Query a FHIR R4 server using GraphQL to retrieve a patient with selected fields from nested resources in a single request, reducing over-fetching compared to REST
domain: hl7.org/fhir/R4 · 5 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
POST a GraphQL query to the FHIR server's /\$graphql endpoint with Content-Type: application/json and a query field containing the GraphQL document
Write a query that selects Patient.id, Patient.name, and nested MedicationRequestList filtered by patient and status=active, requesting only the medication and dosage fields
Handle the response data object which mirrors the FHIR resource structure; nested list results appear under resource type + List suffix conventions
Use GraphQL variables to parameterize the patient ID rather than embedding it as a string literal in the query
Parse errors from the errors array in the response independently from data; a partial success may return both data and errors
Known gotchas
FHIR GraphQL support is optional and not universally implemented; verify the CapabilityStatement lists the graphql operation or test the endpoint before building a production dependency
FHIR GraphQL field names follow FHIR JSON property names exactly, including camelCase; using snake_case or mismatched names returns null fields without an error
Search arguments in FHIR GraphQL use the same parameter names as REST search (e.g., patient, status) but as GraphQL argument syntax, not query string; incorrect syntax silently returns empty lists on some servers
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