Ever seen a prescription like this … 2mL a.c. omni mane ? Or 5mL q.3h ? Medical and herbal dosage terminology is often derived from old Latin, however it is still commonly used. Here is a list of the most common abbreviations and how to decipher them.
CAUTION: Remember clarity is essential – if you are writing a prescription which somebody else may view and not understand, it is far better to forgo the abbreviations and write it longhand. It might be more tedious, but one of the biggest causes of adverse reactions to medicines is incorrect dosage, so it is better to avoid confusion and err on the side of clarity.
UPDATE 7 August 2015: clarification of the once daily abbreviations
| ABBREVIATION | ENGLISH | LATIN |
|---|---|---|
| Quantity | ||
| t | a drop | gutta |
| gtt | drops | guttae |
| mL | millilitres | |
| Dosing Frequency (Hourly) | ||
| alt. hor. | alternate hours | alternis horis |
| q.h. | every hour | quaque hora |
| q. 2 h. | every 2 hours | quaque 2 hora |
| q. 3 h. | every 3 hours | quaque 3 hora |
| q. 4 h. | every 4 hours | quaque 4 hora |
| Dosing Frequency (Daily) | ||
| o.d. | every day (preferred in the UK as opposed to q.d.) | omni die |
| q.d. or q.1.d. | every day | quaque die |
| alt dieb. | every other day | alternis diebus |
| b.d. , b.i.d. | twice a day | bis in die |
| b.i.n. | twice a night | bis in noctis |
| t.d.s. | three times a day | ter die sumendum |
| t.i.d. | three times a day | ter in die |
| q.d.s. | four times daily | quater die sumendum |
| q.i.d. | four times a day | quater in die |
| Dosing Frequency (Specific Time) | ||
| a.c. | before food | ante cibum |
| p.c. | after food | post cibum |
| alt. noct. | alternate nights | alternis noctes |
| h.d. | at bedtime | hora decubitus |
| mane | in the morning | mane |
| o.m. | every morning | omni mane |
| noct. | in the night | nocte |
| o.n. | every night | omni nocte |
| non rep. | not to be repeated | non repetatur |
| p.r.n. | whenever necessary | pro re nata |
| stat. | at once | statim |