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Medication Abbreviations, in Plain English

Prescription labels often use short codes that come from Latin. Here is what the common ones mean, with notes on the ones that are easy to misread. Use “Make a schedule” to turn a frequency into a printable chart.

Most looked up:BIDTIDQIDPRNQHSPO

How often to take it

QD / daily
Once a day
QD is on the Joint Commission “Do Not Use” list because it can be misread as QID. Prescribers are asked to write “daily”.Make a schedule
BID
Twice a day
From the Latin bis in die.Make a scheduleRead more
TID
Three times a day
From the Latin ter in die.Make a schedule
QID
Four times a day
From the Latin quater in die.Make a schedule
QOD
Every other day
On the “Do Not Use” list because it can be misread as QD or QID. Prescribers should write “every other day”.
QAM
Every morning
Make a schedule
QHS / HS
At bedtime
HS can also mean “half-strength”, so many labels now say “at bedtime” instead.Make a schedule
Q4H
Every 4 hours
Doses are spread evenly, including at night if the label says so.
Q6H
Every 6 hours
Q8H
Every 8 hours
Q12H
Every 12 hours
Doses are kept 12 hours apart. Close to BID, but the timing is stricter.
PRN
As needed
From the Latin pro re nata. The label should say what it is for and the most you can take.Make a schedule
STAT
Right away
Mostly used in hospitals.
AC
Before meals
From the Latin ante cibum.
PC
After meals
From the Latin post cibum.

How to take it

PO
By mouth
From the Latin per os.
SL
Under the tongue
Let it dissolve; do not swallow it whole.
TOP
On the skin
Also written “topical”.
INH
Breathed in
Used for inhalers and nebulizers.
PR
Rectally
Subcut
Injected under the skin
ISMP recommends “subcut” or “subcutaneously”; SC, SQ and sub q are easy to misread.
IM
Injected into a muscle
IV
Into a vein
OD / OS / OU
Right eye / left eye / both eyes
Easy to confuse with AD / AS / AU (right ear, left ear, both ears). Ask your pharmacist if unsure.
gtt
Drops
From the Latin guttae.

Amounts and other terms

tab
Tablet
cap
Capsule
mg
Milligram
mcg
Microgram
Written “mcg” rather than “µg”, which can be misread as mg.
mL
Milliliter
Use the cup or syringe that came with the medicine, not a kitchen spoon.
NPO
Nothing by mouth
Often used before surgery or a test.
Sig.
Directions
On a prescription, what follows “Sig.” is how to take the medicine.

Abbreviations prescribers are asked not to use

Some abbreviations are easy to misread, so safety groups ask prescribers to write the words out instead. If your label uses one of these and you are not sure what it means, ask your pharmacist.

  • U or IU: write “units”
  • QD: write “daily”
  • QOD: write “every other day”
  • MS, MSO4, MgSO4: write the full drug name
  • Trailing zeros (1.0 mg) or missing leading zeros (.5 mg): write 1 mg and 0.5 mg

Source: ISMP List of Error-Prone Abbreviations, Symbols, and Dose Designations, which also marks the items on The Joint Commission’s “Do Not Use” list.

Questions people ask

Short, plain answers. Still unsure? Ask your pharmacist.

Related templates

Sources

Written by the Medication List Template team

Last updated October 28, 2026

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Medication List Template helps you organize your medicines. It is not medical advice. Always follow your doctor's or pharmacist's instructions.