Prescription Abbreviations

Medical prescriptions are written directions for the preparation and administration of a specific medication or remedy. Prescriptions specify a drug or therapy name, dose, form, delivery route, frequency, timing, and purpose. Additionally, they tell the pharmacist how much to dispense and how many refills are available.

The tables below summarize the most common abbreviations that appear on prescriptions.

  • Dangerous abbreviations: Numerous organizations advise medical professionals to avoid using abbreviations in prescriptions due to the risk that they may be misread or misunderstood. The symbol appears next to abbreviations that are particularly prone to causing prescription errors.
  • Abbreviation formatting: Abbreviation formatting varies widely by institution (e.g., PRN, prn, p.r.n.). For simplicity, the following tables use lowercase letters for Latin abbreviations and capital letters for English initialisms. Units of measurement are lowercase except when mixed case is recommended to help avoid prescription errors.

For a more comprehensive alphabetical list of abbreviations, consult OpenMD’s index of medical abbreviations.

(or Rx) is an abbreviation for “medical prescription”. It is derived from the Latin word recipe, meaning “take” (recipe is the imperative form of recipere, meaning “to take”). In the 16th century, the word was abbreviated as ℞\—the letter R with a line across the leg, which indicated that the R was an abbreviation.

Dose

The dose is the amount of a drug to be taken at one time. It is commonly specified in metric mass (e.g., milligrams) or international units (i.e., an agreed upon measure of biological effect for a given drug). Prescriptions are occasionally written using apothecary units, such as ounces and teaspoons.

Common abbreviations for medical doses:

Abbreviation Meaning
amt amount
cc milliliter (cubic centimeter)
dg decigram (0.1 gram)
dL deciliter (0.1 liter)
g, gm gram
gtt drop(s) (L. gutta or guttae)
IU international unit
mg milligram (0.001 gram)
mL milliliter (0.001 liter)
oz ounce
one tablet
ss one half (L. semis)
ss sliding scale (for insulin)
tbsp tablespoon
tsp teaspoon
U unit(s)

Form

Dosage form indicates the physical form of the medication, including active and inert ingredients. The form is selected to maximize drug efficacy and safety while allowing for easy administration. The form may be solid (e.g., tablets and capsules), semi-solid (e.g., ointments and creams), liquid (e.g., syrups and drops), or gas (e.g., inhalers and aerosols).

Abbreviation Meaning
cap capsule
comp compound
CR controlled-release
DR delayed-release
ER extended-release
lot lotion
neb nebulizer
oint ointment
pdr powder
pulv powder (L. pulvis)
tab tablet
ung ointment (L. unguentum)
XL extra-long (release)
XR extended-release

Delivery Route

The route of administration indicates where the drug is to be administered to the patient. The route may be enteral (ingested or rectal), parenteral (injected), inhaled (through the nose or mouth into the lungs), topical (onto the skin), ophthalmic (into the eye), or otic (into the ear).

Abbreviation Meaning
AA affected area
a.u. each ear, both ears (L. auris utraque)
ID intradermal
IM intramuscular
inf infusion
IN intranasal
IV intravenous
IVP intravenous push
IVPB intravenous piggyback
o.d. right eye (L. oculus dexter)
o.s. left eye (L. oculus sinister)
p.o. by mouth (L. per os)
PV, vag per vagina/vaginally
SL sublingual
SC, SQ subcutaneous
SUBQ, subcu subcutaneous

Sig

From the Latin signatura, meaning “let it be labeled”. This field includes instructions for delivery route and frequency.

Frequency

Frequency refers to when or how often a medication should be administered. This is typically expressed in terms of how many times per day, week, or month the medication should be taken.

Abbreviation Meaning
ad. lib. as desired, at liberty (L. ad libitum)
alt. dieb. every other day (L. alternis diebus)
alt. hor. alternate hours (L. alternis horis)
alt. noct. alternate nights (L. alternis noctibus)
b.i.d. twice a day (L. bis in die)
dieb. alt. every other day (L. diebus alternis)
o.d. once daily (L. omni die)
o.h. every hour (L. omni hora)
o.m. every morning (L. omni mane)
o.n. every night (L. omni nocte)
p.r.n. as desired/as required (L. pro re nata)
q1h every 1 hour
q2h every 2 hours
q3h every 3 hours
q4h every 4 hours
q6h every 6 hours
q.d. every day, once daily (L. quaque die)
q.h. every hour (L. quaque hora)
q.i.d. four times a day (L. quater in die)
q.o.d., q.a.d. every other day (L. quaque altera die)
q.p. as much as desired (L. quantum placeat)
q.s. a sufficient quantity (L. quantum sufficit)
q.v. as much as desired (L. quantum vis)
q.h.s. at bedtime (L. quaque hora somni)
t.i.d. three times a day (L. ter in die)

PRN

Medications are sometimes labeled PRN, which means “take as needed”. PRN is an abbreviation of the Latin phrase pro re nata, meaning “as the circumstance arises.” Medications with this label include analgesics, laxatives, and some anti-anxiety medications.

Timing and Administration

Instructions for the patient on when or how to take the medication. These instructions are usually intended to maximize the therapeutic effect of a medication or minimize side effects. Directions may include administering the drug at a certain time of day or at a specific time relative to the consumption of food.

Abbreviation Meaning
a.a. of each (L. ana ana)
ad up to (L. ad)
aq water (L. aqua)
DC, d/c discontinue
dil dilute
e.m.p. as directed (L. ex modo prescripto)
ft make, let it be made (L. fiat)
m.p. as directed (L. modo praescripto)
per for each
UD, UAD use as directed
ut. dict. as directed (L. ut dictum)
c.c. with food (L. cum cibos)
a.c. before meals (L. ante cibum)
a.m. morning, before noon (L. ante meridiem)
a.p. before meals (L. ante prandium)
h hour
h.s. bedtime (L. hora somni)
p.c. after meals (L. post cibos)
p.m. afternoon/evening (L. post meridiem)

Purpose

To reduce the risk of medication errors, prescribers are encouraged to list the intended purpose of the medication (e.g., insomnia, high blood pressure, etc.). This is vital, as it helps pharmacists avoid errors from misreading the medication or dose. It is also important because it helps patients understand the purpose of each medication.

Overall, the information included in a prescription ensures that the patient receives the correct medication in the correct amount and that it is administered correctly with the correct frequency. This information is essential for ensuring that the medication is safe and effective for the patient. The use of abbreviations in medical prescriptions has led to medical errors and is widely discouraged. Care should be taken to ensure that abbreviations are properly interpreted.

Reviewers

  • Frances Aguilar, PharmD
  • Brian Sullivan, MD

Published: January 20, 2023