This section includes information about units, converting dosage units and the basic calculation skills you need as a prescriber. There are lots of activities to test your understanding and give you an opportunity to practice calculations for common scenarios encountered in practice. The most common type of medication error is using the wrong dose, strength or frequency so it is key to get these basic principles right, first time, every time. See the section on medication errors for more detail on this important area.

The Prescribing Skills Assessment (PSA) exam also includes questions on calculation skills so practicing these will help you prepare for the exam. It is worth noting under normal circumstances you would not have time pressure to complete calculations and in practice you should take your time and get a second check if unsure

Using unit abbreviations

Units of Lantus

Unit abbreviations

Look at the real example to illustrate the use of units of Lantus (a type of long-acting insulin) - is it 100 units or 10 units?

A note on decimal points; where possible avoid using fractional doses e.g. levothyroxine 0.05mg should be written as 50 microgram or digoxin 0.125mg should be written as 125 micrograms. Never use decimal points unnecessarily e.g. bisoprolol 5.0mg. Sometimes you may need to convert between imperial measurement and the metric system. These are included in the table below for information (e.g. in paediatrics parents will often talk about ounces (oz) of milk in feeds so you would need to know how this converts to mls).

Take great care with decimal placement as incorrect conversion can result in 10 to 100 fold errors which could prove fatal.