What is the days supply for Humulin N insulin 20ml, if the dose is 40 U daily?
a) 100 days
b) 30 days
c) 60 days
d) 50 days
the book says the answer is d but, how did they get that?
I am taking the ptce tomorrow and i dont understand this question, can someone help?
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{ 2 comments… read them below or add one }
I stumbled on that question, as well.
I’m guessing that you’re using The Pharmacy Tehcnician: Workbook and Certification Review (Third Edition).
Working with the answer that the book gave you, you could have worked backwards to find out the amount of Humulin N to be dispensed.
Your first proportion would have been the following:
Humulin N units / 1 mL = x units / 20 mL
However, because the amount of Humulin N to be dispensed is "unknown," you have to work backwards.
The reverse calculations are as follows:
Set up your proportions using the book’s answer –
40 units / 1 day = x units / 50 days
You would have cross-multiplied [and divided by 1] and ended up with 2000 units.
Use your first proportion from earlier, where we can now fill in the "x" with "2000" -
Humulin N units / 1 mL = 2000 units / 20 mL
You would have ended up with 100 Humulin N units.
*Humulin N U-100 is usually the standard amount of Humulin N to be dispensed for medications.*
You should know that before taking the exam, just as you should know the concentrations of D5W, normal saline, etc.
From now on, if the amount to be dispensed is not given in a calculation problem, go with the most common, standard amount [so you won't have to work backwards].
Good luck!
You need to know how many U per ml of insulin to do this problem. I assume this info is provided for you somewhere in the class.
I googled "Insulin Units per Milliliter" and found that "in the U.S., most insulin is formulated at 100 units per milliliter" I plugged 100u/ml in, and it works in this example.
We know we have 20ml of insulin. We want to know how many days that will last a person who needs 40 units per day.
We need to know how many units are in 20ml. We know that in 1ml there are 100 units.
Using this conversion factor, we multiply 20ml x 100 units (cause 1ml is 100 units) and we find that we have 2,000 units available in our 20ml supply.
We know the patient needs 40 units per day, and we have 2000 units available. We want to know how many days that 2000 units will last at 40 units per day.
Divide 2,000 units by the daily dose of 40units, and we find that our patient has enough units in 20ml to last 50 days.