Recently Updated NPI Information — some details in this NPI profile have been updated in the NPI registry within the last 60 days.

DR. WILLIAM CHARLES O'CALLAHAN JR. MD
NPI 1114964186
Emergency Medicine in Holden, MA

Q: What is William O'callahan's NPI number?

The NPI number for William O'callahan is 1114964186. It was assigned to this individual provider in the NPPES registry on May 31, 2006.

Q: What is William O'callahan's specialty?

The primary specialty registered for this NPI is Emergency Medicine with taxonomy code 207P00000X.

Active since May 31, 2006PECOS EnrolledAccepts Medicare Assignment

5 SHREWSBURY ST STE D, HOLDEN, MA 01520(508) 829-3800(508) 829-3802 Get Directions Write a Review

NPPES record last updated: October 4, 2026. Verified against the NPPES registry weekly; last sync: October 18, 2026.

Record update history: Oct 4, 2026, Mar 16, 2023 (2 updates tracked since 2023).

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About Dr. William Charles O'callahan Jr. Md NPPES

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

DR. WILLIAM CHARLES O'CALLAHAN JR. MD (NPI 1114964186) is an individual emergency medicine provider in Holden, Massachusetts, licensed in Massachusetts (79001) and active in the NPI registry since May 2006. He is enrolled in Medicare PECOS, is affiliated with Umass Memorial Medical Center/university Campus, and maintains 2 additional practice locations.

NPPES Registry Identity

NPI1114964186

Entity TypeIndividualMale

Primary Taxonomy207P00000X

Provider Legal NameDR. WILLIAM CHARLES O'CALLAHAN JR.Credential: MD

Location Address5 SHREWSBURY ST STE DHolden, MA 01520-1960

Mailing Address5 Shrewsbury St Ste DHolden, MA 01520-1960 · (508) 829-3810 · Fax (508) 829-3815

Phone(508) 829-3800

Fax(508) 829-3802

Sole ProprietorNo

Medical School CMSUniversity Of Massachusetts Medical SchoolGraduated 1990

Enumeration DateMay 31, 2006

Last NPPES UpdateOctober 4, 20262 updates tracked since enumeration

NPPES CertifiedOctober 4, 2026

✔ NPI 1114964186 is a valid, active identifier and passes the ISO check-digit test.

Specialties & Licenses

★ Primary SpecialtyEmergency MedicineAllopathic & Osteopathic Physicians

Taxonomy Code207P00000X

License✔ Licensed in MA · 79001

Definition

An emergency physician focuses on the immediate decision making and action necessary to prevent death or any further disability both in the pre-hospital setting by directing emergency medical technicians and in the emergency department. The emergency physician provides immediate recognition, evaluation, care, stabilization and disposition of a generally diversified population of adult and pediatric patients in response to acute illness and injury.

5 SHREWSBURY ST STE D, Holden, MA 01520

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Secondary Practice Locations 2

Location 1688 Bliss RdLongmeadow, MA 01106-1534 · Phone (413) 567-0011 · Fax (413) 567-0013

Location 22040 Boston Rd Ste 5Wilbraham, MA 01095-1380 · Phone (413) 599-3800 · Fax (413) 279-1900

Other Identifiers 2

Medicaid110054527AMA

Medicaid008143267CT

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. William Charles O'callahan Jr. 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 ID3072692805

PECOS Enrollment IDI20080506000317

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 William O'callahan reassigns Medicare billing to 1 organization. The organization bills Medicare for the services this provider delivers there.

Urgent Care Specialists PC

Same address

Urgent Care

5 SHREWSBURY ST STE D
Holden, MA 01520

Reassigned Medicare billing, Massachusetts enrollment
2 clinicians in this Medicare group

NPI 1720497985 (508) 829-3800

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 14

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.

188 services179 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.

179 services173 patients

X-ray of chest, 2 views 71046

A chest X-ray, 2 views, is a quick, painless test that creates pictures of the structures inside your chest, such as your heart, lungs, and blood vessels. Two different angles are used to get a comprehensive view. This helps in diagnosing conditions like pneumonia, heart problems, or lung cancer.

121 services112 patients

New patient office or other outpatient visit with low level of medical decision making, if using time, 30 minutes or more 99203

This service involves an initial office or outpatient visit for a new patient. The healthcare professional will spend 30-44 minutes understanding your health history, current issues, and discussing possible treatment plans. It's a comprehensive evaluation to start your healthcare journey.

88 services88 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.

86 services86 patients

Detection test by multiplex amplified probe technique for severe acute respiratory syndrome coronavirus 2 (sars-cov-2) (covid-19) and influenza virus types a and b 87636

This test detects the presence of SARS-CoV-2 (COVID-19) and Influenza types A and B in your body. It uses a method called the multiplex amplified probe technique to amplify and identify specific virus genes. It helps in early diagnosis and appropriate treatment.

66 services66 patients

Detection test by nucleic acid for multiple types of respiratory virus, multiple types or subtypes, 3-5 targets 87631

This test identifies different respiratory viruses by examining their nucleic acid, the building blocks of their genetic material. It can detect multiple types or subtypes, specifically 3-5 targets. This helps in diagnosing your respiratory illness accurately.

62 services62 patients

Amplifed dna or rna probe detection of severe acute respiratory syndrome coronavirus 2 (covid-19) antigen 87635

This is a lab test that detects the presence of COVID-19 in your body. It uses a technique to amplify the virus's genetic material, either DNA or RNA, making it easier to identify. A positive result indicates an active infection.

51 services51 patients

Automated urinalysis test 81003

An automated urinalysis test is a routine examination that checks your urine for various substances. It can help identify potential health issues such as kidney problems or diabetes. The test uses a machine to analyze a small urine sample, providing quick and accurate results.

47 services47 patients

Detection test by nucleic acid for strep (streptococcus, group a), amplified probe technique 87651

This test detects Group A Streptococcus bacteria in your body. It uses an amplified probe technique, which amplifies the bacteria's nucleic acid, making it easier to identify. This test helps diagnose conditions like strep throat or scarlet fever.

46 services46 patients

Analysis for antibody borrelia burgdorferi (lyme disease bacteria) 86618

This test checks for antibodies in your blood that your body may produce in response to Borrelia burgdorferi, the bacteria causing Lyme disease. It helps confirm if you've been infected by a tick carrying this bacteria.

17 services12 patients

X-ray of foot, minimum of 3 views 73630

An X-ray of the foot, minimum of 3 views, is a non-invasive imaging test. It uses a small amount of radiation to produce images of the bones and tissues in your foot. This helps to identify fractures, infections, or other abnormalities. Multiple views ensure a comprehensive examination.

14 services13 patients

Routine electrocardiogram (ecg) using at least 12 leads with interpretation and report 93000

An electrocardiogram (ECG) is a non-invasive test that records your heart's electrical activity. Using 12 leads attached to your body, it captures data to help identify heart conditions. A doctor interprets the results and provides a report.

12 services12 patients

Detection test by immunoassay with direct visual observation for respiratory syncytial virus 87807

This is a test to identify the respiratory syncytial virus, a common cause of lung and respiratory tract infections. It uses immunoassay, a method that detects the virus through a reaction between the virus and specific antibodies. The result is visually observed.

11 services11 patients

Hospital Affiliations CMS Care Compare

Hospitals where this provider delivers care, identified from recent Medicare claims and place-of-service records.

Umass Memorial Medical Center/University Campus

Acute Care Hospitals · Worcester, MA

4/5 CMS rating

OwnershipVoluntary non-profit - Private

CMS Certification Number220163

Location55 Lake Avenue NorthWorcester, MA 01655 · Worcester County

Emergency services Birthing friendly

Physician Visit Costs CMS claims · ZIP area

Typical Medicare office-visit costs in the 01520 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

$90.70 typical visit price

range $58.86 – $177.36

Typical copayment $22.67 (range $14.71 – $44.34)

Most-billed visit code 99203

Established Patient

$103.48 typical visit price

range $19.11 – $144.84

Typical copayment $25.87 (range $4.77 – $36.21)

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.

Other Providers at the Same Location NPPES 10

Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.

MRS. KAREN-WHITLEY BISHOP PA

Physician Assistant