Implementation guide for interoperable medicines

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

Timing Elements: when, offset, dayOfWeek, timeOfDay, event and code

A dosage instruction can be tied to the specific days, dates and times, plus life events related to eating or sleeping.

Sub-elements: when and offset

The when element ties to the regular life events of sleeping and eating, for example:

  • C = event occurs at a meal
  • WAKE = event occurs [offset] after waking

An offset allows the event to be tied x minutes before or after.

The offset is an unsigned integer value so different codes within the when value-set are used to define before or after.

Note: Guidance for the use of timing codes for event occurs before/at/after a meal is currently under review and may be subject to change.

Event occurs at breakfast

<timing>
    <repeat>
        <when value="CM"/>
    </repeat>
</timing>

Event occurs at 1 hour before breakfast

<timing>
    <repeat>
        <when value="ACM"/>
        <offset value="60" />
    </repeat>
</timing>

Event occurs at 1 hour after breakfast

<timing>
    <repeat>
        <when value="PCM"/>
        <offset value="60" />
    </repeat>
</timing>

Sub-elements: dayOfWeek and timeOfDay

A dosage instruction can specify days of a week and/or specific times within a day for administration.

on Monday and Thursday at 09:00 and 15:00

<timing>
    <repeat>
        <dayOfWeek value="mon" />
        <dayOfWeek value="thu" />
        <timeOfDay value="09:00:00" />
        <timeOfDay value="15:00:00" />
    </repeat>
</timing>
FHIR Inconsistency: The FHIR R4 standard includes a comment that the elements frequency, period and when cannot be used with dayOfWeek and/or timeOfDay. However the rule defined in FHIR R4 only applies to when plus an example exists in the FHIR standard for "Daily at 10:00". Within FHIR R5, the comment has been amended to only apply to when. This guidance is based on the rules defined in FHIR R4 and latest ballot release of FHIR R5.

Daily at 10:00

<timing>
    <repeat>
        <frequency value="1"/>
        <period value="1"/>
        <periodUnit value="d"/>
        <timeOfDay value="10:00:00" />  
    </repeat>
</timing>

Sub-element: event

A dosage instruction can specify specific dates and times for administration.

on 1st Nov 2019

<timing>
    <event value="2019-11-01" />
</timing>

on 1st Nov 2019 at 10:30 and again on 1st Dec 2019 at 22:30

<timing>
    <event value="2019-11-01T10:30" />
    <event value="2019-12-01T22:30" />
</timing>

Sub-element: code

Allows a code, often a Latin abbreviation, for a timing schedule to be specified, for example: BID = twice a day

Note: It is recommended that such codes are not used when the rest of the Dosage structure is supported by the system. Use the structures like frequency and period instead, so that a timing schedule can be computable.
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