526
- Part D claims, 2020
- 181
- Publications
- 3
- Hospital affiliations
- 3
- Industry payments
- $596
- Medical group
- 1
- Practice address
- 1601 Ygnacio Valley Rd, Walnut Creek, CA 94598
- Practice phone
- Call (925) 939-3000
- Professional email
- Get professional email
- Personal email
- Get personal email
- Mobile number
- Get mobile number
Primary practice
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Dr. Gregory A. Marshall is a urologist in Walnut Creek, California
Dr. Marshall practices at John Muir Medical Center, Walnut Creek in Walnut Creek, California, part of John Muir Health.
Dr. Marshall's NPI, 1437237526, was assigned on November 2, 2006. Dr. Marshall graduated from Keck School of Medicine of USC in 1987. Dr. Marshall holds California license G65068.
NPI and contact details
- NPI
- 1437237526NPI Registry (opens in a new tab)
- NPI enumeration date
- November 2, 2006
- NPI status
- Active
- Practice phone
- (925) 939-3000
- Professional email
- Get email
- Personal email
- Get email
- Mobile number
- Get number
- Sex
- Male
- Medical school graduation
- 1987
Sources: NPPES NPI Registry (CMS); Dmand AI Professional Profile Data; and Dmand AI Affiliation Data
Dr. Gregory A. Marshall practices at John Muir Medical Center, Walnut Creek in Walnut Creek, California
Dr. Marshall's primary practice is John Muir Medical Center, Walnut Creek, at 1601 Ygnacio Valley Rd, Walnut Creek, CA 94598 in Contra Costa County. The practice phone is (925) 939-3000.
- John Muir Medical Center, Walnut Creek1601 Ygnacio Valley Rd, Walnut Creek, CA 94598 · Contra Costa CountyPhone(925) 939-3000
Source: Dmand AI Affiliation Data
Dr. Gregory A. Marshall is affiliated with 3 sites of care and 1 medical group
Dr. Marshall's primary practice is John Muir Medical Center, Walnut Creek in Walnut Creek, California, part of John Muir Health. Dr. Marshall is also affiliated with Walnut Creek Medical Center. The medical group on file is The Permanente Medical Group, Inc. Dmand AI also links Dr. Marshall to 1 more hospital, named with a free account.
Sources: Dmand AI Affiliation Data; and Dmand AI Org Hierarchy Data
Dmand AI tracks the EHR system at Dr. Gregory A. Marshall's practice
Dmand AI tracks the electronic health record (EHR) system at each site where Dr. Marshall practices, 3 sites in all. Vendor and product names are available with a free account.
| Site | EHR vendor and product |
|---|---|
| John Muir Medical Center, Walnut Creek | Available with a free account |
| +2 more affiliated sites | Available with a free account |
Source: Dmand AI Technology Install Data
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Dr. Gregory A. Marshall is one of 1,395 urologists in California
Urology is Dr. Marshall's primary specialty in the NPI Registry, under taxonomy code 208800000X. Dr. Marshall is board certified in urology by the American Board of Urology. Dr. Marshall is licensed in California.
Specialties and state licenses
- Urology, CaliforniaPrimary
Urologists near Dr. Marshall
Counts of urologists with a Dmand AI profile, by place and practice. Each opens the list.
1,395urologists in California13urologists in Walnut Creek2urologists at John Muir Medical Center, Walnut Creek
Sources: NPPES NPI Registry (CMS); Dmand AI Professional Profile Data; and Dmand AI Peer Benchmarks
Dr. Gregory A. Marshall's patients have a median age of 72
Across all payers, Dmand AI patient panel data puts Dr. Marshall's median patient age at 72, with 0% women.
Dr. Marshall's patients across all payers
Dmand AI patient panel data covers Medicare, Medicaid and commercial patients.
Patient panel by age, all payers
Median age 72
Patient panel by sex, all payers
- Women0%
- Men97%
Source: Dmand AI Patient Panel Data
Dr. Gregory A. Marshall wrote 181 Medicare Part D claims in 2020
In 2020, Dr. Marshall wrote 181 Medicare Part D claims. Every claim was for a generic drug. They cover 6 drugs, with $5,732 in total drug cost. In 2019, CMS named 567 claims across 12 drugs.
Part D claims, 2020181
Drugs named by CMS6
Total drug cost$5,732
Dr. Marshall's most prescribed drugs by claims, 2020
CMS names a drug when it has 11 or more claims. Share is of the claims for drugs CMS names.
Part D claims for drugs CMS names, 2019 to 2020
- 2019
- 2020
- Claims for drugs CMS names
- 2019: 5672020: 18168%
Drugs named by CMS: 6 in 2020, 12 in 2019.
Source: Medicare Part D Prescribers - by Provider and Drug (CMS), 2024 data, released May 6, 2026
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Dr. Gregory A. Marshall has 3 publications on record
Dmand AI links 3 papers to Dr. Marshall. Dr. Marshall has published most often in J Urol. Dr. Marshall's most frequent co-authors are Peter R. Carroll, MD and Gary S. Nicolaisen, MD.
Papers3
Dr. Marshall's most frequent co-authors
Recent publications by Dr. Marshall
J Urol
ContusionsHematuriaKidney
ArteriesBlood Flow VelocityErectile Dysfunction
See who Dr. Marshall researches with
Physician Network Discovery turns co-authorship, shared hospitals and shared groups into a map of who Dr. Marshall works with, so you can find a warm path to the right urologists.
Sources: PubMed (National Library of Medicine); and Dmand AI Research Linkage
Dr. Gregory A. Marshall received $596 in industry payments from 2018 to 2025
CMS Open Payments shows 6 general payments to Dr. Marshall from 3 drug and device companies from 2018 to 2025. Gifts make up the largest share, 58% of the total. Intuitive Surgical, Inc. paid the most, $513.
General payments to Dr. Marshall by program year, 2018 to 2025
General payments to Dr. Marshall by kind, 2018 to 2025
$596in total
- Gifts$34458%
- Food and beverage$25242%
Companies that paid Dr. Marshall the most, 2018 to 2025
Share is of all general payments to this clinician.
Source: Open Payments (CMS), 2025 data, released July 7, 2026
Dr. Gregory A. Marshall has 1 award and honors on record
Dmand AI lists 1 award for Dr. Marshall, most recently CMS Stage 1 2012 in 2011.
Awards and honors for Dr. Marshall
- 2011
- CMS Stage 1 2012
Source: Dmand AI Professional Profile Data
Dr. Gregory A. Marshall graduated from Keck School of Medicine of USC
Dr. Marshall graduated from Keck School of Medicine of USC in 1987.
- Medical school
- Board certified in urology
Source: Dmand AI Professional Profile Data
Sources for Dr. Gregory A. Marshall's profile data
| Data on this page | Source |
|---|---|
| NPI, name, sex, specialty and licenses | NPPES NPI Registry (CMS) (opens in a new tab)Dmand AI Professional Profile Data |
| Practice locations and phone | Dmand AI Affiliation Data |
| Primary practice, affiliations and health system | Dmand AI Affiliation DataDmand AI Org Hierarchy Data |
| Medicare patients and the all-payer patient panel | Dmand AI Patient Panel Data |
| Part D prescribing | Medicare Part D Prescribers - by Provider and Drug (CMS) (opens in a new tab) |
| Publications, topics and co-authors | PubMed (National Library of Medicine) (opens in a new tab)Dmand AI Research Linkage |
| Industry payments | Open Payments (CMS) (opens in a new tab) |
| Awards and committee roles | Dmand AI Professional Profile Data |
| Training, board certification and memberships | Dmand AI Professional Profile Data |
| EHR at each practice site | Dmand AI Technology Install Data |
| Similar physicians | Dmand AI Affiliation Data |
Data last refreshed October 2026Report an inaccuracyRemove my information
FAQ
Frequently asked questions about Dr. Gregory A. Marshall
Spotted something out of date? Email hello@dmand.ai and we will check the record. Contact details live in the free trial.
What is Dr. Gregory A. Marshall's NPI number?
Dr. Gregory A. Marshall's NPI number is 1437237526. It was assigned on November 2, 2006, and it is active in the NPI Registry.
What kind of doctor is Dr. Gregory A. Marshall?
Dr. Gregory A. Marshall is a urologist in Walnut Creek, California. The primary specialty in the NPI Registry is Urology Physician (taxonomy code 208800000X).
Where does Dr. Gregory A. Marshall practice?
Dr. Marshall practices at 1601 Ygnacio Valley Rd, Walnut Creek, CA 94598. Dr. Marshall's primary practice is John Muir Medical Center, Walnut Creek in Walnut Creek, California, part of John Muir Health. Dmand AI also links Dr. Marshall to 1 hospital.
What is Dr. Gregory A. Marshall's office phone number?
The practice phone on file for Dr. Marshall is (925) 939-3000.
What is Dr. Gregory A. Marshall's medical license number?
Dr. Marshall holds California license G65068.
Which hospitals is Dr. Gregory A. Marshall affiliated with?
Dr. Marshall practices at John Muir Medical Center, Walnut Creek in Walnut Creek, California. Dr. Marshall is also affiliated with Walnut Creek Medical Center. Dmand AI links Dr. Marshall to 1 more hospital.
What medical group is Dr. Gregory A. Marshall part of?
Dr. Marshall is linked to The Permanente Medical Group, Inc.
Is Dr. Gregory A. Marshall board certified?
Yes. Dr. Marshall is board certified in urology by the American Board of Urology.
Where did Dr. Gregory A. Marshall go to medical school?
Dr. Marshall graduated from Keck School of Medicine of USC in 1987.
What drugs does Dr. Gregory A. Marshall prescribe most?
In 2020 Medicare Part D data, Dr. Marshall's most prescribed drugs by claims were Tamsulosin HCl, Finasteride and Trospium Chloride.
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Has Dr. Gregory A. Marshall received payments from drug or device companies?
CMS Open Payments shows $596 in general payments to Dr. Marshall from 3 companies from 2018 to 2025. The largest total came from Intuitive Surgical, Inc.
How long has Dr. Gregory A. Marshall been practicing?
Dr. Marshall graduated from medical school in 1987, 39 years ago.
Does Dr. Gregory A. Marshall do research?
Dmand AI links 3 publications to Dr. Marshall.
Who does Dr. Gregory A. Marshall publish with?
Dr. Marshall's most frequent co-authors are Peter R. Carroll, MD (1 shared paper) and Gary S. Nicolaisen, MD (1 shared paper).
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