Frequency Registry 33 dosing frequency codes across 7 categories.

Source tiers: S1 HL7 v3-GTSAbbreviation S2 NHS Convention S3 Clinical Extension

Regular Frequencies

Standard daily dosing patterns with fixed administration times.

Code	Display	Aliases	Freq	Interval	Default Times	Latin	Source	FHIR
`OD`	Once daily	QD, od, o.d., q.d., once daily, daily	1/d	24h	08:00	omni die	S1 S2	`QD`
`BD`	Twice daily	BID, bd, b.d., b.i.d., twice daily	2/d	12h	08:00, 20:00	bis in die	S1 S2	`BID`
`TDS`	Three times daily	TID, tds, t.d.s., t.i.d., three times daily	3/d	8h	08:00, 14:00, 20:00	ter die sumendus	S1 S2	`TID`
`QDS`	Four times daily	QID, qds, q.d.s., q.i.d., four times daily	4/d	6h	06:00, 12:00, 18:00, 22:00	quater die sumendus	S1 S2	`QID`
`5X_DAILY`	Five times daily	5x daily, five times daily	5/d	~4.8h	06:00, 10:00, 14:00, 18:00, 22:00	—	S3	—

Locale note: OD/BD/TDS/QDS are en-GB (NHS) canonical forms. QD/BID/TID/QID are en-US equivalents from the HL7 GTS standard. Both are valid aliases.

Interval-Based Frequencies

Fixed-interval dosing. Codes with empty default times use rolling schedules from the start time.

Code	Display	Aliases	Interval	Default Times	Source	FHIR
`Q1H`	Every 1 hour	every 1 hour, hourly, q1h	1h	rolling	S1 S2	`Q1H`
`Q2H`	Every 2 hours	every 2 hours, q2h	2h	rolling	S1 S2	—
`Q4H`	Every 4 hours	every 4 hours, q4h	4h	06:00, 10:00, 14:00, 18:00, 22:00, 02:00	S1 S2	`Q4H`
`Q6H`	Every 6 hours	every 6 hours, q6h	6h	06:00, 12:00, 18:00, 00:00	S1 S2	`Q6H`
`Q8H`	Every 8 hours	every 8 hours, q8h	8h	06:00, 14:00, 22:00	S1 S2	—
`Q12H`	Every 12 hours	every 12 hours, q12h	12h	08:00, 20:00	S3	—
`Q24H`	Every 24 hours	every 24 hours, q24h	24h	08:00	S3	—
`Q36H`	Every 36 hours	every 36 hours, q36h	36h	rolling	S3	—
`Q48H`	Every 48 hours	every 48 hours, alternate days, q48h	48h	08:00	S3	—
`Q72H`	Every 72 hours	every 72 hours, q72h	72h	rolling	S3	—

Time-of-Day Frequencies

Doses tied to a specific time of day rather than an interval.

Code	Display	Aliases	Default Time	Latin	Source	FHIR
`MANE`	In the morning	mane, morning, AM, in the morning	08:00	mane	S1 S2	`AM`
`NOCTE`	At night	nocte, ON, at night, at bedtime, HS	22:00	nocte	S1 S2	—
`MIDI`	At midday	midday, noon, lunchtime	12:00	—	S3	—
`AM_PM`	Morning and evening	morning and evening, AM+PM	08:00, 20:00	—	S3	—

Meal-Relative Frequencies

These are modifiers — they combine with a base frequency. “TDS AC” = three times daily before meals.

Code	Display	Aliases	Relation	Latin	Source
`AC`	Before meals	a.c., before food, before meals, ante cibum	Before	ante cibum	S2
`PC`	After meals	p.c., after food, after meals, post cibum	After	post cibum	S2
`CC`	With meals	c.c., with food, with meals, cum cibo	With	cum cibo	S3
`AC_HS`	Before meals and at bedtime	before meals and at bedtime, AC+HS	Before + bedtime	—	S3

As-Needed (PRN) Frequencies

Doses taken when required, optionally with minimum interval and daily maximum constraints.

Code	Display	Aliases	Max/Day	Min Interval	Latin	Source
`PRN`	As needed	p.r.n., as needed, as required, when required, pro re nata	configurable	—	pro re nata	S2
`PRN_Q4H`	As needed, max every 4 hours	PRN every 4 hours, as needed max every 4 hours, p.r.n. q4h	6	4h	—	S3
`PRN_Q6H`	As needed, max every 6 hours	PRN every 6 hours, as needed max every 6 hours, p.r.n. q6h	4	6h	—	S3
`SOS`	If needed (single use)	s.o.s., if needed, si opus sit	1	—	si opus sit	S3

One-Off Frequencies

Single-administration doses.

Code	Display	Aliases	Count	Latin	Source
`STAT`	Immediately	stat, immediately, now, statim	1	statim	S2
`ONCE`	Single dose	single dose, one-off, ×1, x1	1	—	S3

Extended Interval Frequencies

Multi-day, weekly, or monthly dosing schedules.

Code	Display	Aliases	Period	Default Time	Source	FHIR
`QOD`	Every other day	every other day, alternate days, on alternate days, qod	2 days	08:00	S1 S2	`QOD`
`WEEKLY`	Once weekly	once a week, weekly, every week, Q1W	1 week	08:00	S1	—
`BIWEEKLY`	Every 2 weeks	every 2 weeks, fortnightly, Q2W	2 weeks	08:00	S3	—
`MONTHLY`	Once monthly	once a month, monthly, Q1M	1 month	08:00	S1	—