Ptcb Quiz: Days Supply Calculation
20 questions · exam conditions
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Days Supply CalculationQuestion 1 of 20

A prescription is written for Amoxicillin 400 mg/5 mL suspension with the following directions:

Sig: Take 1 tsp po bid x 10d

Dispense: QS

What is the total quantity, in mL, that should be dispensed to the patient?

50 mL
75 mL
100 mL
150 mL
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Ptcb Quiz

Ptcb Quiz: Days Supply Calculation

Practice Days Supply Calculation in Ptcb with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Days Supply Calculation, giving you a quick way to practice the rules, question types, and explanations that matter most for Ptcb.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

A prescription is written for Amoxicillin 400 mg/5 mL suspension with the following directions:

Sig: Take 1 tsp po bid x 10d

Dispense: QS

What is the total quantity, in mL, that should be dispensed to the patient?

  1. 50 mL
  2. 75 mL
  3. 100 mL (correct answer)
  4. 150 mL
Explanation: The correct answer is 100 mL.
  1. Convert the dose from teaspoons (tsp) to milliliters (mL): 1 tsp = 5 mL.
  2. Determine the total daily dose: 5 mL/dose × 2 doses/day (bid) = 10 mL/day.
  3. Calculate the total quantity needed for the duration of therapy: 10 mL/day × 10 days = 100 mL.

Question 2

A patient is prescribed Lantus SoloStar pens. The directions are to inject 35 units subcutaneously every evening. Each pen contains 3 mL of insulin at a concentration of 100 units/mL.

How many days will one Lantus SoloStar pen last the patient?

  1. 8 days (correct answer)
  2. 9 days
  3. 10 days
  4. 12 days
Explanation: The correct answer is 8 days.
  1. Calculate the total number of units in one pen: 3 mL/pen × 100 units/mL = 300 units/pen.
  2. Divide the total units per pen by the daily dose: 300 units ÷ 35 units/day ≈ 8.57 days.
  3. Since the patient cannot use a fraction of a day's dose from an empty pen, the pen will last for 8 full days. On the 9th day, a new pen must be started.

Question 3

A patient is prescribed Timolol 0.5% eye drops with instructions to instill 1 gtt into both eyes (OU) every morning. The pharmacy dispenses a 5 mL bottle.

Assuming a standard drop size of 20 drops/mL, what is the days supply for this bottle?

  1. 25 days
  2. 50 days (correct answer)
  3. 75 days
  4. 100 days
Explanation: The correct answer is 50 days.
  1. Calculate the total drops in the bottle: 5 mL × 20 drops/mL = 100 drops.
  2. Determine the total drops used per day: 'OU' means both eyes, so 1 drop/eye × 2 eyes = 2 drops/day.
  3. Divide the total drops in the bottle by the daily usage: 100 drops ÷ 2 drops/day = 50 days.

Question 4

A prescription for prednisone requires the patient to follow a tapering dose schedule:

  • Take 4 tablets daily for 3 days
  • Take 3 tablets daily for 3 days
  • Take 2 tablets daily for 3 days
  • Take 1 tablet daily for 3 days

What is the total quantity of tablets that should be dispensed?

  1. 10 tablets
  2. 12 tablets
  3. 30 tablets (correct answer)
  4. 40 tablets
Explanation: The correct answer is 30 tablets.
  1. Calculate the tablets for each step of the taper:
    • Step 1: 4 tablets/day × 3 days = 12 tablets
    • Step 2: 3 tablets/day × 3 days = 9 tablets
    • Step 3: 2 tablets/day × 3 days = 6 tablets
    • Step 4: 1 tablet/day × 3 days = 3 tablets
  2. Sum the tablets from all steps: 12 + 9 + 6 + 3 = 30 tablets.

Question 5

A patient is prescribed Fentanyl 25 mcg/hr transdermal patches. The directions are to apply one patch every 72 hours. The prescription is for a quantity of 10 patches.

What is the days supply?

  1. 10 days
  2. 24 days
  3. 30 days (correct answer)
  4. 72 days
Explanation: The correct answer is 30 days.
  1. Convert the dosing interval from hours to days: 72 hours ÷ 24 hours/day = 3 days. This means one patch lasts for 3 days.
  2. Multiply the quantity of patches by the duration of each patch: 10 patches × 3 days/patch = 30 days.

Question 6

A prescription for potassium chloride powder packets has the sig: 'Dissolve i packet in water and drink qd'. The quantity dispensed is 30 packets.

What is the days supply for this prescription?

  1. 15 days
  2. 30 days (correct answer)
  3. 60 days
  4. 90 days
Explanation: The correct answer is 30 days.
  1. The sig 'qd' means once daily. The dose is one packet per day.
  2. Divide the total quantity dispensed by the daily dose: 30 packets ÷ 1 packet/day = 30 days.

Question 7

A patient receives a prescription for ondansetron ODT 8 mg with the sig: 'i tab po q8h prn nausea'. The quantity is #15.

What is the days supply based on the maximum daily frequency?

  1. 5 days (correct answer)
  2. 7 days
  3. 10 days
  4. 15 days
Explanation: The correct answer is 5 days.
  1. The sig 'q8h' means every 8 hours. To find the maximum daily dose, divide the number of hours in a day by the dosing interval: 24 hours/day ÷ 8 hours/dose = 3 doses/day.
  2. The patient takes 1 tablet per dose, so the maximum daily usage is 3 tablets/day.
  3. Divide the total quantity dispensed by the maximum daily usage: 15 tablets ÷ 3 tablets/day = 5 days.

Question 8

A prescription for levothyroxine 100 mcg reads: 'Take i tab po qod'.

What is the days supply for a quantity of 30 tablets?

  1. 15 days
  2. 30 days
  3. 45 days
  4. 60 days (correct answer)
Explanation: The correct answer is 60 days.
  1. The sig 'qod' means every other day. This means the patient takes 1 tablet every 2 days.
  2. Multiply the quantity of tablets by the number of days each tablet will last: 30 tablets × 2 days/tablet = 60 days.

Question 9

A prescription for azithromycin 250 mg tablets is written for a 'Z-Pak'. The standard Z-Pak dosing is 2 tablets on day 1, then 1 tablet daily for 4 days.

What is the days supply for one Z-Pak?

  1. 3 days
  2. 5 days (correct answer)
  3. 6 days
  4. 7 days
Explanation: The correct answer is 5 days. A standard Z-Pak contains 6 tablets and is a 5-day course of therapy. The patient takes two tablets on the first day and then one tablet on days 2, 3, 4, and 5. This totals 1 + 4 = 5 days.

Question 10

A prescription is written for fluticasone nasal spray, 1 spray in each nostril daily. The product contains 120 metered sprays.

What is the days supply?

  1. 30 days
  2. 60 days (correct answer)
  3. 90 days
  4. 120 days
Explanation: The correct answer is 60 days.
  1. Determine the total sprays used per day: 1 spray/nostril × 2 nostrils = 2 sprays/day.
  2. Divide the total sprays in the device by the daily usage: 120 sprays ÷ 2 sprays/day = 60 days.

Question 11

A prescription for clindamycin 150 mg capsules reads: 'ii caps po qid for 10 days'.

What is the total number of capsules to dispense?

  1. 20 capsules
  2. 40 capsules
  3. 60 capsules
  4. 80 capsules (correct answer)
Explanation: The correct answer is 80 capsules.
  1. Interpret the sig: 'ii' means 2, and 'qid' means four times a day. So, the patient takes 2 capsules, four times a day.
  2. Calculate the total capsules per day: 2 capsules/dose × 4 doses/day = 8 capsules/day.
  3. Calculate the total quantity for the duration: 8 capsules/day × 10 days = 80 capsules.

Question 12

A patient is to receive enoxaparin 40 mg subcutaneously once daily for 14 days. The medication is available as 40 mg/0.4 mL prefilled syringes.

How many prefilled syringes should be dispensed?

  1. 7 syringes
  2. 10 syringes
  3. 14 syringes (correct answer)
  4. 28 syringes
Explanation: The correct answer is 14 syringes.
  1. The dose is 40 mg once daily, and each syringe contains exactly one 40 mg dose.
  2. Therefore, the patient will use one syringe per day.
  3. For a 14-day supply, the patient will need: 1 syringe/day × 14 days = 14 syringes.

Question 13

A prescription for gabapentin 300 mg has the following directions: 'Take 1 capsule at bedtime for 3 days, then 1 capsule BID for 3 days, then 1 capsule TID'. A quantity of 111 capsules is dispensed.

What is the days supply for this prescription?

  1. 34 days
  2. 38 days
  3. 40 days (correct answer)
  4. 42 days
Explanation: The correct answer is 40 days.
  1. Calculate the capsules used in the titration period:
    • First 3 days: 1 cap/day × 3 days = 3 capsules
    • Next 3 days: 2 caps/day × 3 days = 6 capsules
    • Total used in titration: 3 + 6 = 9 capsules
  2. Calculate the capsules remaining for the maintenance dose: 111 total caps - 9 titration caps = 102 remaining caps
  3. The maintenance dose is 1 capsule TID (3 times a day), so 3 capsules/day
  4. Calculate the days the remaining capsules will last: 102 caps ÷ 3 caps/day = 34 days
  5. Add the titration days to the maintenance days: 6 days (titration) + 34 days (maintenance) = 40 days

Question 14

A prescription is written for clotrimazole troches with the sig: 'i troche five times a day for 14 days'.

What is the total quantity of troches to be dispensed?

  1. 14 troches
  2. 35 troches
  3. 50 troches
  4. 70 troches (correct answer)
Explanation: The correct answer is 70 troches.
  1. Determine the number of troches used per day: 1 troche/dose × 5 doses/day = 5 troches/day.
  2. Multiply the daily usage by the duration of therapy: 5 troches/day × 14 days = 70 troches.

Question 15

A prescription for Nystatin Suspension has the following directions: 'Swish and swallow 5 mL qid'. A 240 mL bottle is dispensed.

What is the days supply?

  1. 12 days (correct answer)
  2. 15 days
  3. 24 days
  4. 30 days
Explanation: The correct answer is 12 days.
  1. Calculate the total volume used per day: 'qid' means four times a day. 5 mL/dose × 4 doses/day = 20 mL/day.
  2. Divide the total volume dispensed by the daily usage: 240 mL ÷ 20 mL/day = 12 days.

Question 16

A patient is prescribed methotrexate 2.5 mg tablets. The sig is 'Take 6 tabs po once weekly'.

How many tablets should be dispensed for a 12-week supply?

  1. 24 tablets
  2. 30 tablets
  3. 42 tablets
  4. 72 tablets (correct answer)
Explanation: The correct answer is 72 tablets.
  1. Identify the weekly dose: 6 tablets per week.
  2. Multiply the weekly dose by the number of weeks in the desired supply: 6 tablets/week × 12 weeks = 72 tablets.

Question 17

A patient has a prescription for warfarin with directions to take 5 mg on Monday, Wednesday, and Friday, and 2.5 mg on all other days of the week.

How many 2.5 mg tablets should be dispensed for a 28-day supply?

  1. 40 tablets (correct answer)
  2. 42 tablets
  3. 48 tablets
  4. 56 tablets
Explanation: The correct answer is 40 tablets.
  1. A 28-day period contains four full weeks.
  2. Calculate tablets needed per week:
    • MWF dose: 5 mg = two 2.5 mg tablets. 2 tablets/day × 3 days = 6 tablets.
    • Other days dose: 2.5 mg = one 2.5 mg tablet. 1 tablet/day × 4 days = 4 tablets.
    • Total per week: 6 + 4 = 10 tablets.
  3. Calculate total for 28 days (4 weeks): 10 tablets/week × 4 weeks = 40 tablets.

Question 18

A prescription for an albuterol HFA inhaler (200 inhalations/canister) has the following sig: 'ii puffs q4-6h prn shortness of breath'.

What is the days supply if the patient uses the maximum prescribed dose daily?

  1. 16 days (correct answer)
  2. 25 days
  3. 33 days
  4. 50 days
Explanation: The correct answer is 16 days.
  1. Determine the maximum number of doses per day. The shortest interval is every 4 hours (q4h): 24 hours/day ÷ 4 hours/dose = 6 doses/day.
  2. Calculate the maximum number of puffs (inhalations) per day: 2 puffs/dose × 6 doses/day = 12 puffs/day.
  3. Divide the total puffs in the canister by the maximum daily usage: 200 puffs ÷ 12 puffs/day ≈ 16.67 days. The supply will last 16 full days.

Question 19

A prescription reads: Metoprolol Tartrate 50 mg, i tab po bid. Dispense #60.

What is the days supply for this prescription?

  1. 15 days
  2. 30 days (correct answer)
  3. 60 days
  4. 90 days
Explanation: The correct answer is 30 days.
  1. Identify the number of tablets taken per day from the sig code 'bid' (twice a day): 1 tablet/dose × 2 doses/day = 2 tablets/day.
  2. Divide the total quantity dispensed by the number of tablets taken per day: 60 tablets ÷ 2 tablets/day = 30 days.

Question 20

A patient has a prescription for a 10 mL vial of Humalog insulin (100 units/mL). The patient's instructions are to inject 12 units before each meal (3 meals a day).

How many days will the 10 mL vial last?

  1. 21 days
  2. 27 days (correct answer)
  3. 33 days
  4. 36 days
Explanation: The correct answer is 27 days.
  1. Calculate the total units in the vial: 10 mL × 100 units/mL = 1000 units.
  2. Calculate the total daily dose: 12 units/meal × 3 meals/day = 36 units/day.
  3. Divide the total units in the vial by the daily dose: 1000 units ÷ 36 units/day ≈ 27.77 days.
  4. The vial will last for 27 full days.