Drug Driving Limits

Drug Driving Legal Limits.

The government have set limits for drug driving for 16 drugs as follows –


Benzoylecgonine – 50 µg/L

Clonazepam – 50 µg/L

Cocaine – 10 µg/L

Delta-9-Tetrahydrocannabinol – 2 µg/L

Diazepam – 550 µg/L

Flunitrazepam – 300 µg/L

Ketamine – 20 µg/L

Lorazepam – 100 µg/L

Lysergic Acid Diethylamide – 1 µg/L

Methadone – 500 µg/L

Methylamphetamine – 10 µg/L

Methylenedioxymethamphetamine – 10 µg/L

6-Monoacetylmorphine – 5 µg/L

Morphine – 80 µg/L

Oxazepam – 300 µg/L

Temazepam – 1000 µg/L

See the individual pages for more details.

Details of the drugs are as follows-


Are a class of drugs used to treat anxiety and epilepsy, as well as muscle spasm and insomnia.

Clonazepam is used to treat epilepsy and is marketed as Rivotril

Diazepam is the most commonly marketed benzodiazepine drug, it is used to treat anxiety , sleeplessness , muscle spasticity, acute alcohol withdrawal, epilepsy and is also used during surgery as part of the pre-med however it is also misused due to its sedative effects.


Also known as “roofies” or Rohypnol. It was previously marketed for the short term treatment of extreme insomnia, however it is not commonly used in the UK , and no current licenced medical preparations are marketed in the EU as of 2015.

Other Benzodiazepines include

Temazepam, Oxazepam, Lorazepam and Nitrazepam all have broadly similar effects


Cocaine has few legitimate medical uses having been largely been superseded by more modern and safer drugs with less potential for misuse,

It is a powerful nervous system stimulant. Its effects can last from fifteen to thirty minutes, to an hour. That is all depending on the amount of the intake dosage and the route of administration. Cocaine can be in the form of fine white powder, bitter to the taste. When inhaled or injected, it causes a numbing effect. Crack cocaine is a smokeable form of cocaine made into small “rocks” by processing cocaine with sodium bicarbonate (baking soda) and water. Cocaine increases alertness, feelings of well-being and euphoria, energy and motor activity, feelings of competence and sexuality. Cocaine’s effects are very similar to that of amphetamine, however cocaine’s effects tend to be much shorter lasting, but more prominent. Cocaine causes psychological dependence, and leads to desire to repeat the dosing.

Amphetamine, Methylamphetamine and Phenylethylamine are stimulants and potent central nervous system (CNS) stimulants that is used as a recreational drug and, rarely, to treat attention deficit hyperactivity disorder (ADHD) and obesity.


Recreationally, methamphetamine is used to increase sexual desire, lift the mood, and increase energy, all cause increased alertness aggression and can lead to high blood pressure and cardiovascular accidents

Hallucinogenics and delerients

Delta-9-Tetrahydrocannabinol is the principal psychoactive constituent of cannabis. THC has mild to moderate analgesic effects, and cannabis can be used to treat pain. Other effects include relaxation, alteration of visual, auditory, and olfactory senses, fatigue, and appetite stimulation. THC is effective against vomiting and nausea.


Methylenedioxymethamphetamine (MDMA)

MDMA is a euphoric drug, widely known as Ecstasy or E. It causes sedation and a warm euphoria. In overdose it can cause delirium and agitation, Deaths have been reported due to convulsions and other effects


Ketamine is a medication used mainly for starting and maintaining anaesthesia. Other uses include sedation in intensive care, as a pain killer, as treatment of bronchospasm, as a treatment for complex regional pain syndrome and as an antidepressant.

Ketamine is very short-acting. It takes effect within about 10 minutes, while its hallucinogenic effects last 60 minutes when inhaled or injected and up to two hours when ingested orally. It may be misused and produces a dissociative state where the user experiences auditory or visual hallucinations.

LSD 25 or Acid

LSD is a powerful hallucinogenic, causing visual and auditory hallucination. It may render the user unable to function normally for up to 12 hours, but most users report shorter effects, It is a class 1 controlled substance which has no legitimate use in medicine

Methadone and opioids (Morphine, Heroin & Codeine)

Methadone treatment may impair driving ability. However, there have been multiple studies verifying the ability of methadone maintenance patients to drive. It is used to treat & manage opioid  withdrawal

Morphine and codeine are used to treat moderate to severe pain and often cause drowsiness and nausea in patients.

All opioids have the potential to cause dependence and addiction and the initial “high” is often lost as tolerance and dependence increase.

Drug Driving Limits

Unlike alcohol there is not one set drug driving limit, it varies from drug to drug. There are two reasons for this, firstly because unlike alcohol a number of these drugs are illegal. There are effectively two options in terms of the level, it could be set at a level to protect road safety or at a zero tolerance level. The alcohol limits are set at a road safety limit, that is to say the Government consider that it is not safe to drive above the limit set. The government were keen not to set a legal that appeared to allow a tolerance of illegal drugs. There are then two types of limits within this law, the first is aiming at zero tolerance and this relates to the illegal drugs. The law allows for some ‘accidental’ consumption of the drug either by inhaling secondary smoke as in the case of cannabis or because the drug may appear in legal drugs. The second type of limit such as for Morphine or Temazepam is set at a level that the Government consider it safe to drive.

This presents a difficulty for people who are taking a prescribed drug that is mentioned on this list. The law allows a defence if it can be shown it was prescribed or supplied for medical or dental reasons. It will still be an offence unless the drug is taken in accordance with the instructions. It can still be an offence under the old law, which remains, if you are unfit to drive through the drug whether or not it is prescribed.


If you have been charged or arrested for this offence and would like free initial advice call our expert drug driving team on 01623 600645.