How pure are street drugs?

DrugWise infographic on the purity of street drugs (PDF)

There is no proper quality control over illegal drugs. It is often difficult to know whether a powder, pill, herb or liquid is a particular drug. Furthermore you may have no idea how strong the dose is or whether it contains other drugs or substances to bulk it out. Illegal drugs may contain:

  • Impurities – substances present in the drug as a natural result of how it was made rather than deliberately added. For example, opiate alkaloids may be present in heroin from refining opium into heroin.
  • Adulterants – these are drugs that deliberately mimic or enhance the effects of the drug being offered. Examples are the way caffeine and/ or ephedrine are often found in amphetamine or ecstasy.
  • Diluents – these are mainly sugars such as glucose, lactose and mannitol. These are added to bulk out the deal and assist the process of dilution of the drug for injection.

While impurities and diluents can be dangerous in themselves, the likelihood of dangerous substances added to drugs has often been exaggerated. Rumours have circulated about drugs cut with rat poison, strychnine and brick dust, but such contamination is rare. It is not in the dealer’s interest to have customers dying from deliberately contaminated drugs. In contrast people will return to get drugs from dealers who offer good quality substances.

Purity levels

Back in 2014 the Druglink street drugs survey contacted police forces, drug workers, treatment services, drug expert witnesses and members of the Drug Expert Witness and Valuation Association from around the UK. The survey reported rising purity levels for heroin, cocaine and MDMA, and this trend was found to have continued in the 2016 DrugWise Street Drug Trends Survey. 

Bearing these purity levels in mind it is important to adhere to harm reduction advice when using these drugs and start with small amounts, such as a quarter of a pill, and wait for an hour or two before considering using more.

Please note that this is a guide to national patterns and should not be relied on to determine the content of substances circulating in your area. The purity of street drugs varies between different areas and can change within a matter of days.


According to United Kingdom drug situation 2019: Focal Point annual report, the average amphetamine sulphate powder purity at user level has ranged between 5% and 12% over the past decade. The mean purity in England and Wales in 2018 was 11%.

Even in the peak years, roughly 1997-2000, purity levels never rose above 15%; more usually they settle between 5%-10%.

An informant to our Street Drugs Trend Survey 2016 from Liverpool said:

“The purity level which drug powders level out to is the lowest which dealers can get away with, i.e. the level at which they can make most profit before users stop buying it because it has gotten too weak or too adulterated to inject and/or smoke and/or sniff. This varies with the drug (its chemistry and related effects). With heroin that seems to be around 20% to 30%, while for amphetamine it is more in the range 5% to 10%.”


United Kingdom drug situation 2019: Focal Point annual report states that the mean purity of cocaine at user level in England and Wales decreased steadily from 51% in 2003 to a low of 20% in 2009. Purity has since increased to 63% in 2018, the highest level on record. This reflects high production rates in source countries and increased availability of cocaine across Europe.

Since powder cocaine is converted to crack in the UK, the trend in crack purity is similar to powder cocaine purity (though purities of crack are usually higher). The purity of crack at user level in England and Wales rose from its lowest point of 26% in 2011 to a record 77% in 2018 and has been over 70% since 2016.

The two tier market in cocaine continues with prices at ‘student’, ‘pub dust’ or ‘monkey dust’ purity (the name depends on location) at around 40% and costing about £30-£40 a gram going up to around £80 a gram for purity in excess of 70%.


The heroin drought of 2010 resulted for a while in low grade heroin on the streets, prior to this the purity was around 50%. Often cut with paracetamol and caffeine, purity levels were just 18% in 2011. Purity levels  This averaged out in the mid-teens to low 20%. By 2014, this had climbed in some areas to 40%. More recently as global heroin supply has increased and there’s been an increase in purity, at 46% in England and Wales in 2018.


As with cocaine and heroin, purity levels for ecstasy have increased but the amount of ecstasy in a tablet can vary greatly and tablets have been analysed and some contained no ecstasy but other drugs such as amphetamine or ketamine. Others have been found to contain some ecstasy but mixed with other drugs or a range of adulterants.Testing by organisation ‘The Loop’ concluded that in recent years – during and after the COVID-19 pandemic – there has been significant disruption to the MDMA market. They found the average pill strengths: 194mg in 2019, 157mg in 2021 and 167mg in 2022 and that in the summer of 2021, 45% of products tested were imposter drugs, containing no MDMA at all. In 2022 this had dropped to 11% suggesting that the market may have stabilised. More findings from The Loop’s testing can be seen in this recent article on Volteface.

Previously, in 2018, the mean purity of MDMA powder at user level in England and Wales was reported as 76% (United Kingdom drug situation 2019: Focal Point annual report).


Further information on drug purity is provided in the United Kingdom drug situation: Focal Point annual report 2019

Updated January 2023