Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of August 10, 2026.
NPIDirectory

Mark C Johnson, MD

Individual provider Internal Medicine Physician · NPI 1013923127

Mark C Johnson, MD is an Endocrinology in Mason City, Iowa. Graduated from University of Iowa, Rj & L Carver College of Medicine in 1977, 49 years ago. Practices with North Iowa Mercy Clinics, a 300-clinician group and accepts Medicare assignment. Licensed in Iowa.

Years since qualifying
49
Trained at
University of Iowa, Rj & L Carver College of Medicine
Licensed in
IA
In the registry since
2006
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.

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Practice location Address checks out

910 N Eisenhower Ave
Mason City, IA 50401-2800
Phone: (641) 428-7799
Fax: (641) 428-5274
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Internal Medicine Physician (primary) Taxonomy 207R00000X · Licence 21527 (IA)

Record details

NPI number1013923127
Entity typeIndividual (Type 1)
GenderMale
Credentials MD
Sole proprietorNo
NPI enumeratedJuly 31, 2006
Last updated in NPPESJuly 8, 2025
Certification dateJuly 8, 2025
Mailing address621 S Illinois Ave, Suite 103, Mason City, IA 50401-5489

Medicare enrollment

From the CMS Doctors & Clinicians file — this clinician is enrolled in Medicare.

Medicare specialtyENDOCRINOLOGY
Also practisesINTERNAL MEDICINE
Medical schoolUNIVERSITY OF IOWA, RJ & L CARVER COLLEGE OF MEDICINE
Graduated 1977 (49 years in practice)
Group practice North Iowa Mercy Clinics — 300 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount

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