RXR-2 in HL7 v2: A Field Guide to Administration Site
RXR-2 is technically optional in the standard, but for anyone tracking injection sites — think rotating vaccine locations across a series of doses — it is effectively required, and its absence is one of the more common data-quality complaints from downstream MAR systems.
RXR-2 is a coded element (CE/CWE) identifying the anatomical body site where a dose was administered, such as an arm, thigh, or buttock, often with laterality (left/right) included in the display text or a separate component. It is most relevant for injectable and topical products and is frequently left blank for oral or systemic routes where a specific site doesn't apply.
What this field contains
Example
RXR-2 carries LD^Left Deltoid^HL70163, pinpointing the exact injection site for the paired intramuscular dose.
Where this trips people up
Because RXR-2 is optional, some sending systems never populate it even for injectable products, and some receiving systems assume it will always be present for anything coded IM or SC in RXR-1. Test suites that only generate site values alongside injected routes never exercise the case where a real feed legitimately omits it, or the opposite case — a topical or oral route that unexpectedly includes a site value the parser wasn't built to ignore. Both directions cause silent data loss or unnecessary validation failures in production.