Tips — drug calculations
Tips for drug calculations: 12 habits
Twelve simple habits that mean fewer careless mistakes and more right answers in your assessment.
12 tips that save marks
Small habits that mean fewer careless mistakes.
Read the question twice
The first time to understand it, the second to see what is asked for (mL, mL/h, mg or number of tablets).
Write the units out
Write the unit beside every number in your working. It exposes mistakes straight away.
Convert to the same unit first
Dose and strength must be in the same unit before you divide. See unit conversion.
Do a sense check
Is the answer reasonable? 50 tablets is a warning sign.
Round last
Do not round intermediate results. See rounding.
Write down every step
Your steps can earn partial marks and help you find the mistake.
Use a memory aid
A simple memory aid for the main dose formula helps you start without hesitating.
Draw a picture for dilutions
A simple sketch shows what you have and what you want. See dilution.
Double-check the decimal point
Moving the decimal point is a common source of error.
Convert time to minutes or hours
Make sure the time is in the right unit for the formula. See infusion rates.
Practise against the clock
Practise a whole test within a time limit, so time is not a problem on the day.
Write down your most common mistakes
Keep a list and read it before your assessment.
Frequently asked questions
What are the best tips for drug calculation assessments?+
Read the question twice, convert to the same unit, write down every step and do a sense check of your answer.
How do you avoid careless mistakes?+
Write the units out in your working, do a sense check and practise under time pressure.
Should I round during the calculation?+
No, round last. Follow whatever your course specifies.
How do I practise the tips?+
Work through tests against the clock and correct your mistakes. There is a 14-day plan on the page on how to practise drug calculations.
Try the tips on real questions
The tips only help once you use them. Take a test in Dos and see whether the sense check saves you marks.
