Medication Abbreviations: Meanings and Latin Roots
Medication orders compress a drug, a dose, a route, and a schedule into a few characters, such as ondansetron 4 mg IV q6h PRN nausea. Most of that shorthand is Latin: q is quaque, every, and PRN is pro re nata, as needed. The tables below decode the abbreviations you will meet in orders, prescriptions, and notes, give the Latin behind each one, and mark the ones patient-safety groups say to stop using.
On this page: reading an order · frequency and timing · routes · doses, units, and forms · drips and infusions · prescriptions and sig codes · other medication shorthand · abbreviations to stop using
How to read a medication order
Orders follow a fixed sequence: drug, dose, route, frequency, and, for as-needed drugs, the reason. Prescriptions add the quantity to dispense and the number of refills.
| As written | Read as |
|---|---|
| metoprolol tartrate 25 mg PO BID | metoprolol tartrate, 25 milligrams, by mouth, twice a day |
| ondansetron 4 mg IV q6h PRN nausea | 4 milligrams intravenously, every 6 hours as needed for nausea |
| enoxaparin 40 mg SUBQ daily | 40 milligrams under the skin, once a day |
| insulin glargine 20 units SUBQ QHS | 20 units under the skin, every night at bedtime |
| acetaminophen 650 mg PO q6h PRN pain, max 3 g/day | 650 milligrams by mouth every 6 hours as needed for pain, no more than 3 grams a day |
| norepinephrine gtt 0.05 mcg/kg/min, titrate to MAP > 65 | a continuous infusion at 0.05 micrograms per kilogram per minute, adjusted to keep the mean arterial pressure above 65 |
| Sig: 1 tab PO BID x 10 days, Disp #20, RF 0 | label: take 1 tablet by mouth twice a day for 10 days; dispense 20 tablets; no refills |
Examples on this page show how orders are written. They are not dosing advice.
Frequency and timing
Most schedule abbreviations are built from a few Latin words: quaque (every), hora (hour), die (day), and in die (in a day). Charts write them in capitals or lowercase, with or without periods: BID, bid, and b.i.d. mean the same thing.
| Abbreviation | Latin | Meaning |
|---|---|---|
| qd | quaque die, every day | once a day. Do-not-use list: write daily. |
| BID | bis in die, twice in a day | two times a day, usually morning and evening |
| TID | ter in die, three times in a day | three times a day |
| QID | quater in die, four times in a day | four times a day, usually spread across waking hours |
| qod | quaque altera die, every other day | every second day. Do-not-use list: write every other day. |
| qh, q4h, q6h, q8h, q12h | quaque hora, every hour | every hour, or every 4, 6, 8, or 12 hours, around the clock |
| q4-6h | every 4 to 6 hours, a range usually paired with PRN | |
| qAM, qPM | quaque die ante meridiem, post meridiem | every morning, every evening |
| QHS, qhs | quaque hora somni, every hour of sleep | every night at bedtime. ISMP accepts QHS or qhs; error-prone: the handwritten mixed form Qhs, misread as qhr, every hour. |
| HS | hora somni, the hour of sleep | at bedtime. Error-prone in lowercase: hs has also meant half-strength, so ISMP says write half-strength in words and use HS, in capitals, only for bedtime. |
| AC | ante cibum, before food | before meals |
| PC | post cibum, after food | after meals |
| ACHS | ante cibum et hora somni | before meals and at bedtime, the usual schedule for fingerstick glucose checks |
| PRN | pro re nata, for the occasion that has arisen | as needed: given only when the stated reason applies, no more often than the interval allows |
| stat | statim, immediately | now, as fast as possible |
| ad lib | ad libitum, at one's pleasure | freely, as much as wanted; common in diet and activity orders |
| ATC | around the clock: scheduled doses day and night, the opposite of PRN | |
| x1, x 7 days | one dose; for 7 days. Spelling out for 7 days removes any doubt between days and doses. | |
| TIW, BIW | three times a week, twice a week. Error-prone: misread as three or two times a day; write 3 times weekly. |
QID and q6h both mean four doses a day, but they are not the same order. QID usually spreads the doses across waking hours, often with meals and at bedtime; q6h means every 6 hours around the clock, so one dose falls overnight. The same goes for BID versus q12h and TID versus q8h.
Routes
| Abbreviation | Latin | Meaning |
|---|---|---|
| PO | per os, by the mouth | by mouth |
| NPO | nil per os, nothing by the mouth | nothing by mouth, for example before surgery |
| SL | sub lingua, under the tongue | dissolved under the tongue |
| PR | per rectum | rectally |
| PV | per vaginam | vaginally |
| IV, IVP, IVPB | intravenous; IV push, injected directly over a short time; IV piggyback, a small bag run into the main line | |
| IM | intramuscular, into a muscle | |
| SUBQ, subQ, SC, SQ | subcutaneous, under the skin. Error-prone: SC has been misread as SL, SQ as 5 every, and the q in sub q as every; ISMP recommends SUBQ, in capitals with no spaces or periods, or subcutaneously. | |
| ID | intradermal, into the skin, as with a tuberculin skin test | |
| IN | intranasal. Error-prone: misread as IM or IV; write intranasal. | |
| IT | intrathecal, into the spinal fluid. Error-prone: misread as intratracheal, intratumor, intratympanic, or inhalation therapy; write intrathecal. | |
| inh, neb, MDI | nebula, mist | inhaled; nebulized; metered-dose inhaler |
| top, TD | topical, on the skin; transdermal, absorbed through the skin, usually from a patch | |
| per NG, per GT | through a nasogastric or gastrostomy tube | |
| OD, OS, OU | oculus dexter, sinister, uterque | right eye, left eye, each eye. Error-prone: confused with the ear abbreviations, and OD with once daily; write the words. |
| AD, AS, AU | auris dextra, sinistra, utraque | right ear, left ear, each ear. Error-prone: confused with the eye abbreviations; write the words. |
British prescriptions add one more trap: there, od usually means once daily, from omni die, every day, not the right eye.
Doses, units, and forms
| Abbreviation | Meaning |
|---|---|
| mg, mcg, g, kg | milligram, microgram (one thousandth of a milligram), gram, kilogram. Write mcg: the symbol µg has been misread as mg, a thousandfold error. |
| mL, L | milliliter, liter. Write mL: cc, for cubic centimeter, has been misread as u for units. |
| mEq, mmol | milliequivalent, millimole; used for electrolytes such as potassium chloride and phosphate |
| units | always spelled out: U and u are on the do-not-use list because they have been misread as 0, 4, or cc |
| international units | spelled out too: IU is on the do-not-use list because it has been misread as IV or 10 |
| mg/kg, mg/m2 | per kilogram of body weight; per square meter of body surface area (BSA), common in chemotherapy and pediatrics |
| gtt | guttae, drops: 1 gtt is one drop. In hospital notes it usually means a drip; see below. |
| tsp, tbsp | teaspoon, tablespoon. Prescriptions give liquid doses in mL, because kitchen spoons vary. |
Dose forms
| Abbreviation | Latin | Meaning |
|---|---|---|
| tab, cap | tabella, capsula | tablet, capsule |
| supp | suppositorium | suppository |
| syr, elix | syrupus, elixir | syrup; elixir, a sweetened liquid that contains alcohol |
| susp, soln | suspension, which needs shaking; solution | |
| ung, crm | unguentum | ointment; cream |
| inj | injectio | injection |
| IR, ER, XR, XL, SR, CR, LA | immediate release; extended, sustained, or controlled release; long acting. Extended-release forms usually should not be crushed or chewed. | |
| DR, EC | delayed release; enteric coated, built to pass the stomach before dissolving | |
| ODT | orally disintegrating tablet, which dissolves on the tongue |
Two rules apply to every written dose. Never add a trailing zero: write 5 mg, because 5.0 mg can be read as 50 mg. Always add a leading zero: write 0.5 mg, because .5 mg can be read as 5 mg. The Joint Commission allows a trailing zero only where it shows real precision, such as a lab result, a lesion size, or a catheter size, and never in a medication order.
Drips and infusions
In hospital notes, gtt usually means a continuous IV infusion rather than drops: heparin gtt, insulin gtt. Drip orders give a rate, often weight based, and many add a goal to titrate toward.
| Abbreviation | Meaning | As written |
|---|---|---|
| mL/hr | milliliters per hour, the pump rate | LR at 125 mL/hr |
| mcg/kg/min | micrograms per kilogram of body weight per minute | propofol 20 mcg/kg/min |
| mcg/min | micrograms per minute, not weight based | norepinephrine 8 mcg/min |
| mg/hr | milligrams per hour | nicardipine 5 mg/hr |
| units/hr, units/kg/hr | units per hour, or per kilogram per hour | insulin gtt 0.1 units/kg/hr |
| bolus | a one-time dose given quickly, often before a drip starts | heparin 80 units/kg IV bolus, then 18 units/kg/hr |
| titrate, MAP | adjust the rate toward a goal; mean arterial pressure, the usual goal for vasopressors | titrate to MAP > 65 |
| wean | lower the rate step by step | wean levo as tolerated |
| KVO, TKO | keep vein open, to keep open: a slow rate that keeps the IV line from clotting | NS at KVO |
| PCA | patient-controlled analgesia: a pump that lets the patient give small doses within set limits (demand dose, lockout interval, and sometimes a basal rate) | hydromorphone PCA |
| NS, 1/2NS, LR, D5W | normal saline (0.9% sodium chloride), half-normal saline (0.45%), lactated Ringer's, 5% dextrose in water | D5 1/2NS + 20 mEq KCl at 100 mL/hr |
| TPN, PPN | total parenteral nutrition, usually through a central line; peripheral parenteral nutrition | TPN per nutrition team |
| VTBI | volume to be infused, an infusion pump setting | VTBI 1,000 mL |
ICU notes also shorten drip names: levo (norepinephrine, from the brand Levophed), vaso (vasopressin), neo (phenylephrine, from Neo-Synephrine), epi (epinephrine), and precedex (dexmedetomidine). The nicknames are common in notes and handoffs, but ISMP advises against abbreviating drug names in orders at all.
Prescriptions and sig codes
Outpatient prescriptions keep the oldest Latin. The directions line is still called the sig, from signa, mark or write, because it is what goes on the label.
| Abbreviation | Latin | Meaning |
|---|---|---|
| Rx | recipe, take | prescription; the symbol began as the instruction take |
| Sig | signa, mark | directions for the label |
| Disp, # | dispense; the quantity to dispense, as in #30 | |
| RF, NR | refills; no refills | |
| DAW | dispense as written: no generic substitution | |
| qs | quantum sufficit, as much as suffices | a sufficient quantity, as in qs ad 100 mL: add enough to make 100 mL |
| ut dict, UD | ut dictum, as directed | as directed. Error-prone: UD has been misread as unit dose; write as directed. |
| aa | ana, of each | equal amounts of each ingredient, in compounding |
| c̄, s̄ | cum, with; sine, without | with, without, written with a bar over the letter; typed notes use w/ and w/o |
| ā, p̄ | ante, before; post, after | before, after, also written with a bar |
| ss | semis, half | one half. Error-prone: misread as 55, and also used for sliding scale; write one-half. |
| i, ii, iii | Roman numerals | one, two, three, as in tab ii, two tablets, on older prescriptions |
| OTC | over the counter, sold without a prescription |
Other medication shorthand in notes
| Abbreviation | Meaning |
|---|---|
| MAR | medication administration record, where each dose given is documented |
| med rec | medication reconciliation: matching home medications against the admission or discharge list |
| NKDA | no known drug allergies |
| ADR | adverse drug reaction |
| hold for SBP < 100, HR < 60 | hold parameters: skip the dose if systolic blood pressure is below 100 or heart rate is below 60 |
| NTE, max | not to exceed; maximum dose, as in NTE 3 g/day |
| SSI | sliding scale insulin, doses matched to the glucose reading. Error-prone: SSI has been misread as strong solution of iodine, and SSRI, used for sliding scale regular insulin, as the antidepressant class; write sliding scale insulin. |
| U-100 | insulin concentration, 100 units per mL, printed on the label; not the banned U for units in a dose |
| D/C | discontinue, or discharge. Error-prone: the two meanings get confused; write the word. |
Abbreviations to stop using
Two lists matter. The Joint Commission's official do-not-use list is required for accredited hospitals and covers every order and all medication-related documentation that is handwritten, typed as free text, or printed on order forms. ISMP's list of error-prone abbreviations, symbols, and dose designations is longer and voluntary, but many hospitals adopt parts of it. The stakes are real: in one review of medication errors reported to the MEDMARX program from 2004 to 2006, about 4.7 percent involved an abbreviation, and QD alone accounted for roughly 43 percent of the ones that could be classified.
The Joint Commission's do-not-use list
| Instead of | Write | Why |
|---|---|---|
| U, u | units | read as 0, 4, or cc |
| IU | international units | read as IV or 10 |
| QD, qd | daily | read as QID, or confused with QOD |
| QOD, qod | every other day | read as QD or QID |
| 5.0 mg | 5 mg | a missed decimal point gives 50 mg |
| .5 mg | 0.5 mg | a missed decimal point gives 5 mg |
| MS, MSO4, MgSO4 | morphine sulfate, magnesium sulfate | the two drugs get confused |
ISMP's error-prone list
| Instead of | Write | Why |
|---|---|---|
| µg | mcg | read as mg |
| cc | mL | read as u, units |
| SC, SQ, sub q | SUBQ or subcutaneously | read as SL, as 5 every, or the q as every |
| hs, or HS for half-strength | half-strength in words; HS only for bedtime | one abbreviation, two meanings |
| Qhs, qn | QHS or qhs for bedtime | read as qhr or qh, every hour |
| q6PM | 6 PM daily | read as every 6 hours |
| TIW, BIW | 3 times weekly, 2 times weekly | read as three or two times a day |
| D/C | discharge, discontinue | discharge medications stopped by mistake |
| UD | as directed | read as unit dose |
| IN, IJ | intranasal, injection | read as IM or IV; IJ also as intrajugular |
| IT | intrathecal | read as intratracheal, intratumor, intratympanic, or inhalation therapy |
| AD, AS, AU, OD, OS, OU | right ear, left eye, and so on | ears and eyes confused; OD also read as once daily |
| SSI, SSRI, ss | sliding scale insulin, one-half | SSI read as strong solution of iodine; SSRI (sliding scale regular insulin) read as the antidepressant class; ss read as 55 |
| @, &, + | at, and | @ and & read as 2, + read as 4 |
| / | per | a slash between doses read as the number 1 |
| q2° | every 2 hours | the degree sign for hour read as a zero: q 20 |
| drug name abbreviations | the full drug name | short forms get mistaken for other drugs |
ISMP's list also includes > and <, which have been read as the opposite of what was meant, and < as the number 4; write more than and less than in orders. ISMP notes that banning every abbreviation is unrealistic, so where an uncommon or ambiguous one is used, the writer should define it. The trainer's dosing strings mirror real charts, and many of the older ones still show qd: read those as practice for older charts and type daily in your own orders.
Practice typing them
Dosing strings are some of the slowest text in a note: digits, units, slashes, and capitals packed into a few characters. The trainer appends realistic doses to drug names, so you can drill exactly this shorthand at speed.
Drug names with dosing strings ICU drips and titrations Nursing medication charting
Preset links open the trainer with those settings already applied; you can change them afterward.
For abbreviations grouped by note section, from the HPI to the plan, see common medical abbreviations in clinical notes. For how orders fit into the structure of a note, see clinical documentation typing. For insulin types and the DKA and HHS consensus, see insulin types, diabetes medications, and DKA.
Common questions
What does PRN mean?
PRN stands for pro re nata, Latin for roughly "for the occasion that has arisen." It means as needed: the dose is given only when the reason in the order applies, and no more often than the interval allows, as in ondansetron 4 mg IV q6h PRN nausea.
What is the difference between QID and q6h?
Both mean four doses a day. QID (quater in die) usually spreads them across waking hours, often with meals and at bedtime. q6h means every 6 hours around the clock, so one dose falls overnight. The same distinction applies to BID versus q12h and TID versus q8h.
What do QHS and HS mean?
Both mean at bedtime, from hora somni, the hour of sleep; QHS adds quaque, every, so every night at bedtime. ISMP's 2024 list accepts QHS or qhs and HS in capitals for bedtime, but flags lowercase hs, which has also meant half-strength, and the handwritten forms Qhs and qn, which have been misread as every hour.
Why is QD on the do-not-use list?
Written quickly, QD has been misread as QID (four times a day) and confused with QOD (every other day). The Joint Commission requires writing daily instead. In one review of medication errors linked to abbreviations, QD accounted for roughly 43 percent of the ones that could be classified.
What does gtt mean?
gtt comes from guttae, Latin for drops. On eye and ear prescriptions it still means drops. In hospital notes, heparin gtt or insulin gtt means a continuous IV infusion, a drip.
Sources
- ISMP List of Error-Prone Abbreviations, Symbols, and Dose Designations (2024), which also marks the Joint Commission's required items.
- The Joint Commission's "Do Not Use" List: Brief Review, in Making Health Care Safer II (AHRQ), the source of the MEDMARX figures above.