The half-life of a drug is the time it takes for the amount of it in your body to be reduced by half. This depends on how the body processes and gets rid of the drug, and can vary from a few hours to a few days.
No matter what dosage of a particular drug you're on or how long you've been taking it for, its half-life is always the same.
Why does my medication's half-life matter?
A drug's half-life matters because usually:
- a short half-life = more withdrawal problems
- a long half-life = fewer withdrawal problems
So if you're taking a drug with a short half-life and having problems with withdrawal, it might be possible for you to switch to a related drug with a longer half-life, which could be easier to come off.
You can find out the half-life of a specific drug by looking it up in our drugs A–Z. You can also compare the half-lives of different types of drugs by looking at the comparison tables for:
The half-life given for any drug is not an exact figure and, in practice, it can vary a lot between individuals.
This information was published in 2016. We will revise it in 2018.