WILLIAM GUENTHER, M.D. appears in the CMS NPPES registry as a Hematology & Oncology Physician provider holding M.D. credentials at 3925 N GATEWAY DR, APPLETON, WI, 54913, with a listed phone of (920) 749-1171. NPI 1386789618 was issued on 02/21/2007. Because NPPES data is self-reported by the provider and refreshed monthly, the address, phone, and specialty reflect what GUENTHER most recently submitted to CMS rather than a vetted directory listing, which is why patients should always confirm the practice is still at this location before scheduling.

Medicare Part D records for calendar year 2023 show 21 prescription claims written by this provider, covering 12 Medicare beneficiaries and totaling roughly $22K in drug spend, split 52% brand-name and 48% generic by claim count. These figures capture only Medicare Part D — commercial insurance, Medicaid, and cash-pay prescriptions are not included, and any drug-beneficiary cell under 11 is suppressed by CMS for patient privacy.

Hematology & Oncology Physician is a mid-sized specialty nationwide, with 11,215 enrolled providers across 54 states and an average of 847 Part D claims per prescriber, so the context for interpreting these metrics differs meaningfully from a primary-care baseline. Important: PlainDoctor is a directory of publicly available government data, not medical advice, a malpractice database, or a quality rating. Inclusion here does not imply a recommendation, and absence of complaints or sanctions on this page does not mean none exist — always verify credentials through the NPPES NPI Registry, your state medical board, and the ABMS or AOA before making healthcare decisions.