FHIR MedicationRequest, CarePlan, AllergyIntolerance, Procedure & Immunization: US Core Clinical Resources & RxNorm Guide

The FHIR MedicationRequest resource is the core clinical ordering resource in HL7 Fast Healthcare Interoperability Resources (FHIR) used to represent outpatient prescriptions, inpatient medication orders, and discharge medication lists. Together with CarePlan, AllergyIntolerance, Procedure, and Immunization, these five resources form the clinical treatment and safety backbone of the HL7 FHIR US Core Implementation Guide and ONC/ASTP USCDI interoperability mandates.

How Does FHIR MedicationRequest Represent Prescriptions and Inpatient Orders?

In HL7 FHIR R4 (https://hl7.org/fhir/R4/medicationrequest.html), MedicationRequest unifies all medication ordering workflows—including ambulatory e-prescriptions, hospital inpatient pharmacy orders (historically transmitted via HL7 v2 RDE^O11), and patient-reported active medications in US Core:

• status (1..1): Tracks the lifecycle state of the order (`active`, `on-hold`, `cancelled`, `completed`, `entered-in-error`, `stopped`, `draft`, `unknown`).
• intent (1..1): Distinguishes actionable clinical orders (`order`, `original-order`, `reflex-order`, `instance-order`) from care-planning proposals (`proposal`, `plan`) or historical patient reports (`filler-order`).
• category (0..*): Differentiates setting of care using codes from http://terminology.hl7.org/CodeSystem/medicationrequest-category: inpatient (hospital floor/ICU administrations), outpatient (clinic-administered medications), community (retail/mail-order pharmacy prescriptions), and discharge (hospital discharge medication reconciliation).
• dosageInstruction (0..*): Encodes structured sig instructions, including free-text sig (`dosageInstruction.text`), timing schedule (`timing.repeat`), route of administration (SNOMED CT route codes in `route`), and dose quantity (`doseAndRate.doseQuantity`).
• dispenseRequest (0..1): Populated on `community` prescriptions to specify `numberOfRepeatsAllowed` (refills), dispense `quantity`, `expectedSupplyDuration` (days supply), and target pharmacy (`performer`).

How Are RxNorm Codes Structured in FHIR Medication Resources?

Under the US Core MedicationRequest Profile, all medication concepts must be bound extensibly to the National Library of Medicine (NLM) RxNorm vocabulary (`http://www.nlm.nih.gov/research/umls/rxnorm`). FHIR R4 allows a MedicationRequest to identify the drug using a choice element (`medication[x]`):

1. Inline medicationCodeableConcept: The most common pattern for single-ingredient or standard commercial drugs, embedding the RxNorm Concept Unique Identifier (RxCUI) directly inside `MedicationRequest.medicationCodeableConcept`.
2. Referenced medicationReference: Points to a standalone or contained Medication resource when the order involves a multi-ingredient IV admixture (`Medication.ingredient`), custom compounding, or lot/manufacturer tracking (`Medication.batch`).

To prevent ambiguity between general drug classes and dispensable clinical products, US Core restricts RxNorm bindings to specific prescribable Term Types (TTYs): SCD (Semantic Clinical Drug, e.g.,RxCUI `860975` for Metformin hydrochloride 500 MG Extended Release Oral Tablet), SBD (Semantic Branded Drug), GPCK (Generic Pack), and BPCK (Branded Pack), while allowing ingredient-level codes (IN / MIN) primarily in `AllergyIntolerance` or historical compound records.

{
  "resourceType": "MedicationRequest",
  "id": "medrx-metformin-er",
  "status": "active",
  "intent": "order",
  "category": [
    {
      "coding": [
        {
          "system": "http://terminology.hl7.org/CodeSystem/medicationrequest-category",
          "code": "community",
          "display": "Community"
        }
      ]
    }
  ],
  "medicationCodeableConcept": {
    "coding": [
      {
        "system": "http://www.nlm.nih.gov/research/umls/rxnorm",
        "code": "860975",
        "display": "24 HR metformin hydrochloride 500 MG Extended Release Oral Tablet"
      }
    ],
    "text": "Metformin HCl 500 mg ER tablet"
  },
  "subject": {
    "reference": "Patient/patient-101"
  },
  "authoredOn": "2026-11-09T09:15:00Z",
  "requester": {
    "reference": "Practitioner/practitioner-22"
  },
  "dosageInstruction": [
    {
      "text": "Take 1 tablet by mouth once daily with evening meal",
      "timing": {
        "repeat": {
          "frequency": 1,
          "period": 1,
          "periodUnit": "d"
        }
      },
      "route": {
        "coding": [
          {
            "system": "http://snomed.info/sct",
            "code": "26643006",
            "display": "Oral route"
          }
        ]
      },
      "doseAndRate": [
        {
          "doseQuantity": {
            "value": 1,
            "unit": "tablet",
            "system": "http://unitsofmeasure.org",
            "code": "{tbl}"
          }
        }
      ]
    }
  ],
  "dispenseRequest": {
    "numberOfRepeatsAllowed": 3,
    "quantity": {
      "value": 90,
      "unit": "{tbl}"
    },
    "expectedSupplyDuration": {
      "value": 90,
      "unit": "days",
      "system": "http://unitsofmeasure.org",
      "code": "d"
    }
  }
}

How Does the FHIR CarePlan Resource Link Conditions, Goals, and Procedures?

While individual orders live in `MedicationRequest` or `ServiceRequest`, the FHIR CarePlan resource (https://hl7.org/fhir/R4/careplan.html) orchestrates longitudinal multidisciplinary care across problems, targets, and interventions:

• CarePlan.addresses (`0..* Reference(Condition)`): Links the care plan to the specific FHIR Condition problems or diagnoses being managed (for example, Type 2 Diabetes Mellitus or Congestive Heart Failure).
• CarePlan.goal (`0..* Reference(Goal)`): Points to measurable clinical targets stored in `Goal` resources (such as maintaining HbA1c < 7.0%).
• CarePlan.activity (`0..*`): Connects planned or completed interventions either via `activity.reference` (pointing to a `MedicationRequest`, `ServiceRequest`, or `NutritionOrder`) or via inline `activity.detail` structures linked to completed `Procedure` resources.

FHIR AllergyIntolerance, Procedure, and Immunization Profiles Compared

Alongside `MedicationRequest` and `CarePlan`, three additional US Core clinical resources complete the patient intervention and safety record:

FHIR R4 Resource	Clinical Scope	Core Status & Modifier Elements	Mandatory US Core Terminology Bindings
MedicationRequest	Inpatient/outpatient medication orders and prescriptions.	status, intent, category, dosageInstruction	RxNorm (http://www.nlm.nih.gov/research/umls/rxnorm)
CarePlan	Longitudinal care coordination plans and clinical narratives.	status, intent, category (assess-plan), text	LOINC / SNOMED CT care plan category codes
AllergyIntolerance	Immune-mediated allergies and non-immune adverse drug/food reactions.	clinicalStatus, verificationStatus, criticality, reaction.manifestation	RxNorm (drugs), SNOMED CT (substances & reactions), UNII
Procedure	Surgical, diagnostic, therapeutic, and counseling interventions performed.	status (completed, in-progress), code, performed[x]	SNOMED CT, CPT-4, HCPCS Level II, ICD-10-PCS
Immunization	Administered and historical vaccine records.	status (completed, not-done), vaccineCode, occurrence[x], lotNumber	CDC CVX (http://hl7.org/fhir/sid/cvx) and NDC

In EHR-to-EDC clinical trial data pipelines that transform FHIR bundles into CDISC SDTM submission datasets, `MedicationRequest` and `Immunization` map to the Concomitant Medications (`CM`) and Exposure (`EX`) domains, `Procedure` maps to the Procedures (`PR`) domain, and `AllergyIntolerance` reaction manifestations map to the Medical History (`MH`) or Adverse Events (`AE`) domains.

Frequently Asked Questions

How does FHIR MedicationRequest represent prescriptions and inpatient orders?

FHIR MedicationRequest uses the category element to distinguish outpatient retail prescriptions (community, which populate dispenseRequest with refills, quantity, and days supply) from hospital floor orders (inpatient) and discharge medication lists (discharge), while encoding structured sig details inside dosageInstruction.

How are RxNorm codes structured in FHIR medication resources?

Under the US Core MedicationRequest Profile, medications are coded using NLM RxNorm Concept Unique Identifiers (RxCUIs) under system URI http://www.nlm.nih.gov/research/umls/rxnorm—either inline via medicationCodeableConcept for standard Semantic Clinical Drugs (SCD) and Semantic Branded Drugs (SBD), or via medicationReference pointing to a Medication resource for multi-ingredient admixtures.

How does the FHIR CarePlan resource link Conditions, Goals, and Procedures?

The FHIR CarePlan resource links to the diagnoses it treats via CarePlan.addresses (referencing Condition), links to target clinical outcomes via CarePlan.goal (referencing Goal), and links to planned or completed interventions via CarePlan.activity.reference and CarePlan.activity.detail (referencing MedicationRequest, ServiceRequest, and Procedure).