What does sig mean on a prescription?
It's short for the Latin signa, meaning "write" or "label." The sig is the directions portion of the prescription — the part that becomes the label the patient reads.
Order Entry
Sig Codes Cheat Sheet: The Pharmacy Abbreviations the PTCB Tests
By the RxReflex Content Team · Last reviewed August 6, 2026
A sig code is the shorthand a prescriber uses to write directions. "Sig" comes from the Latin signa ("write" or "label"). Sig codes fall into three groups: frequency (how often), route (how it goes in), and dosage form (what it is). On the PTCE they show up inside Order Entry & Processing questions, which is 22.5% of the 2026 exam.
What is a sig code, and where does it sit on the prescription?
The sig is the directions line — the part that becomes the patient-facing label. On a prescription for amoxicillin 500 mg, 1 cap PO TID x 10 days, the sig is 1 cap PO TID: take one capsule by mouth three times a day.
Your job in order entry is to turn that shorthand into a sentence a patient can follow without calling the pharmacy. Get it wrong and the label is wrong, which is why this is tested as a safety topic and not a vocabulary quiz.
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How it's actually tested
The exam rarely asks "what does TID mean?" in isolation. It gives you a full sig and asks what the label should say, or which part of the sig is the problem. Learn the codes, then practice translating whole strings.
Frequency abbreviations — how often
| Sig code | Meaning |
|---|---|
| QD | Once a day (see the do-not-use list below) |
| BID | Twice a day |
| TID | Three times a day |
| QID | Four times a day |
| q4h / q6h / q8h / q12h | Every 4 / 6 / 8 / 12 hours |
| HS | At bedtime (do-not-use) |
| AC | Before meals |
| PC | After meals |
| PRN | As needed |
| STAT | Immediately / now |
The distinction candidates lose points on is QID versus q6h. Four times a day means four doses during waking hours; every six hours means around the clock, including overnight. They are not interchangeable, and a drug with a narrow therapeutic window cares about the difference.
Route abbreviations — how it goes in
| Sig code | Meaning |
|---|---|
| PO | By mouth |
| SL | Under the tongue (sublingual) |
| PR | Rectally |
| IM | Intramuscular |
| IV | Intravenous |
| SubQ | Under the skin (subcutaneous) |
| TOP | Topical (on the skin) |
| INH | Inhaled |
| OD / OS / OU | Right eye / left eye / both eyes |
| AD / AS / AU | Right ear / left ear / both ears |
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The one to over-learn
The eye/ear pairs are the classic trap. O = oculus (eye), A = auris (ear); D = dexter (right), S = sinister (left), U = uterque (both). Ear drops in an eye is a real dispensing error, and the exam knows it. If the Latin doesn't stick, remember that the eye codes come first alphabetically — A before O is ear before eye is backwards, so hold onto the Latin.
Dosage form abbreviations — what it is
| Sig code | Form | Sig code | Form |
|---|---|---|---|
| TAB | Tablet | CAP | Capsule |
| SYP | Syrup | SUSP | Suspension |
| SOL | Solution | SUPP | Suppository |
| OINT | Ointment | CRM | Cream |
| GTT | Drops | INJ | Injection |
| LOZ | Lozenge |
SUSP versus SOL matters more than it looks. A suspension has undissolved particles, so it needs a shake well auxiliary label; a solution does not. That auxiliary-label decision is a fair exam question.
The ten abbreviations you must READ but never WRITE
This is the part most sig-code lists leave out, and it is where the exam actually separates candidates. Some of the abbreviations above are on The Joint Commission's official "Do Not Use" list, built from ISMP's error-prone abbreviations. You still have to recognize them, because prescribers still write them — but you must never produce them yourself on a label, an order, or a transcription.
| Never write | Write instead | Why |
|---|---|---|
| U or u | unit | The U reads as 0, 4, or cc |
| IU | unit | Reads as IV or the number 10 |
| QD / Q.D. | daily | Reads as QID |
| QOD / Q.O.D. | every other day | Reads as QD or QID |
| 1.0 mg (trailing zero) | 1 mg | A missed decimal is a 10× overdose |
| .5 mg (no leading zero) | 0.5 mg | A missed decimal is a 10× overdose |
| MS / MSO4 / MgSO4 | morphine sulfate / magnesium sulfate | Two different drugs, one abbreviation |
| µg | mcg | Reads as mg — a 1,000× error |
| cc | mL | Reads as U |
| HS | at bedtime | Reads as half-strength |
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The trap
Notice that QD and HS appear in both tables on this page. That is not a contradiction — it is the whole point. You need to translate them when you see them, and you need to never write them. An exam question that shows you a handwritten "QD" is usually asking about the second half.
Worked translations
Read each sig left to right: how much → what form → what route → how often → how long.
| The sig | The label should read |
|---|---|
| 1 tab PO BID PC | Take 1 tablet by mouth twice a day after meals |
| 2 gtt OU QID x 7d | Instill 2 drops into both eyes four times a day for 7 days |
| 1 cap PO q8h PRN pain | Take 1 capsule by mouth every 8 hours as needed for pain |
| 5 mL PO TID AC | Take 5 mL by mouth three times a day before meals |
| 1 supp PR HS PRN | Insert 1 suppository rectally at bedtime as needed |
Two habits that prevent most order-entry errors: read the route before the frequency (route errors are the dangerous ones), and say the finished label out loud. If it doesn't sound like something you'd tell a patient, it's wrong.
How to actually memorize them
- arrow_rightGroup them, don't list them. Frequency, route, form — three small sets beat one long alphabet.
- arrow_rightLearn the Latin roots for the pairs only. OD/OS/OU and AD/AS/AU are the ones where the root does real work. For the rest, rote is faster.
- arrow_rightPractice whole sigs, not single codes. Recognizing TID in isolation is not the skill being tested; producing a correct label from a full string is.
- arrow_rightDrill the do-not-use list separately. It is a Patient Safety topic wearing an Order Entry costume, and it carries its own questions.
- arrow_rightKeep a sheet on your phone. Sig codes reward short, frequent exposure far more than one long session.
Sig codes — FAQ
How many sig codes do I need to know for the PTCB exam?
Roughly 30 covers the high-yield set: about 10 frequency codes, 10 route codes, and 10 dosage forms. Add the ten error-prone abbreviations on the Joint Commission Do Not Use list and you've covered what the exam realistically asks.
What is the difference between QID and q6h?
QID is four times during waking hours. q6h is every six hours around the clock, including overnight. They produce four doses a day either way, but the spacing differs — and for some drugs that matters clinically.
Why is QD on the do-not-use list if it's still taught?
Because you have to read it and must not write it. Handwritten QD is easily misread as QID, which quadruples the dose. You translate it when a prescriber writes it, then document "daily" yourself.
What do OD, OS, and OU mean?
Right eye, left eye, and both eyes. The ear equivalents are AD, AS, and AU. Mixing up the eye and ear sets is a genuine dispensing error and a recurring exam question.
Are sig codes on the 2026 PTCE?
Yes. They live in Order Entry & Processing, which is 22.5% of the 2026 content outline. The exam is entirely multiple-choice — 90 questions, 80 scored, in 110 minutes.
Drill sig codes until they're automatic
The Sig Codes & Abbreviations cheat sheet is one of the free sheets in RxReflex — swipe it, zoom it, save it to your photos. Then practice the translations against real order-entry questions. Free to start on iOS and Android.
Keep studying
Pharmacy Math Cheat SheetEvery conversion + formula, and the 5 question types every PTCE math problem falls into.
LASA Drugs Cheat SheetThe look-alike/sound-alike pairs the exam loves — and how Tall Man letters keep them straight.
How to Read a PrescriptionThe anatomy of an Rx, all ten DAW codes, and how to read an NDC off a stock bottle.Prefer a printable version? Grab “The PTCB Pass Code” free PDF — the highest-yield facts, formulas & traps on 22 pages.
Last reviewed August 6, 2026 by the RxReflex Content Team. Educational use only — not medical advice. Exam policies and fees are set by PTCB — always confirm details at ptcb.org. Verify clinical specifics with your pharmacist or a current label source such as DailyMed. RxReflex is not affiliated with or endorsed by the Pharmacy Technician Certification Board (PTCB).