WILLIAM CHAO, MD appears in the CMS NPPES registry as a Emergency Medicine Physician provider holding MD credentials at 1011 BALDWIN PARK BLVD, BALDWIN PARK, CA, 91706, with a listed phone of (626) 851-1011. NPI 1841348661 was issued on 01/08/2007. Because NPPES data is self-reported by the provider and refreshed monthly, the address, phone, and specialty reflect what CHAO 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 397 prescription claims written by this provider, covering 272 Medicare beneficiaries and totaling roughly $11K in drug spend, split 6% brand-name and 94% generic by claim count, with an opioid prescribing rate of 11.3%. 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.

Emergency Medicine Physician is a high-volume specialty nationwide, with 64,398 enrolled providers across 56 states and an average of 352 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.