The RXO segment carries the original pharmacy or treatment order as the prescriber wrote it: what to give, how much, in what form, whether substitutions are allowed, and how much to dispense. It is the prescriber's intent — the unverified, un-encoded request that a pharmacist later turns into an encoded RXE. Where ORC says this is an order, RXO says what the medication order actually is.
Purpose
RXO records the requested give code (the drug), the give amount range and units, the dosage form, provider instructions, substitution permission, and the requested dispense quantity, units, and refills. It represents the order as authored, before pharmacy verification or encoding. Strength, indication, and rate fields let the prescriber describe the medication in clinical terms rather than dispensing terms.
Used in
RXO appears in pharmacy/treatment order messages — RDE (pharmacy/treatment encoded order), OMP (pharmacy/treatment order), and the general order message ORM. It is the order detail that follows an ORC and is typically paired with an RXR route segment. See ORM.
Field-by-field reference
Source: the Vorro HL7 segment database (extracted from the official v2-to-FHIR IG). R = required (cardinality min ≥ 1). Repeat = field may repeat. Length is not carried by the FHIR source and is shown as —.
| Seq | Name | Data Type | Length | Req | Repeat | Table # | Description |
|---|---|---|---|---|---|---|---|
| RXO-1 | Requested Give Code | CWE | — | O | — | — | The drug or treatment ordered; the core item. |
| RXO-2 | Requested Give Amount - Minimum | NM | — | O | — | — | Minimum dose to give per administration. |
| RXO-3 | Requested Give Amount - Maximum | NM | — | O | — | — | Maximum dose, for a range order. |
| RXO-4 | Requested Give Units | CWE | — | O | — | — | Units for the give amount (mg, mL). |
| RXO-5 | Requested Dosage Form | CWE | — | O | — | — | Physical form: tablet, capsule, solution. |
| RXO-6 | Provider's Pharmacy/Treatment Instructions | CWE | — | O | Y | — | Coded instructions to the pharmacy. |
| RXO-7 | Provider's Administration Instructions | CWE | — | O | Y | — | Coded instructions for administration. |
| RXO-8 | Deliver-To Location | CM | — | O | — | — | Where the medication should be delivered. |
| RXO-9 | Allow Substitutions | ID | — | O | — | HL70161 | Whether generic substitution is permitted. |
| RXO-10 | Requested Dispense Code | CWE | — | O | — | — | Coded item to dispense, if different. |
| RXO-11 | Requested Dispense Amount | NM | — | O | — | — | Quantity to dispense. |
| RXO-12 | Requested Dispense Units | CWE | — | O | — | — | Units for the dispense quantity. |
| RXO-13 | Number Of Refills | NM | — | O | — | — | Authorized number of refills. |
| RXO-14 | Ordering Provider's DEA Number | XCN | — | O | Y | — | Prescriber's DEA number for controlled drugs. |
| RXO-15 | Pharmacist/Treatment Supplier's Verifier ID | XCN | — | O | Y | — | Verifying pharmacist or supplier identifier. |
| RXO-16 | Needs Human Review | ID | — | O | — | — | Flags the order for manual review. |
| RXO-17 | Requested Give Per (Time Unit) | ST | — | O | — | — | Time unit the give amount applies to. |
| RXO-18 | Requested Give Strength | NM | — | O | — | — | Strength value of the medication. |
| RXO-19 | Requested Give Strength Units | CWE | — | O | — | — | Units for the give strength. |
| RXO-20 | Indication | CWE | — | O | Y | — | Clinical reason the medication is ordered. |
| RXO-21 | Requested Give Rate Amount | ST | — | O | — | — | Rate at which to administer. |
| RXO-22 | Requested Give Rate Units | CWE | — | O | — | — | Units for the give rate. |
| RXO-23 | Total Daily Dose | CQ | — | O | — | — | Total dose per day (carried as RXE-19). |
| RXO-24 | Supplementary Code | CWE | — | O | Y | — | Additional codes such as billing or NDC. |
| RXO-25 | Requested Drug Strength Volume | NM | — | O | — | — | Volume the strength is expressed per. |
| RXO-26 | Requested Drug Strength Volume Units | CWE | — | O | — | — | Units for the strength volume. |
| RXO-27 | Pharmacy Order Type | ID | — | O | — | HL70480 | Medication, IV, or supply order type. |
| RXO-28 | Dispensing Interval | NM | — | O | — | — | Minimum interval between dispenses. |
| RXO-29 | Medication Instance Identifier | EI | — | O | — | — | Identifier for this medication instance. |
| RXO-30 | Segment Instance Identifier | EI | — | O | — | — | Identifier for this segment instance. |
| RXO-31 | Mood Code | CNE | — | O | — | HL70725 | Mood of the order (e.g. request). |
| RXO-32 | Dispensing Pharmacy | CWE | — | O | — | — | Pharmacy responsible for dispensing. |
| RXO-33 | Dispensing Pharmacy Address | XAD | — | O | — | — | Address of the dispensing pharmacy. |
| RXO-34 | Deliver-to Patient Location | PL | — | O | — | — | Patient location for delivery. |
| RXO-35 | Deliver-to Address | XAD | — | O | — | — | Address to deliver the medication to. |
| RXO-36 | Pharmacy Phone Number | XTN | — | O | Y | — | Contact phone number for the pharmacy. |
Most-used fields
- RXO-1 Requested Give Code is the heart of the order — the drug or treatment being requested, and the field every downstream system reads first.
- RXO-2/RXO-3 Requested Give Amount Minimum/Maximum with RXO-4 Requested Give Units express the dose (a single value or a range).
- RXO-5 Requested Dosage Form distinguishes tablet, capsule, or solution and drives the referenced Medication.doseForm.
- RXO-9 Allow Substitutions tells the pharmacy whether a generic may be dispensed.
- RXO-11/RXO-12 Requested Dispense Amount and Units plus RXO-13 Number Of Refills define what and how much to dispense.
Version differences (2.3 to 2.8.2)
- 2.3/2.4: core give/dispense fields (RXO-1 through RXO-13) are stable; coded fields use
CE. - 2.5: coded fields move from
CEtowardCWE; strength and rate fields (RXO-18 through RXO-22) clarified. - 2.7+: trailing fields RXO-25 through RXO-36 (strength volume, pharmacy order type, mood code, dispensing pharmacy and delivery details) were added.
- Receivers built for 2.3 ignore the trailing fields they do not recognize.
Common mistakes
- Confusing the give amount (RXO-2/3, per administration) with the dispense amount (RXO-11, total to supply).
- Treating RXO-1 as free text and losing the coding system that identifies the drug.
- Dropping RXO-9 Allow Substitutions, forcing the pharmacy to guess substitution permission.
- Reading only the first repetition of RXO-6/RXO-7 when several instruction lines are present.
- Putting strength in the give units field instead of RXO-18/RXO-19.
Examples
Minimal valid RXO (just the requested give code):
RXO|0009-0058-01^Lisinopril 10 mg tablet^NDC
Fully-populated RXO (oral medication order):
RXO|0009-0058-01^Lisinopril 10 mg tablet^NDC|10|10|mg^milligram^UCUM|TAB^tablet^HL70484||||N^No substitution^HL70161|0009-0058-01^Lisinopril 10 mg tablet^NDC|30|TAB^tablet^HL70484|3|AA1234567^SMITH^JANE^A^^^MD||||10|mg^milligram^UCUM|I10^Essential hypertension^ICD10
Annotated breakdown of the fully-populated example (selected fields):
RXO ← segment ID
0009-0058-01^Lisinopril 10 mg tablet^NDC ← RXO-1 Requested Give Code
10 ← RXO-2 Requested Give Amount - Minimum
10 ← RXO-3 Requested Give Amount - Maximum
mg^milligram^UCUM ← RXO-4 Requested Give Units
TAB^tablet^HL70484 ← RXO-5 Requested Dosage Form
N^No substitution^HL70161 ← RXO-9 Allow Substitutions
30 ← RXO-11 Requested Dispense Amount
TAB^tablet^HL70484 ← RXO-12 Requested Dispense Units
3 ← RXO-13 Number Of Refills
AA1234567^SMITH^JANE^A^^^MD ← RXO-14 Ordering Provider's DEA Number
10 ← RXO-18 Requested Give Strength
mg^milligram^UCUM ← RXO-19 Requested Give Strength Units
I10^Essential hypertension^ICD10 ← RXO-20 Indication
In-context inside an ORM^O01 (new pharmacy order, RXO with ORC and RXR):
MSH|^~&|CPOE|MERCYGEN|PHARM|MERCYGEN|20260609120000||ORM^O01^ORM_O01|MSG201|P|2.5.1
PID|1||MR12345^^^MERCYGEN^MR||DOE^JOHN^Q||19800101|M
ORC|NW|ORD5001^CPOE|||||||20260609120000|||1234^SMITH^JANE^A^^^MD
RXO|0009-0058-01^Lisinopril 10 mg tablet^NDC|10|10|mg^milligram^UCUM|TAB^tablet^HL70484||||N^No substitution^HL70161|||30|TAB^tablet^HL70484|3
RXR|PO^Oral^HL70162
In-context inside an RDE^O11 (encoded order, original RXO retained with ORC and RXR):
MSH|^~&|PHARM|MERCYGEN|EHR|MERCYGEN|20260609123000||RDE^O11^RDE_O11|MSG202|P|2.5.1
PID|1||MR12345^^^MERCYGEN^MR||DOE^JOHN^Q||19800101|M
ORC|NW|ORD5001^CPOE|RX9001^PHARM||||||20260609123000|||1234^SMITH^JANE^A^^^MD
RXO|0009-0058-01^Lisinopril 10 mg tablet^NDC|10|10|mg^milligram^UCUM|TAB^tablet^HL70484||||N^No substitution^HL70161|||30|TAB^tablet^HL70484|3
RXR|PO^Oral^HL70162
FHIR mapping
Primary target resource: MedicationRequest. RXO also populates the referenced Medication resource (code, dose form, ingredient strength) and the request's dispenseRequest. The order itself maps to MedicationRequest.intent = "original-order". Official ConceptMap: RXO to MedicationRequest.
Key MedicationRequest mappings:
| RXO field | FHIR target (MedicationRequest) |
|---|---|
| RXO (segment) | intent = original-order |
| RXO-1 Requested Give Code | medication (Medication.code) |
| RXO-2 Give Amount Minimum | dosageInstruction.doseAndRate[1].doseRange.low.value (type ordered) |
| RXO-3 Give Amount Maximum | dosageInstruction.doseAndRate[1].doseRange.high.value |
| RXO-4 Give Units | dosageInstruction.doseAndRate[1].doseRange.low/high.code + .unit |
| RXO-5 Requested Dosage Form | medication (Medication.doseForm) |
| RXO-9 Allow Substitutions | substitution.allowedCodeableConcept |
| RXO-11 Requested Dispense Amount | dispenseRequest.quantity.value |
| RXO-12 Requested Dispense Units | dispenseRequest.quantity.code + .unit |
| RXO-13 Number Of Refills | dispenseRequest.numberOfRepeatsAllowed |
| RXO-14 Ordering Provider's DEA Number | requester (Practitioner) |
| RXO-18 Requested Give Strength | medicationReference (Medication.ingredient.strength.numerator.value) |
| RXO-19 Give Strength Units | medicationReference (Medication.ingredient.strength.numerator.code + .unit) |
| RXO-23 Total Daily Dose (RXE-19) | dosageInstruction.maxDosePerPeriod (numerator + denominator 1/d) |
| RXO-25 Drug Strength Volume | medicationReference (Medication.ingredient.strength.denominator.value) |
| RXO-26 Drug Strength Volume Units | medicationReference (Medication.ingredient.strength.denominator.code + .unit) |
Fields without a published MedicationRequest mapping in the source — RXO-6, RXO-7, RXO-8, RXO-10, RXO-15, RXO-16, RXO-17, RXO-20, RXO-21, RXO-22, RXO-24, and RXO-27 through RXO-36 — are instructions, delivery, and administrative details not represented on the curated ConceptMap rows.
Engine considerations
- RXO has no standard-required fields, but real pharmacy interfaces require RXO-1 plus the give amount/units and dispense amount/units for a usable order.
- Keep the give amount (RXO-2/3) and dispense amount (RXO-11) distinct — they map to different FHIR structures (
doseRangevsdispenseRequest.quantity). - Preserve the coding system component of RXO-1, RXO-4, RXO-5, and RXO-12 so units and drugs round-trip to UCUM/NDC.
- Repeating fields (RXO-6/7/14/15/20/24/36) must be preserved as arrays.
How Vorro parses and produces RXO
Vorro maps RXO-1 to the referenced Medication.code and builds MedicationRequest with intent = original-order, decomposing give amount/units into dosageInstruction.doseAndRate and dispense amount/units/refills into dispenseRequest. Strength fields (RXO-18/19/25/26) populate Medication.ingredient.strength, substitution permission (RXO-9) maps to substitution.allowedCodeableConcept, and the DEA prescriber (RXO-14) becomes the requester per the official ConceptMap. Repeating instruction and indication fields are preserved as arrays.
Related pages
- RXR — the route segment that pairs with RXO.
- RXE — the pharmacy-encoded order RXO is turned into.
- ORM messages — where RXO carries the pharmacy/treatment order detail.
