MARK DREYER, M.D. appears in the CMS NPPES registry as a Gastroenterology Physician provider holding M.D. credentials at 1111 DELAFIELD ST, WAUKESHA, WI, 53188, with a listed phone of (262) 544-8622. NPI 1396714861 was issued on 03/16/2006. Because NPPES data is self-reported by the provider and refreshed monthly, the address, phone, and specialty reflect what DREYER 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 prescribing data is not currently published for this NPI, which typically means the provider either wrote fewer than 11 Part D claims in the most recent reporting year, does not participate in Medicare, or practices in a specialty that rarely prescribes outpatient drugs. Absence of prescribing data is not a quality signal — many Gastroenterology Physician providers operate outside Part D entirely.

Gastroenterology Physician is a mid-sized specialty nationwide, with 16,567 enrolled providers across 54 states and an average of 833 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.