When I trained new hires at the pharmacy counter, sig codes were one of the quickest ways to make capable, calm people feel behind. The prescription label looked like a tiny secret language. The good news is that it is not infinite. Most pharmacies run on a pretty small set of repeating patterns, and once you learn to translate those patterns into plain English, your speed jumps fast.
This guide will help you decode common prescription shorthand, avoid the classic “looks right” mistakes, and build a study routine that sticks for the Pharmacy Tech exam and real workflow.
First, what “sig” really means
Sig. comes from the Latin signa, commonly taught as “write” or “write on the label.” In pharmacy land, it is simply the directions for use that appear on the label.
The sig is usually built from a few categories:
- Route: by mouth, in the eye, on the skin
- Dose: how much each time (tablet count, mL, drops)
- Frequency: how often (daily, twice daily, every 6 hours)
- Timing: with food, at bedtime, in the morning
- Indication: for pain, for nausea, for cough
- Duration or limits: for 10 days, maximum per day
When you see a string of abbreviations, your job is to drop each piece into the right bucket, then read it out like a normal sentence.
A quick decoding method that works under pressure
Here is the method I taught at pickup when we had a line and the phone ringing.
Step 1: Circle the route
Route terms are the “anchor.” Once you know where the medication is going, the rest is less chaotic. Examples: PO, PR, SL, IM, SQ, IV, ophth, otic, top, inh, nas.
Step 2: Find the dose form and quantity
Look for the “unit words” and numbers: tab, cap, mL, tsp, g, puff, spray, gtt.
Step 3: Translate the frequency into a number
Convert shorthand into something you can picture on a clock: daily, twice daily, every 6 hours, before meals.
Step 4: Add timing and limits last
Finish with “with food,” “as needed,” and any maximum daily dose.
Step 5: Say it out loud in plain English
If you cannot say it smoothly, you probably have a mismatch (like a route that does not fit the dosage form).
Example: “1 tab PO bid PRN pain” becomes: “Take 1 tablet by mouth twice daily as needed for pain.”
Case tip: You will see these in lowercase, uppercase, or mixed on labels and e-prescriptions. The meaning does not change, but for studying I keep them mostly lowercase and treat case as “cosmetic.”
Common sig codes (and how to remember them)
Below are high-frequency sig codes you will see on labels and in test questions. I am giving plain-English meanings plus a memory hook when one helps.
Routes
- PO = by mouth (think “per os”)
- SL = under the tongue (sublingual)
- PR = rectally
- PV = vaginally
- IM = into the muscle (intramuscular)
- SQ / SubQ = under the skin (subcutaneous)
- IV = into the vein (intravenous)
- top = apply to the skin (topical)
- inh = inhale
- ophth = in the eye (ophthalmic)
- otic = in the ear
- nas = in the nose (nasal)
Frequency and timing
- qd = once daily
- qday = once daily (a clearer way some systems write it)
- bid = twice daily
- tid = three times daily
- qid = four times daily
- qod = every other day
- q4h, q6h, q8h, q12h = every 4, 6, 8, or 12 hours
- qam = each morning
- qpm = each evening
- qhs = each night at bedtime
- ac = before meals
- pc = after meals
- hs = at bedtime
- stat = immediately
- qwk = every week
- biw = twice weekly
- tiw = three times weekly
Directions and special instruction words
- prn = as needed
- ud = as directed (usage varies by site; you may also see it used differently in other settings)
- uad = use as directed (very common in outpatient labels)
- c̄ = with (c with a bar, traditional shorthand)
- s̄ = without (s with a bar, traditional shorthand)
- taper = gradually decrease dose on a schedule
- x = for (example: x 10 days)
Dosage forms and units
- tab = tablet
- cap = capsule
- supp = suppository
- gtt = drop(s)
- tsp = teaspoon (5 mL)
- tbsp = tablespoon (15 mL)
- mL = milliliter
- g = gram
- mg = milligram
- mcg = microgram
- IU = international units
- ung = ointment
- crm = cream
- soln = solution
- susp = suspension
A note I give every student: Some abbreviations (especially “qd” and “qod”) are discouraged in certain settings due to look-alike risks. Your exam may still test them because they are common in the wild. Learn them, and learn why they can be risky. On the job, follow your pharmacy’s policy and any “do not use” list your organization uses.
Medical abbreviations you will see around sigs
Not every abbreviation is a sig code. Many are clinical shorthand that appear in indications, patient profiles, prescriber notes, or counseling prompts.
Common clinical abbreviations
- BP = blood pressure
- HR = heart rate
- RR = respiratory rate
- Temp = temperature
- Dx = diagnosis
- Hx = history
- Rx = prescription or therapy (context matters)
- Tx = treatment
- Sx = symptoms
- PRN = as needed (shows up clinically too)
- NKA = no known allergies
- NPO = nothing by mouth
- SOB = shortness of breath
- URI = upper respiratory infection
- UTI = urinary tract infection
Common lab abbreviations (you do not need to be a nurse to recognize these)
- A1C = average blood glucose over about 2 to 3 months (diabetes marker)
- INR = blood clotting measure used with warfarin monitoring
- Cr / SCr = creatinine (a lab value used to estimate kidney function)
- eGFR = estimated kidney filtration rate
- LFTs = liver function tests
As a tech, your role is not to diagnose. But recognizing these abbreviations helps you spot when a prescription direction, medication, or dose looks mismatched for the patient profile and when to escalate questions to the pharmacist.
The danger pairs that trick smart students
Most mistakes happen because two abbreviations look similar or feel interchangeable. Here are the ones I watched new staff stumble over most often.
- qhs vs hs: both relate to bedtime. Many people use them loosely, but you should know qhs means each night at bedtime.
- ac vs pc: before meals vs after meals. Think: A = ahead of meals, P = post meals.
- tid vs qid: three times daily vs four times daily. If you mix these up, the whole day schedule changes.
- OS, OD, OU: left eye, right eye, both eyes. Also note OD can mean “once daily” in other contexts, which is why eye abbreviations matter.
- AD, AS, AU: right ear, left ear, both ears (same pattern as eyes, different letters).
- otic vs ophth: ear vs eye. Similar-looking words, very different place.
- mg vs mcg: milligram vs microgram. This is not a small mistake.
- tsp vs tbsp: 5 mL vs 15 mL. A tablespoon is three teaspoons.
If you do nothing else, build flashcards around these danger pairs. They deliver an outsized return because they prevent high-impact errors.
A fast study plan (15 minutes a day)
You can learn a lot of sig code quickly if you study in the same way you will use it: recognizing patterns under time pressure.
Days 1 to 3: Learn the core 30
Focus on the most common routes and frequencies first (PO, bid, tid, qid, q4h, q6h, q8h, q12h, qd, qam, qhs, ac, pc, prn, gtt, ophth, otic, top, inh, nas, mL, tsp, tbsp, tab, cap).
Days 4 to 7: Translate 20 full sigs per day
Do not just memorize “bid = twice daily.” Practice turning full strings into plain English. Keep a notebook page split into two columns: sig and translation. Speed comes from repeated translation, not from staring at a list.
Week 2: Add the tricky ones and the clinical abbreviations
Add the danger pairs, eye and ear abbreviations, and common clinical shorthand (NPO, NKA, SOB, UTI, INR). Mix them into your translations so you learn in context.
Weekly maintenance: Rotate, do not cram
A quick rotation beats a weekend cram. Five minutes of review on three different days usually sticks better than one 30-minute session.
If you are building a broader exam plan, I mapped out a bigger structure in our Pharmacy Tech Exam guide, and for organizing your materials so you are not hunting through notes, see how to organise pharmacy tech exam study sources.
Practice: translate these sigs
Cover the answers first, then check yourself. This is the exact kind of practice I used to do with trainees between customers.
- Sig: 1 tab PO qd
- Sig: 2 caps PO bid
- Sig: 1 tab PO q6h prn pain
- Sig: Instill 1 gtt OU qhs
- Sig: Apply top bid
- Sig: Inhale 2 puffs q4h prn SOB
- Sig: Take 10 mL PO tid pc
- Sig: Insert 1 supp PV qhs x 7 days
Answers
- Take 1 tablet by mouth once daily.
- Take 2 capsules by mouth twice daily.
- Take 1 tablet by mouth every 6 hours as needed for pain.
- Instill 1 drop in both eyes at bedtime.
- Apply to the skin twice daily.
- Inhale 2 puffs every 4 hours as needed for shortness of breath.
- Take 10 mL by mouth three times daily after meals.
- Insert 1 suppository vaginally at bedtime for 7 days.
When to slow down and ask the pharmacist
In real pharmacy workflow, “quick” is great, but “quick and correct” is the whole job. Slow down and escalate when you see:
- Conflicting directions (example: “q6h” plus “once daily” in the same sig)
- A route that does not match the dosage form (example: “ophth” with something clearly meant for skin)
- Unusually high frequency without a clear maximum daily dose
- Look-alike abbreviations where one choice changes the meaning significantly (tid vs qid, mg vs mcg)
- Anything unclear, including handwriting, missing units, or abbreviations your pharmacy does not allow
On the exam, you are usually being tested on what the abbreviation means. On the job, you are also being tested on whether you notice when something does not add up.
FAQ
Are sig codes Latin?
Many come from Latin (PO, bid, tid, qid), but modern sigs are a mix of Latin-based abbreviations, English shorthand, and pharmacy conventions.
Is it okay to memorize a giant list?
A list helps you start, but speed comes from translation practice. Learn a core set, then drill full sigs daily.
What is the fastest way to stop mixing up ac and pc?
Practice them as opposites: write ten sample sigs with ac and rewrite the same sig with pc. The contrast makes the meaning stick.
Where can I get more structured study help?
Start with our Study Guides section if you want a broader framework beyond abbreviations.
