Developer Reference for LOINC in FHIR


LOINC's FHIR terminology server utilizes HAPI FHIR, the open-source implementation of FHIR in Java. LOINC's instance is built using software provided by Smile CDR.

All requests to LOINC's FHIR terminology server require a LOINC username and password.


More Info

We also suggest you review HL7's documentation regarding LOINC terminology, 4.2.3 Using LOINC with FHIR. Furthermore, the LOINC Users' Guide can help you understand all the intricacies of the LOINC code system.

You may also post questions and feedback in our User Forum for this server.

Canonical URI for LOINC in FHIR

Canonical definition for LOINC as a CodeSystem in FHIR

REST endpoint base

The following endpoints omit this base for brevity.

CodeSystem endpoint

Returns all information about LOINC as a CodeSystem.


Identifier lookup operation

May be used on a LOINC term, Part, Answer List, or Answer.

/CodeSystem/$lookup?system={LOINC identifier}

Lookup specific property

Indicate particular property(ies) for an identifier

/CodeSystem/$lookup?system={LOINC identifier}&&property={Property}[&&property={Property}]

ValueSet endpoint

Returns entire ValueSet resource including all available value sets, definition criteria, etc.


Specific ValueSet

Returns the ValueSet resource for the identified Answer List, LOINC Group, or general collection of LOINC terms.

/ValueSet/?url={LOINC identifier}
/ValueSet/{LOINC identifier}

Expand ValueSet operation

Returns the expansion for given ValueSet.

/ValueSet/$expand?url={LOINC ValueSet identifier}

Validate term in given ValueSet

Returns boolean true if term exists in given ValueSet.

/ValueSet/{LOINC ValueSet}/$validate-code?system={LOINC identifier}

ConceptMap endpoint

Returns all available LOINC concept mappings, metadata, mappings, and canonical URIs.


Specific ConceptMap

Returns the ConceptMap resource for identified set.

/ConceptMap/?url={Canonical LOINC ConceptMap URI}

Translate operation

Return available mapping(s) for identified LOINC source term.

/ConceptMap/$translate?system={LOINC identifier}

Questionnaire endpoint

Returns all forms available within LOINC.


Specific Questionnaire

Returns the Questionnaire resource for the identified term.

/Questionnaire/?url={LOINC identifier}