The sig pipeline — read it, translate it, calculate the day supply
Sig → Daily dose → Qty ÷ daily dose = day supply
Every prescription you enter follows this three-step path. Reading the sig correctly is Step 1 — everything downstream depends on it.
Frequency abbreviations
QD / QAM / QHS = once daily
BID = twice daily (every 12 hr)
TID = three times daily
QID = four times daily
Q4H = every 4 hr (6×/day)
Q6H = every 6 hr (4×/day)
Q8H = every 8 hr (3×/day)
PRN = as needed
BID = twice daily (every 12 hr)
TID = three times daily
QID = four times daily
Q4H = every 4 hr (6×/day)
Q6H = every 6 hr (4×/day)
Q8H = every 8 hr (3×/day)
PRN = as needed
Route & timing
PO = by mouth | SL = sublingual
SQ / SC = subcutaneous
IM = intramuscular
IV = intravenous
AU = both ears | AD = right ear
AS = left ear | OU = both eyes
AC = before meals | PC = after meals
gtt = drops (guttae)
SQ / SC = subcutaneous
IM = intramuscular
IV = intravenous
AU = both ears | AD = right ear
AS = left ear | OU = both eyes
AC = before meals | PC = after meals
gtt = drops (guttae)
Roman numerals in sigs
ss = ½ | i = 1 | ii = 2 | iii = 3
iv = 4 | v = 5 | vi = 6
vii = 7 | viii = 8 | x = 10
"Max viii tabs/day" = max 8 tablets/day
"i-ii tabs" = 1 to 2 tablets
Context: "iv" can be 4 OR intravenous
iv = 4 | v = 5 | vi = 6
vii = 7 | viii = 8 | x = 10
"Max viii tabs/day" = max 8 tablets/day
"i-ii tabs" = 1 to 2 tablets
Context: "iv" can be 4 OR intravenous
PRN day supply rule
Always use maximum allowed frequency for PRN medications in the day supply calculation.
CII controlled substances: use the stated max dosing (not what the patient actually takes).
"Q4-6H PRN" → use Q4H (6×/day)
"1-2 tabs" → use 2 tablets per dose
CII controlled substances: use the stated max dosing (not what the patient actually takes).
"Q4-6H PRN" → use Q4H (6×/day)
"1-2 tabs" → use 2 tablets per dose
★ PTCB tip: Sig interpretation questions appear in Order Entry & Processing. Common test formats: (1) translate a sig to plain English, (2) calculate day supply from a sig + quantity, (3) identify the maximum daily dose from a range sig, (4) flag an early refill by comparing day supply to days since fill. Know your frequency abbreviations cold — BID vs TID vs QID is tested every exam.
Most common sig errors in practice: (1) Entering BID as once daily — doubles refill frequency. (2) Not using max dosing for PRN CII — underestimates day supply, allows early fill. (3) Confusing "iv" (4 tablets) with "IV" (intravenous) — context is everything. (4) Missing the frequency divisor for complex tapers — 40 mg/day in 3 divided doses is NOT 40 mg per dose.
Six worked examples from simple sig translation through complex multi-phase day supply calculations.
EasyRetail
Rx: "ii gtt AU BID." Patient asks what this means.
Translate the sig to plain English.
Break each abbreviation:ii = 2 | gtt = drops | AU = both ears | BID = twice daily
Plain English:Instill 2 drops in both ears twice daily.
✓ Counsel patient: 2 drops, both ears, morning and night
EasyRetail
Metformin 500 mg. Sig: "1 tab PO BID." Quantity: 60 tablets.
Calculate the day supply.
Step 1 — daily dose from sig:1 tab × 2 (BID) = 2 tabs/day
Step 2 — day supply:60 ÷ 2 = 30 days
✓ Enter 30 days in the system
MediumRetail
Oxycodone 5 mg. Sig: "1-2 tabs PO Q4-6H PRN pain." Qty: 60 tabs. Schedule II.
What day supply should be entered? (CII = maximum dosing)
Max dose per administration:2 tablets
Max frequency:Q4H = every 4 hours = 6 times per day
Max daily dose:2 × 6 = 12 tablets/day
Day supply:60 ÷ 12 = 5 days
✓ Enter 5 days — CII always uses maximum dosing
MediumRetail
Albuterol HFA. Sig: "ii puffs Q4-6H PRN SOB." Canister: 200 puffs.
Day supply at maximum PRN frequency (Q4H)?
Max puffs per day:2 puffs × 6 (Q4H) = 12 puffs/day
Day supply:200 ÷ 12 = 16.67 → 16 days (round down)
✓ 16-day supply — always round DOWN for day supply
HardRetail
Medrol Dosepak: "6 tabs Day 1, 5 Day 2, 4 Day 3, 3 Day 4, 2 Day 5, 1 Day 6."
Total tablets needed and day supply?
Add each day:6 + 5 + 4 + 3 + 2 + 1 = 21 tablets
Days in course:6 days
✓ Dispense 21 tablets, enter 6-day supply — memorize this one
HardPatient scenario
TB treatment: rifampin 300 mg, "2 tabs QD × 60 days, then 1 tab QD × 120 days."
Total 300 mg tablets for the complete 6-month course?
Phase 1 (2 months = 60 days):2 tabs × 60 = 120 tablets
Phase 2 (4 months = 120 days):1 tab × 120 = 120 tablets
Total:120 + 120 = 240 tablets
✓ 240 tablets total for the complete TB course
TB treatment requires a full course — incomplete treatment causes drug-resistant TB. Dispensing the correct quantity for 6 full months is critical.
How this quiz works: Pick your question count and difficulty, then start. After answering, click Reveal explanation to see the full step-by-step solution — answers never show automatically. Score and type breakdown appear at the end.
ⓘ This lesson has 32 questions in the bank. A 10-question quiz draws a random subset. Run multiple sets to cycle through all questions.
ⓘ This lesson has 32 questions in the bank. A 10-question quiz draws a random subset. Run multiple sets to cycle through all questions.
How many questions?
Question difficulty
Options
Randomize question order
Shuffle every time you start
Timed mode
45-second countdown per question
Number of sets
Each set draws a fresh pool
1
Question 1 of 10
--%
Score
Quiz complete!
Lesson 6 · Sig Interpretation · AlabamaPharmTech.com
--
Correct
--
Wrong
--
Skipped
--
Time
Answer review — every question this session