Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Dr. Tad Mark Johnson, MD

Allergy Physician in Janesville, WI · enumerated 2006.

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

National Provider Identifier

1659339919

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Registry record

Entity type Individual (Type 1)

Name Dr. Tad Mark Johnson

Credential MD

Sex Male

Practice address 3524 E Milwaukee St, Janesville, WI, 53546

Phone (608) 756-7100

Fax (608) 756-4700

Enumeration date May 3, 2006

Last updated in NPPES Sep 6, 2012

Taxonomy & licenses

207KA0200X Allergy Physician Allopathic & Osteopathic Physicians · License 25307 (WI) 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
JOHNSTAD	Other	WI	MERCYCARE INSURANCE
1659339919	Other	WI	BCBSWI
1659339919	Medicaid	WI	-
30661900	Medicaid	WI	-

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.

Read the full guide → Validate an NPI →

Frequently asked questions

Is NPI 1659339919 active?

Yes, as of the latest NPPES snapshot, NPI 1659339919 is active (record last updated 2012-09-06).

How do I verify Tad Johnson's NPI record?

Cross-check NPI 1659339919 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2012-09-06.