WILLIAM CHEN, MD appears in the CMS NPPES registry as a Allergy & Immunology Physician provider holding MD credentials at 2089 VALE RD, SAN PABLO, CA, 94806, with a listed phone of (510) 235-9247. NPI 1851498372 was issued on 09/19/2006. Because NPPES data is self-reported by the provider and refreshed monthly, the address, phone, and specialty reflect what CHEN 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 17,960 prescription claims written by this provider, covering 888 Medicare beneficiaries and totaling roughly $2.6 million in drug spend, split 15% brand-name and 85% generic by claim count, with an opioid prescribing rate of 6.9%. 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. On the CMS Merit-based Incentive Payment System, this provider earned a Final Score of 81.0836/100 for the 2023 performance year (Quality 71.3476, Cost 58.4817), compared with the national average of 83.1.

Allergy & Immunology Physician is a narrow specialty nationwide, with 3,390 enrolled providers across 52 states and an average of 764 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.