HL7 IS Coded value for user-defined tables
HL7 datatype components IS 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
IS is a coded value from a user-defined table. The values may be local, but they still need to be governed. A free-text value in an IS field is how local codes become impossible to map later.
In this guide, IS appears in CNN, DLD, DLN, DTN, EI, FC and related fields. 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
IS 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 common trap is treating IS as friendly display text. It is a code. The receiving system usually keys off the value and table, so keep the local description, screen label, and mapped code separate in your interface design.
In HL7 Soup Web, click a field that uses IS 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.