Dose syntax implementation guidance for FHIR STU3

This guidance is under active development by NHS Digital and content may be added or updated on a regular basis.

Element: rate

A rate-based quantity, such as 30 ml per hour, can be expressed as a rateRatio with coded numerator and denominator values.

Where the unit of measure for the ratio is defined within UCUM (see Common UCUM Units), for example, “milliliter per hour”, it can also be expressed using the simpler rateQuantity structure.

Dosage.rateRatio

Where the rate is expressed as coded numerator and denominator values.

at a rate of 30ml/hour using rateRatio

<rateRatio>
	<numerator>
		<value value="30"/>
		<unit value="millilitre"/>
		<system value="http://unitsofmeasure.org"/>
		<code value="mL"/>
	</numerator>
	<denominator>
		<value value="1"/>
		<unit value="hour"/>
		<system value="http://unitsofmeasure.org"/>
		<code value="h"/>
	</denominator>
</rateRatio>

Dosage.rateQuantity

Where the unit of measure applicable to a rate is defined within UCUM which is mathematically equivalent to defining the rate using the more complex rateRatio structure.

at a rate of 30ml/hour using rateQuantity

<rateQuantity>
	<value value="30"/>
	<unit value="milliliters per hour"/>
	<system value="http://unitsofmeasure.org"/>
	<code value="mL/h"/>
</rateQuantity>

at a rate of 1mcg/kg/hour using rateQuantity

<rateQuantity>
	<value value="1"/>
	<unit value="microgram per kilogram per hour"/>
	<system value="http://unitsofmeasure.org"/>
	<code value="ug/kg/h"/>
</rateQuantity>

Dosage.rateRange

Where the unit of measure applicable to a rate range is defined within UCUM the rateRange structure can be used.

give at 1-2 litres per minute using rateRange

<rateRange>
	<low>
		<value value="1"/>
		<unit value="liter per minute"/>
		<system value="http://unitsofmeasure.org"/>
		<code value="L/min"/>
	</low>
	<high>
		<value value="2"/>
		<unit value="liter per minute"/>
		<system value="http://unitsofmeasure.org"/>
		<code value="L/min"/>
	</high>
</rateRange>
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