How long cannabis lasts depends mainly on how it enters the body.
Smoked or vaporised
- the effect sets in almost immediately,
- is strongest after about a quarter of an hour,
- has largely worn off after two to three hours.
Eaten or drunk
- the effect comes on with a delay and often suddenly,
- in adults it peaks after one and a half to three hours,
- it lasts six to eight hours.
Anyone who still feels nothing after an hour and takes more gets the effect of both portions almost at the same time. How strong the effect is and how long it lasts also depends on the amount, the THC content, how you are feeling and your surroundings.
Worn off does not mean sober: even if you no longer feel anything, your fitness to drive may still be impaired. And cannabis can be detected for much longer than it has an effect.
Remember: Eaten, cannabis takes effect later and lasts much longer than when smoked. Do not take more.
More on this: What cannabis does in the body · Why do edibles take so long to kick in? · How long does cannabis stay in your system? · What does the 3.5 ng/ml limit mean?