An email subject line has to be HIPAA compliant when it contains protected health information because the subject line is part of the message content that can be created, received, maintained, or transmitted by a HIPAA Covered Entity or Business Associate and is subject to the HIPAA Privacy Rule and, when handled electronically, the HIPAA Security Rule.
A subject line can create an impermissible disclosure if it includes patient identifiers or clinical details that are not permitted for the recipient, are not limited to the HIPAA Minimum Necessary Rule for the purpose, or are exposed to unintended parties through inbox previews, shared devices, forwarding, or misaddressing. Even when an organization uses an approved email service and applies transmission protections, a subject line can still be displayed in places that are outside the sender’s control, including notification banners, lock screens, mail client previews, and some mail routing or logging contexts.
Operational controls for subject lines start with content restrictions. Organizations typically prohibit including diagnosis terms, procedure names, test results, or other sensitive descriptors in the subject line when a patient name, medical record number, or other identifier is present, and they restrict use of identifiers in subject lines unless there is a defined work need. Internal workflows can use neutral subjects paired with message body content that is limited to the minimum necessary and protected through approved safeguards.
Patient communications require additional control. When emailing an individual, a covered entity must follow the individual’s communications requests when reasonable and apply reasonable safeguards for the content transmitted. If an individual requests email communications, the organization should still limit subject lines to administrative language that does not reveal protected health information, and the organization should document any preferences that increase disclosure risk in line with its privacy procedures.
Compliance programs address subject lines through policy, training, and technical enforcement. Policies define permitted subject line formats, external sending rules, and sanctions for noncompliance. Technical controls can include data loss prevention rules, external recipient warnings, and restrictions on auto-forwarding and delegation that increase the risk of unintended access. When a subject line includes protected health information and is sent to an incorrect recipient or exposed through unauthorized access, the organization must evaluate the event under the HIPAA Breach Notification Rule and apply mitigation and corrective action procedures.