Controlled Drug Classifications Under UK Law and Penalties

Under the Misuse of Drugs Act 1971, controlled substances in the United Kingdom are sorted into three classes — A, B, and C — with maximum penalties rising as the class gets more serious. UK drug classifications and penalties run from a two-year ceiling for basic Class C possession up to life imprisonment for producing or supplying a Class A drug, with unlimited fines available at every level.¹ The class a substance sits in decides the sentence a court can hand down, and the Home Secretary can move drugs between classes on the advice of the Advisory Council on the Misuse of Drugs.²

Class A Drugs

Class A is the most serious tier. The drugs people encounter most often at this level include heroin (diamorphine), cocaine, crack cocaine, ecstasy (MDMA), LSD, methamphetamine, and psilocybin-containing mushrooms.³ Fentanyl, methadone, and injectable morphine also sit in Class A.⁴

Some of these substances have legitimate medical uses under strict controls. Diamorphine is prescribed in palliative care, and methadone is widely used for opioid addiction treatment. The Class A label means unauthorised possession or dealing attracts the highest criminal penalties, not that no doctor can ever prescribe the drug.

Possession of a Class A substance carries a maximum of seven years in prison, an unlimited fine, or both. That maximum applies even to small amounts for personal use, though sentencing takes quantity, personal circumstances, and cooperation with authorities into account. Producing or supplying a Class A drug is treated far more severely: the maximum is life imprisonment alongside an unlimited fine.¹ This covers manufacturing, trafficking, dealing on the street, and offering to supply. Financial investigation orders often accompany these prosecutions, allowing authorities to trace and confiscate the proceeds of drug dealing.

Class B Drugs

Class B sits in the middle. Common substances here are cannabis, amphetamines, ketamine, codeine (outside low-dose over-the-counter preparations), and synthetic cannabinoids. Codeine occupies an unusual position: it is Class B in most forms, but very low-concentration preparations (no more than 100 mg per dose unit) fall into a less restrictive regulatory schedule and can be sold without a prescription.³

GHB, GBL, and the related chemical 1,4-butanediol were reclassified from Class C to Class B in April 2022 following ACMD advice about the risk of fatal overdose.⁵ Synthetic cannabinoids, sometimes sold under street names such as “Spice,” have been controlled as Class B since December 2016, with the legal definition broadened in 2019 to cover third-generation variants.⁶ Cannabis was briefly downgraded to Class C in January 2004 but moved back to Class B in January 2009.

Possession of a Class B drug carries a maximum sentence of five years’ imprisonment, an unlimited fine, or both.¹ In practice, someone caught with a small amount of cannabis for personal use will not always face prosecution. Police can issue a cannabis warning where the person admits the offence and the quantity is consistent with personal use; the drug is confiscated and a record is made, but a warning is not a conviction.⁷ Repeat offences or larger quantities push the case toward formal prosecution.

Supplying or producing a Class B drug carries a maximum of 14 years in prison and an unlimited fine.¹ Courts treat commercial-scale production and organised distribution networks far more harshly than a small-scale social supply between friends, though both are criminal offences.

Class C Drugs

Class C is the lowest tier, but “lowest” is relative. Possession without authorisation is still a criminal offence, and supply carries the same maximum sentence as Class B. Common Class C drugs include benzodiazepines such as diazepam and temazepam, anabolic steroids, and certain prescription sedatives.³

Nitrous oxide joined Class C in November 2023, making it illegal to possess for the purpose of inhalation to get high. The law draws a line between recreational misuse and legitimate uses in catering, medicine, and industry. If you are found with nitrous oxide, the burden falls on you to show you held it for a lawful purpose.⁸

Anabolic steroids have their own carve-out. It is not an offence to possess them for personal use.¹ Importing them by post or supplying them to others remains illegal, even if no money changes hands. That is the distinction that catches people out: buying steroids online from an overseas supplier and having them delivered is an importation offence, regardless of whether they are for your own use.

For all other Class C substances, possession carries a maximum of two years in prison, an unlimited fine, or both. Supplying or producing a Class C drug carries up to 14 years in prison and an unlimited fine, matching the Class B supply penalty.¹

Maximum Penalties at a Glance

Actual sentences vary widely based on the quantity involved, the offender’s role, and any previous convictions. The ceilings are:

Class A possession: up to 7 years’ imprisonment, an unlimited fine, or both.
Class A supply or production: up to life imprisonment, an unlimited fine, or both.
Class B possession: up to 5 years’ imprisonment, an unlimited fine, or both.
Class B supply or production: up to 14 years’ imprisonment, an unlimited fine, or both.
Class C possession: up to 2 years’ imprisonment, an unlimited fine, or both (anabolic steroids excepted for personal use).
Class C supply or production: up to 14 years’ imprisonment, an unlimited fine, or both.

A conviction at any level creates a criminal record. That record can affect employment, professional licensing, and travel to countries that refuse entry to people with drug convictions.¹

Temporary Class Drug Orders

New psychoactive substances appear on the market faster than permanent classification can keep up. The Police Reform and Social Responsibility Act 2011 gave the Home Secretary the power to impose a Temporary Class Drug Order (TCDO), banning a substance for up to 12 months while the ACMD investigates its risks.⁹ Parliament must approve the order within 40 sitting days, or it lapses.¹⁰

During a TCDO, producing, supplying, and importing the substance are all criminal offences, with a maximum of 14 years in prison and an unlimited fine on indictment, mirroring Class B.¹⁰ Simple possession is not a criminal offence while the order is in force.⁹ Police can still seize and destroy the substance, but a user will not face prosecution solely for having it. When the review period ends, the ACMD recommends either a permanent classification under Class A, B, or C, or removal of the controls if the evidence does not justify them.

Substances Banned Outside the A, B, C System

The Psychoactive Substances Act 2016 sits alongside the classification system. Instead of listing banned substances, it bans any substance capable of producing a psychoactive effect, then carves out exceptions for alcohol, tobacco, nicotine, caffeine, food, medicines, and drugs already controlled under the Misuse of Drugs Act 1971.¹¹

Under this Act, producing, supplying, offering to supply, and importing a psychoactive substance are all criminal offences. A person commits an offence if they know or suspect the substance is psychoactive and know or are reckless about whether it will be consumed for its mind-altering effects.¹¹ The maximum penalty for supply and production is seven years’ imprisonment. Simple possession for personal use is not a criminal offence, with one exception: possessing a psychoactive substance inside a prison or other custodial institution is an offence in its own right.

How Classifications Change

Drug classifications are not fixed. The Home Secretary can add, remove, or move substances between classes through a statutory instrument amending the schedules of the 1971 Act. Before making a change, the government normally asks the ACMD for a formal recommendation based on the latest evidence about a drug’s harms and patterns of misuse.² The government is not bound to follow that recommendation; when cannabis was moved back to Class B in 2009, the ACMD had opposed the change.

Recent amendments show how actively the system is maintained. GHB and related substances moved up to Class B in 2022.⁵ Nitrous oxide entered Class C in November 2023.⁸ A 2024 amendment order brought 15 new synthetic opioids and other substances under control.¹² If you are unsure whether a substance is currently controlled, the Home Office publishes an updated list of the most commonly encountered controlled drugs on GOV.UK.³

1
GOV.UK. Drugs Penalties
2
GOV.UK. About – Advisory Council on the Misuse of Drugs
3
GOV.UK. List of Most Commonly Encountered Drugs Currently Controlled Under the Misuse of Drugs Legislation
4
legislation.gov.uk. Misuse of Drugs Act 1971 – Schedule 2
5
GOV.UK. Circular 001/2022 – Reclassification of GHB and Related Substances
6
GOV.UK. Circular 009/2019 – Third Generation Synthetic Cannabinoids Update
7
Sentencing Council. Cannabis or Khat Warning
8
GOV.UK. 006/2023 – Control of Nitrous Oxide Under the Misuse of Drugs Act 1971
9
legislation.gov.uk. Police Reform and Social Responsibility Act 2011 – Explanatory Notes – Section 151
10
GOV.UK. Temporary Class Drugs Factsheet
11
legislation.gov.uk. Psychoactive Substances Act 2016
12
GOV.UK. Circular 001/2024 – The Misuse of Drugs Act 1971 (Amendment) Order 2024