Lessons · Pharmacy · how many days the bottle lasts
How many days the bottle lasts
Days' supply is the quantity dispensed divided by the amount used in one day.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
What it is for
This is the number the insurance claim is built on. Put 30 days on a bottle that holds 20 days and the next fill comes back as refill too soon, with the patient standing at the counter and no medicine. Put 20 on a bottle that holds 30 and you have told the plan something that is not true.
How to think about it
Work out one day's worth first: the dose times how many times a day. Then divide the quantity by it. Days' supply always rounds DOWN to whole days, because a day the bottle cannot cover is not a day of supply.
Worked example
Amount a day = 5 mL x 3 = 15 mLThe dose times how many times a day.
Days' supply = 120 mL / 15 mL = 8 daysBottle divided by a day's worth.
60 tabs / (1 tab x 2 per day) = 30 daysTablets, the same arithmetic in one line.
100 tabs / 3 a day = 33.3, so 33 daysRound DOWN. Part of a day is not a day of supply.
Your turn
A 180 mL bottle with a sig of 10 mL three times a day. Write the days' supply.
180 / (10 x 3) = days
Solve one, graded on the server
The trap
Dividing by the dose and forgetting the frequency. 180 mL at 10 mL a dose is eighteen doses, and eighteen doses is only six days when three of them are taken every day.