Internal Medicine Physicians
David E. Oakley, M.D.
Charles R. Klettner, M.D.
Charles R. Klettner, M.D.
Dr. Oakley graduated from Michigan State University College of Human Medicine. He has practiced at Grand Traverse Internal and Family Medicine since 1995.
Charles R. Klettner, M.D.
Charles R. Klettner, M.D.
Charles R. Klettner, M.D.
Dr. Klettner graduated from Wayne State University School of Medicine. He has practiced at Grand Traverse Internal and Family Medicine since 1997.
Marci R. Bultemeier, D.O.
Charles R. Klettner, M.D.
Marci R. Bultemeier, D.O.
Dr. Bultemeier is a graduate of the University of Health Sciences, College of Osteopathic Medicine, Kansas City. She has practiced at Grand Traverse Internal and Family Medicine since 2001.
Family Practice Physicians
Elizabeth L. Hughes, D.O.
Elizabeth L. Hughes, D.O.
Elizabeth L. Hughes, D.O.
Dr. Hughes graduated from Michigan State University College of Osteopathic Medicine in 2001. She has practiced at Grand Traverse Internal and Family Medicine since 2017.
Jason S. Schreiber, D.O.
Elizabeth L. Hughes, D.O.
Elizabeth L. Hughes, D.O.
Dr. Schreiber graduated from Edward Via College of Osteopathic Medicine in Spartanburg, South Carolina in 2019. He has practiced at Grand Traverse Internal and Family Medicine since July 2023.
Janine M. Kohler, D.O.
Elizabeth L. Hughes, D.O.
Janine M. Kohler, D.O.
Dr. Kohler graduated from Michigan State University College of Osteopathic Medicine in 1996. She has practiced at Grand Traverse Internal and Family Medicine since June 2024.
Endocrinology Team
Jill E. Vollbrecht, M.D.
Jessica A. Mastbergen, DNP
Jessica A. Mastbergen, DNP
Dr. Vollbrecht graduated from Medical College of Wisconsin in 2001. She completed her Endocrinology fellowship in 2007 and has been practicing in the Traverse City area since then. She is accepting new patients aged 18 and up.
Jessica A. Mastbergen, DNP
Jessica A. Mastbergen, DNP
Jessica A. Mastbergen, DNP
Jessica graduated from Grand Valley State University with a Doctorate in Nursing Practice in 2018, and is certified through the American Association of Nurse Practitioners. She provides Endocrinology care under the supervision of Dr. Jill Vollbrecht.
Practice Manager
Tammy Hollenbeck
Tammy’s role is to ensure that all business functions of the business are operating smoothly. She works closely with the physicians and staff to keep them informed, equipped and supported to provide exceptional care to our patients. Her goal is to help people and provide outstanding customer service. She maintains an open-door policy to everyone including patients and families. Tammy joined Grand Traverse Internal and Family Medicine in 2016.