People inject drugs for their own individual reasons, but there are some common themes:

• By injecting a drug, the effect will be more intense and immediate than if smoked or taken orally.
• A smaller amount of the drug is needed to get the same effect when injecting, and therefore, at first, it will work out cheaper to inject than to smoke.
• There is a `thrill' associated with the process of injecting (needle fixation).
• Some people find that injecting makes them feel less nauseous than smoking.

Injecting a drug is more risky than smoking or swallowing the drug as there is the likelihood of sharing injecting equipment, with the associated risk of HIV and many other infections. There is also a greater risk of overdosing.