Dose syntax implementation guidance for FHIR STU3

Levothyroxine 100mcg on one day alternating with 125mcg on another day

The dose should be 100mcg/125mcg, and it the label on the dispensed item for the patient will likely by a VTM such as:

Levothyroxine sodium 100mcg tablets - one to be taken daily and Levothyroxine sodium 25mcg tablets - one to be taken on alternate days

To account for this, the example below shows how to describe a dose instruction containing concurrent sequences.

<MedicationRequest xmlns="http://hl7.org/fhir">
    <id value="efaae147-81bb-4abd-b1d4-dd394a7ffc0c" />
    <contained>
        <Medication>
            <id value="med1" />
            <code>
                <coding>
                    <system value="http://snomed.info/sct" />
                    <code value="126202002" />
                    <display value="Levothyroxine sodium" />
                </coding>
            </code>
        </Medication>
    </contained>
    <status value="active" />
    <intent value="order" />
    <medicationReference>
        <reference value="#med1" />
    </medicationReference>
    <subject>
        <identifier>
            <system value="https://fhir.nhs.uk/Id/nhs-number" />
            <value value="4857773456" />
        </identifier>
    </subject>
    <dosageInstruction>
        <sequence value="1" />
        <timing>
            <repeat>
                <frequency value="1" />
                <period value="1" />
                <periodUnit value="d" />
            </repeat>
        </timing>
        <doseQuantity>
            <value value="100" />
            <unit value="microgram" />
            <system value="http://unitsofmeasure.org" />
            <code value="ug" />
        </doseQuantity>
    </dosageInstruction>
    <dosageInstruction>
        <sequence value="1" />
        <timing>
            <repeat>
                <frequency value="1" />
                <period value="2" />
                <periodUnit value="d" />
            </repeat>
        </timing>
        <doseQuantity>
            <value value="25" />
            <unit value="microgram" />
            <system value="http://unitsofmeasure.org" />
            <code value="ug" />
        </doseQuantity>
    </dosageInstruction>
</MedicationRequest>

{
    "resourceType": "MedicationRequest",
    "id": "efaae147-81bb-4abd-b1d4-dd394a7ffc0c",
    "contained":  [
        {
            "resourceType": "Medication",
            "id": "med1",
            "code": {
                "coding":  [
                    {
                        "system": "http://snomed.info/sct",
                        "code": "126202002",
                        "display": "Levothyroxine sodium"
                    }
                ]
            }
        }
    ],
    "status": "active",
    "intent": "order",
    "medicationReference": {
        "reference": "#med1"
    },
    "subject": {
        "identifier": {
            "system": "https://fhir.nhs.uk/Id/nhs-number",
            "value": "4857773456"
        }
    },
    "dosageInstruction":  [
        {
            "sequence": 1,
            "timing": {
                "repeat": {
                    "frequency": 1,
                    "period": 1,
                    "periodUnit": "d"
                }
            },
            "doseQuantity": {
                "value": 100,
                "unit": "microgram",
                "system": "http://unitsofmeasure.org",
                "code": "ug"
            }
        },
        {
            "sequence": 1,
            "timing": {
                "repeat": {
                    "frequency": 1,
                    "period": 2,
                    "periodUnit": "d"
                }
            },
            "doseQuantity": {
                "value": 25,
                "unit": "microgram",
                "system": "http://unitsofmeasure.org",
                "code": "ug"
            }
        }
    ]
}

MedicationRequest.id[0]	efaae147-81bb-4abd-b1d4-dd394a7ffc0c
MedicationRequest.contained[0].id[0]	med1
MedicationRequest.contained[0].code[0].coding[0].system[0]	http://snomed.info/sct
MedicationRequest.contained[0].code[0].coding[0].code[0]	126202002
MedicationRequest.contained[0].code[0].coding[0].display[0]	Levothyroxine sodium
MedicationRequest.status[0]	active
MedicationRequest.intent[0]	order
MedicationRequest.medication[0].reference[0]	#med1
MedicationRequest.subject[0].identifier[0].system[0]	https://fhir.nhs.uk/Id/nhs-number
MedicationRequest.subject[0].identifier[0].value[0]	4857773456
MedicationRequest.dosageInstruction[0].sequence[0]	1
MedicationRequest.dosageInstruction[0].timing[0].repeat[0].frequency[0]	1
MedicationRequest.dosageInstruction[0].timing[0].repeat[0].period[0]	1
MedicationRequest.dosageInstruction[0].timing[0].repeat[0].periodUnit[0]	d
MedicationRequest.dosageInstruction[0].dose[0].value[0]	100
MedicationRequest.dosageInstruction[0].dose[0].unit[0]	microgram
MedicationRequest.dosageInstruction[0].dose[0].system[0]	http://unitsofmeasure.org
MedicationRequest.dosageInstruction[0].dose[0].code[0]	ug
MedicationRequest.dosageInstruction[1].sequence[0]	1
MedicationRequest.dosageInstruction[1].timing[0].repeat[0].frequency[0]	1
MedicationRequest.dosageInstruction[1].timing[0].repeat[0].period[0]	2
MedicationRequest.dosageInstruction[1].timing[0].repeat[0].periodUnit[0]	d
MedicationRequest.dosageInstruction[1].dose[0].value[0]	25
MedicationRequest.dosageInstruction[1].dose[0].unit[0]	microgram
MedicationRequest.dosageInstruction[1].dose[0].system[0]	http://unitsofmeasure.org
MedicationRequest.dosageInstruction[1].dose[0].code[0]	ug

MedicationRequest

id : efaae147-81bb-4abd-b1d4-dd394a7ffc0c

contained

id : med1

code

coding

system : http://snomed.info/sct

code : 126202002

display : Levothyroxine sodium

status : active

intent : order

medication

reference : #med1

subject

identifier

system : https://fhir.nhs.uk/Id/nhs-number

value : 4857773456

dosageInstruction

sequence : 1

timing

repeat

frequency : 1

period : 1

periodUnit : d

dose

value : 100

unit : microgram

system : http://unitsofmeasure.org

code : ug