Q and A

Question

How are the words ‘rare’ and ‘common’ defined for side effects?

Answer

The EMA (the European drug regulatory agency) has very specific definitions for words relating to frequency of side effects.

This is a good question because the words are often used wrongly.

This is shown in the table below: ie

  • Very common affects more than 1 in 10 people – ie the risk is 10% or higher
  • Common affects between 1 in 100 and 1 in 10 people – ie risk is 1% to 10%
  • Uncommon affects between 1 in 1,000 and 1 in 100 people – ie risk is 0.1% to 1%
  • Rare affects between 1 in 10,000 and 1 in 1,000 people – ie risk is 0.01% to 0.1%
  • Very rare affects less than 1 in 10,000 people – ie risk is less than 0.01% (This includes isolated reports, or where the absolute risk is not known or can’t be quantified. For example, if identified through post-marketing safety surveillance and the frequency cannot be estimated from the available data).
Term Numerical rate Percentage rate
Very common More than 1 in 10 10% or higher
Common 1 in 10 – 1 in 100 10% – 1% 
Uncommon 1 in 100 – 1 in 1000 0.1% to 1%
Rare 1 in 1000 – 1 in 10,000 0.01% to 0.1%
Very rare Less than 1 in 10,000 Less than  0.01%

2 comments

  1. Roy Trevelion

    Hi 2, Thanks!

  2. 2

    What’s up to every one, the contents existing at this site are genuinely remarkable for people experience, well, keep up the nice work fellows.

Comment

Your email address will not be published. Required fields are marked *