Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum Sole proprietor

Dr. Calvin L Day Jr., M.D.

MOHS-Micrographic Surgery Physician in San Antonio, TX · enumerated 2007 · practices at Skin Cancer Dermatology, Pllc.

Data current as of Jul 13, 2026 · sourced from CMS NPPES

National Provider Identifier

1831379692

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Registry record

Entity type Individual (Type 1)

Name Dr. Calvin L Day Jr.

Credential M.D.

Sex Male

Practice address San Antonio, TX, 78209

Phone (210) 601-6502

Fax (830) 885-6691

Enumeration date Nov 9, 2007

Last updated in NPPES Aug 25, 2023

Street address withheld: NPPES sole-proprietor addresses can be home addresses. See our data policy.

Taxonomy & licenses

207NS0135X Procedural Dermatology Physician Allopathic & Osteopathic Physicians · License G1883 (TX) Secondary

207ND0101X MOHS-Micrographic Surgery Physician Allopathic & Osteopathic Physicians · License G1883 (TX) Primary

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
45D2258975	Other	TX	CLIA

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.

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Frequently asked questions

What specialty is Calvin Day?

Calvin Day is registered in NPPES with the primary taxonomy of MOHS-Micrographic Surgery Physician. The taxonomy code describes the provider's classification and area of specialization for claims and credentialing.

Is this the official NPI registry?

No. NPI Portal is a private site built on public CMS NPPES data. The official registry is npiregistry.cms.hhs.gov, operated by CMS.

Other providers at this practice address

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Skin Cancer Dermatology, Pllc MOHS-Micrographic Surgery Physician · San Antonio, TX NPI 1649800848

Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2023-08-25.