HL7 NUL HL7 NUL data type
HL7 datatype components NUL components from HL7 v2.5.1 Hide components
These are the generated components for the version selected at the top of the page. The article stays practical, and this panel follows the chosen HL7 version.
Components
NUL is the HL7 null datatype. It is not a place to put a value; it exists for fields that are effectively not populated by design or retained only for compatibility.
In this guide, NUL appears in MSA.5. That used-by list is a good reality check: the datatype is only half the story, and the field that uses it tells you the workflow.
The component panel above is expanded by default because most datatype pages are used as quick lookup pages. Start there for the exact HL7 v2.5.1 shape, then use the notes below for the practical gotchas.
The Value
NUL is primitive in this v2.5.1 reference data, so there are no caret-separated components to expand. The whole field value is the datatype value. That makes it quick to read, but it also means validation has to happen at the field level: the datatype will not give you extra components to explain what the value means.
Practical Notes
The safest habit is to populate only the components the receiving profile actually uses, and to keep each meaning in its own component. Empty components are better than a compact display string that a receiver has to reverse-engineer.
In HL7 Soup Web, click a field that uses NUL to see the field meaning beside the raw value. For primitive datatypes, that quick field-level check is usually more useful than looking for components that do not exist.
Official and Reference Notes
For formal reference, compare the generated HL7 v2.5.1 panel above with the HL7 v2.5.1 datatype list and the HL7 Terminology data type code system. Local implementation guides can narrow allowed values, tables, and component usage.