LOINC API

Look up LOINC codes for laboratory and clinical observations.

Overview

LOINC (Logical Observation Identifiers Names and Codes) is the universal standard for identifying laboratory and clinical observations. FHIRfly provides fast lookups against the Regenstrief LOINC database.

Endpoints

Method	Path	Description
GET	`/v1/loinc/:code`	Single LOINC lookup
POST	`/v1/loinc/_batch`	Batch LOINC lookup (up to 100)
GET	`/v1/loinc/shapes`	List available response shapes

Single Lookup

Look up Glucose in Blood test

Request

Node.js

import { Fhirfly } from "@fhirfly-io/terminology";

const client = new Fhirfly({ apiKey: "YOUR_API_KEY" });

const result = await client.loinc.lookup("2339-0");
console.log(result.data);

Response

JSON

{
  "data": {
    "class": "CHEM",
    "code": "2339-0",
    "display_name": "Glucose, Blood",
    "fhir_coding": {
      "code": "2339-0",
      "display": "Glucose, Blood",
      "system": "http://loinc.org"
    },
    "long_name": "Glucose [Mass/volume] in Blood",
    "map_to": [],
    "order_obs": "Both",
    "parts": {
      "component": "Glucose",
      "method_typ": null,
      "property": "MCnc",
      "scale_typ": "Qn",
      "system": "Bld",
      "time_aspct": "Pt"
    },
    "shortname": "Glucose Bld-mCnc",
    "status": "ACTIVE",
    "units": {
      "example_ucum_units": "mg/dL",
      "example_units": "mg/dL"
    }
  },
  "meta": {
    "legal": {
      "attribution_required": true,
      "citation": "LOINC from Regenstrief Institute. Accessed 2026-01-14 via FHIRfly.",
      "license": "regenstrief_license",
      "source_name": "LOINC",
      "terms_of_use": "https://loinc.org/license/"
    }
  }
}

LOINC Code Format

LOINC codes follow the format NNNNN-N (e.g., 2339-0):

First part: 1-5 digits
Hyphen
Check digit

LOINC Code Parts

Part	Description
Component	What is measured (e.g., Glucose)
Property	Type of measurement (e.g., MCnc = Mass concentration)
Time	Point in time vs interval
System	Specimen type (e.g., Bld = Blood)
Scale	Quantitative, Ordinal, Nominal
Method	How measured (optional)

Batch Lookup

Look up multiple LOINC codes in a single request (up to 100):

Look up multiple lab tests

Request

Node.js

import { Fhirfly } from "@fhirfly-io/terminology";

const client = new Fhirfly({ apiKey: "YOUR_API_KEY" });

const result = await client.loinc.lookupMany(["2339-0","718-7","2160-0"]);
console.log(result.data.results);

Response

JSON

{
  "count": 3,
  "results": [
    {
      "input": "2339-0",
      "code": "2339-0",
      "status": "ok",
      "data": {
        "display_name": "Glucose, Blood",
        "class": "CHEM"
      }
    },
    {
      "input": "718-7",
      "code": "718-7",
      "status": "ok",
      "data": {
        "display_name": "Hemoglobin",
        "class": "HEM/BC"
      }
    },
    {
      "input": "2160-0",
      "code": "2160-0",
      "status": "ok",
      "data": {
        "display_name": "Creatinine, Serum/Plasma",
        "class": "CHEM"
      }
    }
  ],
  "meta": {
    "legal": {
      "license": "Regenstrief Institute"
    }
  }
}

Batch with `shape=full`

When using shape=full on batch requests, the response includes meta.source with provenance information:

POST /v1/loinc/_batch?shape=full

{
  "count": 3,
  "results": [
    {
      "input": "2339-0",
      "code": "2339-0",
      "status": "ok",
      "data": { "display_name": "Glucose, Blood", "class": "CHEM" }
    }
  ],
  "meta": {
    "source": {
      "name": "LOINC",
      "url": "https://loinc.org/",
      "version": "2.78",
      "fhirfly_updated_at": "2026-03-01T03:00:00Z"
    },
    "legal": {
      "license": "Regenstrief Institute",
      "attribution_required": true,
      "terms_of_use": "https://loinc.org/license/"
    }
  }
}

Response Shapes

Control the level of detail in responses with the shape query parameter:

Shape	Description
`compact`	Code, display_name, shortname, class, component
`standard`	+ long_name, parts, status, units, fhir_coding
`full`	+ version info, ranks, source_org

# Minimal data
GET /v1/loinc/2339-0?shape=compact

# Standard data (default)
GET /v1/loinc/2339-0?shape=standard

# Full data with provenance
GET /v1/loinc/2339-0?shape=full

See Response Shapes for field details.

License Notice

LOINC data requires attribution. See the meta.legal field in responses for citation requirements.

Required Scopes

loinc.read - Single and batch lookups