Renton and Dianne smoke hashish in Renton's flat
The film is about drug addiction.
Characters are shown drunk or getting high because of drugs.
There are frequent depictions of the characters preparing drugs, including scenes of them heating the drugs over a flame, tying their arms with belts and injecting the drug into their veins.
While such scenes are frequent, the film does not promote or glamourise drug abuse.
There are a few drug induced hallucinations in the film as well.
All characters smoke and drink and several scenes take place in bars.
A character shoves a Morphine suppository up his anus and accidentally defecates it into the toilet and has to retrieve it by going into the toilet, which leads to an oddly fantastical sequence in the toilet waters.