In the United Kingdom, controlled drugs are those preparations referred to under the Misuse of Drugs Act 1971. The Act prohibits activities related to the manufacture, supply and possession of these drugs, and they are classified into three groups which determine the penalties for offences involving their misuse. Class A includes Alfentanil, COCAINE, DIAMORPHINE, dipipanone, methadone, MDMA (Ecstasy), MORPHINE, LSD, opium, phencyclidine, remifentanil, PETHIDINE and any Class B drug if given by injection. Class B includes AMPHETAMINES, BARBITURATES, CANNABIS and CODEINE as well as glutethimide, ketamine, nabilone, pentazocine, phenmetrazine and pholcodine. Class C includes drugs related to amphetamines, most BENZODIAZEPINES, tramadol and anabolic steroids and some others.

The Misuse of Drugs Regulations 2001 define the classes of person authorised to supply and possess controlled drugs in their professional capacity, and lay down the conditions under which these activities may be carried out. In the Regulations, drugs are divided into five schedules each specifying the requirements for supply, possession, prescribing and record-keeping. Schedule I contains drugs which are not used as medicines, such as LSD; schedules II and III contain drugs which are subject to the prescription requirements of the Act (see below). They are distinguished in the British National Formulary (BNF) by the symbol CD and they include morphine, diamorphine (heroin), other opioid analgesics, barbiturates, amphetamines, cocaine and diethylpropion. Schedules IV and V contain drugs such as the benzodiazepines and anabolic steroids which are subject to minimal control. Prescriptions for drugs in schedules II and III must be signed and dated by the prescriber, who must give his or her address. The prescription must be in the prescriber's own handwriting and provide the name and address of the patient and the total quantity of the preparation in both words and figures. The pharmacist is not allowed to dispense a controlled drug unless all the information required by law is given on the prescription.

Since 2015, it has been an offence in the UK to drive with certain controlled drugs above specified limits in the blood, regardless of whether driving was impaired. It will be a defence to show that the drug was prescribed for medical reasons, taken according to instructions and driving was not impaired. Essentially this includes the Class A drugs, ketamine, cannabis and amphetamines from Class B and most of the BENZODIAZEPINES in Class C.