Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Karl Elliott Terwilliger, MD

Anesthesiology Physician in Waterloo, IA · enumerated 2006.

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

National Provider Identifier

1669426060

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Registry record

Entity type Individual (Type 1)

Name Karl Elliott Terwilliger

Credential MD

Sex Male

Practice address 1825 Logan Ave, Waterloo, IA, 50703

Phone (319) 235-3886

Fax (319) 233-1630

Enumeration date May 20, 2006

Last updated in NPPES Sep 12, 2007

Taxonomy & licenses

207L00000X Anesthesiology Physician Allopathic & Osteopathic Physicians · License 34416 (IA) 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
43625	Other	IA	WELLMARK INS
0250993	Medicaid	IA	-
421417307F6	Other	IA	JOHN DEERE HEALTH INS

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

What is the NPI number for Karl Terwilliger?

The National Provider Identifier (NPI) for Karl Terwilliger is 1669426060, a Type 1 (individual) record in the CMS NPPES registry.

Where does Karl Terwilliger practice?

The practice location on file with NPPES is in Waterloo, IA. Providers can have multiple locations; NPPES lists the primary practice address.

Other providers at this practice address

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2007-09-12.