Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum
William Thomas Callahan, MD
Specialist in Gainesville, GA · enumerated 2005.
Data current as of Jul 13, 2026 · sourced from CMS NPPES
National Provider Identifier
1356344535
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Registry record
Entity type Individual (Type 1)
Name William Thomas Callahan
Credential MD
Sex Male
Practice address 663 Lanier Park Dr, Gainesville, GA, 30501
Phone (770) 536-8109
Fax (770) 536-3203
Enumeration date May 23, 2005
Last updated in NPPES May 29, 2008
Taxonomy & licenses
MD · Doctor of Medicine: A physician who completed medical school (allopathic medicine), residency training, and state licensure.
About the MD credential
Other identifiers
| Identifier | Type | State | Issuer |
|---|---|---|---|
| 00162126A | Medicaid | GA | - |
What is an NPI number?
A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes, even if the provider moves or changes specialty.
Frequently asked questions
Is NPI 1356344535 active?
Yes, as of the latest NPPES snapshot, NPI 1356344535 is active (record last updated 2008-05-29).
How do I verify William Callahan's NPI record?
Cross-check NPI 1356344535 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.
Other providers at this practice address
Browse all → Lalitha Bandi Nephrology Physician · Gainesville, GA NPI 1942203138 Khaled Nass Nephrology Physician · Gainesville, GA NPI 1861495830 Sohail Saleem Nephrology Physician · Gainesville, GA NPI 1932102993 Adebowale Oguntola Nephrology Physician · Gainesville, GA NPI 1336121946 Vesna Rizvanovic Medical Physician Assistant · Gainesville, GA NPI 1811965312 Rahim Kassamali Nephrology Physician · Gainesville, GA NPI 1932162641 Sohail Ejaz Nephrology Physician · Gainesville, GA NPI 1942263678 Ernest Han Nephrology Physician · Gainesville, GA NPI 1942357744
Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2008-05-29.