Day Supply Calculations for the PTCB Exam

Tablet and Capsule Day Supply

Day supply calculations determine how long a prescription will last. For tablets, divide the quantity dispensed by the number of tablets taken per day. If 90 tablets are dispensed and the patient takes 1 tablet three times daily, the day supply is 90 / 3 = 30 days.

For liquid medications, calculate the total daily volume consumed, then divide the total volume dispensed by that daily amount. If a patient takes 10 mL twice daily from a 300 mL bottle, the day supply is 300 / 20 = 15 days.

Inhalers and Insulin

Inhaler day supply is calculated by dividing the total number of actuations in the canister by the number of puffs taken per day. A 200-puff inhaler used as 2 puffs four times daily has a day supply of 200 / 8 = 25 days.

Insulin pens contain a set number of units. A pen with 300 units used at 30 units per day lasts 10 days. For insulin vials, 10 mL at 100 units/mL = 1000 units total.

Exam Preparation

Day supply questions are practical and frequently tested. Review with PTCB flashcards and practice under exam conditions with mini exams.