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DR. MAN-SIAK MAK MD
NPI 1609875004
Internal Medicine - Gastroenterology in Merced, CA

Active since July 18, 2005PECOS EnrolledAccepts Medicare Assignment
3349 G STREET STE. F, MERCED, CA 95340(209) 349-8459(209) 580-4138 Get Directions Write a Review

NPPES record last updated: April 17, 2019. Verified against the NPPES registry weekly; last sync: November 01, 2026.

About Dr. Man-siak Mak Md NPPES

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

DR. MAN-SIAK MAK MD (NPI 1609875004) is an individual gastroenterology provider in Merced, California, licensed in California (A26785) and active in the NPI registry since July 2005. He is enrolled in Medicare PECOS and is a graduate of Other (1968).

NPPES Registry Identity

NPI1609875004
Entity TypeIndividualMale
Primary Taxonomy207RG0100X
Provider Legal NameDR. MAN-SIAK MAKCredential: MD
Location Address3349 G STREET STE. FMerced, CA 95340
Mailing Address3349 G Street Ste. FMerced, CA 95340 · (209) 349-8459 · Fax (209) 580-4138
Phone(209) 349-8459
Fax(209) 580-4138
Sole ProprietorYes
Medical School CMSOtherGraduated 1968
Enumeration DateJuly 18, 2005
Last NPPES UpdateApril 17, 2019
✔ NPI 1609875004 is a valid, active identifier and passes the ISO check-digit test.

Specialties & Licenses

★ Primary SpecialtyInternal Medicine · GastroenterologyAllopathic & Osteopathic Physicians
Taxonomy Code207RG0100X
License✔ Licensed in CA · A26785
Definition
An internist who specializes in diagnosis and treatment of diseases of the digestive organs including the stomach, bowels, liver and gallbladder. This specialist treats conditions such as abdominal pain, ulcers, diarrhea, cancer and jaundice and performs complex diagnostic and therapeutic procedures using endoscopes to visualize internal organs.
3349 G STREET STE. F, Merced, CA 95340
Open in Google Maps ↗

Other Identifiers 1

Medicaid00A267850CA

Medicare Participation & PECOS CMS

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

Medicare Enrollment Status

✔

Enrolled in Medicare and accepts Medicare assignment

Dr. Man-siak Mak Md is registered in PECOS and agrees to accept the Medicare-approved amount as full payment. Medicare patients are not billed beyond the standard deductible and coinsurance.

PECOS PAC ID4183786122
PECOS Enrollment IDI20081229000299
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 Reassignment

Medicare enrollment records show Man-siak Mak reassigns Medicare billing to 1 organization. The organization bills Medicare for the services this provider delivers there.

Timothy S. Johnston, M.D. PC
Same address
Bone Densitometry
3349 G ST STE B
Merced, CA 95340
  • Reassigned Medicare billing, California enrollment
  • Medicare enrollment name: Timothy S Johnston MD PC
  • 17 clinicians in this Medicare group
NPI 1033614193 (209) 233-3715

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

Areas of Expertise CMS Part B claims 8

Services this provider delivered to Medicare fee-for-service patients, from the CMS Medicare utilization data. Higher counts generally reflect more experience with a service; care delivered outside Medicare is not included.

Established patient office or other outpatient visit with low level od decision making, if using time, 20 minutes or more 99213
This is a routine visit for patients who have already been seen by the healthcare provider. During this approximately 20-29 minute appointment, your health status will be evaluated and any necessary treatments or tests will be discussed. It's a chance to address any health concerns you may have.
189 services105 patients
Established patient office or other outpatient visit with moderate level of decision making, if using time, 30 minutes or more 99214
This is a routine check-up for patients who have previously visited our clinic. It involves a comprehensive review of your health and any ongoing treatments. The consultation lasts between 30-39 minutes, allowing enough time to discuss any concerns.
123 services77 patients
New patient office or other outpatient visit with moderate level of medical decision making, if using time, 45 minutes or more 99204
This is a first-time office or outpatient visit lasting between 45-59 minutes. The healthcare provider evaluates your health, discusses your medical history, and may suggest further tests or treatments. It's an opportunity to ask questions and understand your health better.
79 services79 patients
Biopsy of esophagus, stomach, and/or upper small bowel using a flexible endoscope 43239
This procedure involves using a thin, flexible tube with a light and camera, known as an endoscope, to examine the esophagus, stomach, and upper part of the small intestine. Small tissue samples are taken for further examination to help diagnose various conditions.
28 services27 patients
Removal of polyps or growths of large bowel using an endoscope with mechanical snare 45385
This procedure involves using a thin, flexible tube called an endoscope to examine the large bowel. If any abnormal growths or polyps are found, a tool called a mechanical snare is used to remove them. This is a common method to prevent potential health issues.
28 services27 patients
Biopsy of large bowel using a flexible endoscope 45380
A biopsy of the large bowel using a flexible endoscope is a procedure where a thin, flexible tube with a camera is inserted through the rectum to examine the bowel. If abnormal tissue is found, a small sample is taken for further examination. This helps in diagnosing conditions like inflammation, polyps, or cancer.
20 services19 patients

Physician Visit Costs CMS claims · ZIP area

Typical Medicare office-visit costs in the 95340 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
$133.94 typical visit price
range $58.87 – $176.60
Typical copayment $33.48 (range $14.71 – $44.15)
Most-billed visit code 99204
Established Patient
$103.36 typical visit price
range $19.28 – $144.60
Typical copayment $25.84 (range $4.82 – $36.15)
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.

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 Man-siak Mak's NPI number?

The NPI number for Man-siak Mak is 1609875004. It was assigned to this individual provider in the NPPES registry on July 18, 2005.

Where is Man-siak Mak located?

Man-siak Mak practices at 3349 G Street Ste. F, Merced, CA 95340. The listed phone number is (209) 349-8459.

What is Man-siak Mak's specialty?

The primary specialty registered for this NPI is Internal Medicine, specializing in Gastroenterology, with taxonomy code 207RG0100X.

Is Man-siak Mak enrolled in Medicare?

Yes. Man-siak Mak is registered in the Medicare PECOS system and accepts Medicare assignment, which means accepting the Medicare-approved amount as payment in full for covered services.

Which organization bills Medicare for Man-siak Mak's services?

According to the CMS Revalidation Reassignment List (October 2026 release), Man-siak Mak reassigns Medicare benefits to Timothy S. Johnston, M.D. PC (Merced, CA). The 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 Man-siak Mak'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 Man-siak Mak was last updated on April 17, 2019. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 7 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.