Coding Standards
Logical Observation Identifiers Names and Codes(LOINC)
Regenstrief-maintained code system that names laboratory tests, clinical observations, and document types.
Definition
LOINC (Logical Observation Identifiers Names and Codes) is a standard for naming clinical observations and laboratory results, maintained by the Regenstrief Institute. Where ICD-10 names diseases, LOINC names what was measured: each LOINC code identifies a single test, panel, or observation by six axes (component, property, time aspect, system, scale type, method). For example, 718-7 is "Hemoglobin [Mass/volume] in Blood".
LOINC is the standard for lab and clinical observation reporting in HL7 v2 and FHIR (the Observation.code element typically carries a LOINC code). It is also widely used for document type identification (LOINC document ontology), survey instruments, and clinical questionnaires.
LOINC and ICD-10 are complementary, not interchangeable. A LOINC tells you "this is a glucose measurement"; ICD-10 tells you "diabetes mellitus". A claim or chart often cites both: an ICD-10 diagnosis and one or more LOINC observation codes that supported it.
When to use
- •Building lab interfaces, FHIR Observation resources, or HL7 v2 ORU messages.
- •Mapping legacy lab catalogs to a standard ontology.
- •Quality measurement workflows (HEDIS, CMS eCQMs) that reference LOINC observation codes.
Try it in AutoICD API
Code a lab observation to LOINC
curl -X POST https://autoicdapi.com/v1/loinc/code \
-H "Authorization: Bearer $AUTOICD_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"text": "fasting glucose 126 mg/dL"
}'Language: bash. View full API docs · Get an API key.