Quick answers
- Where does William Callahan see patients?
- Medicare's clinician data lists 1 practice location in Marshfield, MA. Call before your visit to confirm the address.
- What is William Callahan's specialty?
- Medicare lists Optometry as the primary specialty.
- Does William Callahan accept Medicare assignment?
- Yes. Medicare's clinician data says William Callahan accepts Medicare assignment (the Medicare-approved amount as full payment for covered services), as of 2026-10-02. Ask the office to confirm before your visit.
- What is the phone number for William Callahan?
- (781) 837-9956, as listed in official Medicare / NPI Registry data.
- What is William Callahan's NPI number?
- 1568536357. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Practice locations
Addresses where William Callahan is enrolled with Medicare (CMS data updated 2026-10-02).
- 462 Plain StMarshfield, MA 02050 (781) 837‑9956
Specialties
- Optometryprimary
Other optometrists in Massachusetts
Clinicians with the same Medicare primary specialty in Massachusetts — not a recommendation.
Clinician information
| Medical school | New England College Of Optometry |
|---|---|
| Graduation year | 1983 |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1568536357 |
| Corrections | Report an error or suggest an update → |
Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.
Sources
- National Downloadable File (Doctors and Clinicians) — CMS, data updated 2026-10-02, retrieved 2026-10-29
- NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
- Medicare Care Compare — official Medicare tool to look up clinicians