Medical terminology API: LOINC, SNOMED, ICD-10, RxNorm
Where to look up each medical code system for free, how codes appear in FHIR, and what Anpheros includes (a small LOINC/ATC subset and symptom concepts) — honestly scoped.
A medical terminology API lets software search and look up standard medical codes — LOINC for tests and measurements, SNOMED CT for clinical terms, ICD-10 for diagnoses, RxNorm and ATC for medicines — so data from different sources means the same thing. Each code system has its own owner, licence and lookup service, and most are free. This page lists where to look up each one, how they appear in FHIR, and what Anpheros includes so your app can store coded data without running a terminology server.
Where to look up each code system
LOINC — lab tests and measurementsloinc.org search; FHIR terminology server fhir.loinc.org (free LOINC account)
ICD-10-CM — diagnoses (US)NLM Clinical Tables API, free and keyless
Every coded element in FHIR is a CodeableConcept: one or more codings, each with a system URI and a code, plus the original text.
Code system
FHIR system URI
LOINC
http://loinc.org
SNOMED CT
http://snomed.info/sct
ICD-10
http://hl7.org/fhir/sid/icd-10
ICD-10-CM
http://hl7.org/fhir/sid/icd-10-cm
RxNorm
http://www.nlm.nih.gov/research/umls/rxnorm
ATC
http://www.whocc.no/atc
UCUM units
http://unitsofmeasure.org
What Anpheros includes
A bundled LOINC and ATC subset for the codes an app uses most (vital signs, common laboratory tests, common medicine classes): GET /v1/terminology/loinc?q=glucose and GET /v1/terminology/atc/{code}. It is a small subset, not a full terminology server; a code outside it may still be stored.
Symptom concepts with ICD-10 mappings and labels in several languages: GET /v1/terminology/symptoms?q=headache.
Codes stored as written: any valid FHIR coding is kept, and the lab connector fills LOINC codes where it recognises the test.
A free FHIR R4 validator that checks structure and the value sets of common elements.
Frequently asked questions
Is there a free LOINC API?
Yes. LOINC provides a FHIR terminology server at fhir.loinc.org for registered users (registration is free), and the NLM Clinical Tables API offers a keyless LOINC search.
Is there a free ICD-10 API?
Yes. The NLM Clinical Tables API searches ICD-10-CM without a key, and the WHO ICD API covers ICD-10 and ICD-11 after free registration.
Do I need a licence for SNOMED CT?
In SNOMED International member countries (including the US and most of the EU) use is free under the national licence; elsewhere a licence is required. Check your country's National Release Centre.
Does Anpheros include a full terminology server?
No. It includes a small LOINC and ATC subset and a symptom knowledge base, and stores any valid code. For full lookups, use the official services above.
