Structured Sig API
Turn a prescription's free-text directions into a coded FHIR Dosage, with a review flag on anything a person should check.
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Request
POST /v1/fhir/r4/$structure-dosage
{
"resourceType": "Parameters",
"parameter": [
{ "name": "text",
"valueString": "Take 1 tablet by mouth daily" },
{ "name": "medication",
"valueCodeableConcept": { "coding": [{
"system": "http://www.nlm.nih.gov/research/umls/rxnorm",
"code": "311354",
"display": "lisinopril 5 MG Oral Tablet" }] } }
]
}Response
{
"resourceType": "Parameters",
"parameter": [{
"name": "dosage",
"valueDosage": {
"text": "Take 1 tablet by mouth daily",
"method": { "coding": [{
"system": "http://snomed.info/sct",
"code": "419652001", "display": "Take" }] },
"doseAndRate": [{ "doseQuantity": {
"value": 1, "unit": "Tablet",
"system": "http://unitsofmeasure.org", "code": "{tbl}" } }],
"route": { "coding": [{
"system": "http://snomed.info/sct",
"code": "26643006", "display": "Oral route" }] },
"timing": {
"repeat": { "frequency": 1, "period": 1, "periodUnit": "d" },
"code": { "coding": [{
"system": "http://snomed.info/sct",
"code": "69620002", "display": "Daily" }] } }
}
}]
}Directions in. A coded Dosage out.
The implementation guide's own example: a lisinopril tablet once a day, sent with its RxNorm code. The method, the dose, the route and the timing each come back coded, the directions are kept exactly as written, and nothing needs a person's review.
Both views show the same request and the same answer.
Directions sent
Take 1 tablet by mouth daily
lisinopril 5 MG Oral TabletRxNorm 311354
Structured
- Method
- TakeSNOMED CT 419652001
- Dose
- 1 tabletUCUM {tbl}
- Route
- Oral routeSNOMED CT 26643006NCIt C38288
- Timing
- once a daySNOMED CT 69620002HL7 QD
Nothing to review: the Dosage carries no review flag.
Engine 2026-10-30.v2 · vocabulary 2026-10-29.v1 · RxNorm release 10052026
What it does
- The directions kept exactly as written, in Dosage.text
- Dose and unit, route, method, timing and as needed, coded where the words support them
- Nothing guessed: an element the words do not support is left out
- A review flag on anything to check, with its published meaning and the words it is about
- With an RxNorm code, the dose's unit and the route checked against the product's dose form
- One sig per request, or many in one FHIR batch
Built on
Send the directions as written, and optionally the medication's RxNorm code, and get back a FHIR Dosage: the directions kept exactly in Dosage.text, each element the words support coded in SNOMED CT, NCIt or UCUM, and a review flag with a published meaning on anything to check. Send the directions, never a patient. Nothing a request carries is stored or logged.
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