The opioid crisis is one of the largest public health problems in the history of the United States. Prescription drug monitoring programs (“PDMPs”)—state databases containing the records of all prescriptions for controlled substances written in the state—have emerged as a means to track opioid prescribing and use. While PDMPs are typically used as a tool for physicians to inform their prescribing practices, many states also permit law enforcement to access PDMPs when investigating controlled substance distribution, often without prior judicial approval. Such law enforcement use of PDMPs raises serious questions of patient privacy. The Fourth Amendment protects individuals from unreasonable searches and seizures where they have a reasonable expectation of privacy and has been interpreted to require law enforcement have probable cause and a search warrant before infringing upon an individual’s reasonable expectation of privacy. Several courts have held that patients have no reasonable expectation of privacy, or a severely diminished expectation of privacy, in their prescription drug records held in PDMPs. As support, courts rely on the third-party doctrine because the information is disclosed to physicians and then held by the state; the highly regulated nature of the prescription drug industry; and the statutory framework of the Controlled Substances Act. Such analysis disregards patients’ expectation of privacy in their personal health information, the confidentiality in the physician-patient relationship, and the resulting patient incentives not to seek care. Therefore, this Article argues that law enforcement must have probable cause and a search warrant to access PDMPs because the exceptions to the Fourth Amendment’s probable cause and warrant requirements do not apply.