Man-Siak Mak, MD
Gastroenterology Physician · Merced, CA
Man-Siak Mak, MD is a gastroenterology physician with a practice address in Merced, California, and NPI 1609875004, issued on Jul 18, 2005. Check the license (California A26785, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Man-Siak Mak
- Credential
- MD
- Primary taxonomy
- Gastroenterology Physician 207RG0100X
- License number
- A26785 CA
Self-reported in NPPES; status is on the state search - Practice location
- 3349 G Street Ste. F, Merced, CA 95340
- Phone
- (209) 349-8459
- Enumerated
- Jul 18, 2005
- Record last updated
- Apr 17, 2019 (not updated in 7 years: call before relying on the address or phone)
- Fax
- (209) 580-4138
- Medicaid ID
- 00A267850 CA
- Medicare enrollment
- Enrolled (PECOS I20081229000299); accepts Medicare assignment
- Entity
- Type 1 · individual
8 nearest gastroenterology physician records → All 2,140 in California → Look up another NPI →
Verify Man-Siak Mak in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license A26785Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
73% fewer Medicare Part D claims than the average gastroenterology physician in 2024
219 Medicare Part D claims for 102 beneficiaries, against an average of 811 among the 16,445 providers of this specialty who prescribed in Part D. Brand-name drugs were 16% of claims.
Most prescribed
- Gavilyte-G45 claims
- Omeprazole32 claims
- Cholestyramine20 claims
- Peg-3350 And Electrolytes15 claims
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.
Bills Medicare through one group practice
- Timothy S Johnston MD PCMerced, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Man-Siak Mak among 2,140 gastroenterology physician records in California
Man-Siak Mak, MD is one of 2,140 gastroenterology physician records with a practice address in California. 83% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2005, is newer than 0% of them.
- NPI issued2005 · 0% of these records are older, 93% newer
- In a Medicare fileYes · 83% of these records are
- In the CMS Doctors and Clinicians fileYes · 72% of these records are
- Graduated1968 · median 2002 among the 1,538 with a school on file
- Record last updated2019 · 60% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207RG0100X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Gastroenterology Physician providers in California
There are 2,140 gastroenterology physician records in California.
All 2,140 in California → Every provider in Merced → Gastroenterology Physician nationwide →
The 8 gastroenterology physician records with the nearest ZIP codes
- Lillian Choi, MDMerced, CA 953401790769818
- Ripudaman Beniwal, MDManteca, CA 953361528039799
- Howard Marks, M.D.Manteca, CA 953361962479352
- Bhupinder Romana, MDManteca, CA 953361710319447
- Ismail Wadiwala, MDManteca, CA 953361275502171
- Madhu Kris, M.D.Merced, CA 953481427112366
- Sivakumar Munnangi, M.D.Merced, CA 953481447432463
- Tanya Dam, DOModesto, CA 953501104105030
Common questions
What is Man-Siak Mak, MD's NPI number?
Man-Siak Mak, MD's National Provider Identifier (NPI) is 1609875004, issued on Jul 18, 2005. An NPI identifies a provider in billing; it is not a license.
Where is Man-Siak Mak, MD located?
The NPPES record lists a practice address at 3349 G Street Ste. F, Merced, CA, 95340. Phone: (209) 349-8459. Providers update this record themselves, so call before visiting.
How can I verify Man-Siak Mak, MD's license?
NPPES lists California license number A26785, 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 Man-Siak Mak, MD prescribe under Medicare Part D?
In 2024, Man-Siak Mak, MD had 219 Medicare Part D claims for 102 beneficiaries; the average among gastroenterology physician prescribers was 811. 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.