Heroin is a class A drug. This means that possessing it can lead to a prison sentence of up to 7 years and an unlimited fine. Supplying (which includes giving it to a friend) could lead to a life sentence and another unlimited fine.
As well as the legal implications of possessing and supplying heroin, those addicted to heroin may often become involved in other kinds of crime to fund their addiction. According to estimates by the Home Office, one third of all property crime in the UK is judged to be drug related, and those that take heroin, cocaine or crack represent higher reported levels of acquisitive offending than those who use other types of drugs, or who do not use drugs at all. This group commits very large amounts of shoplifting, burglary and other crime to finance drug purchases.