In brief
- Energy Control, the drug checking service run by the Asociación Bienestar y Desarrollo (ABD), has published “Hidden Substances,” a report compiling ten years of its own testing data.
- Out of 29,865 samples analyzed between 2016 and 2025, 71.5% contained no adulterants; 21.3% had added substances, and 5.9% were completely substituted.
- Heroin (83%) and mephedrone (70%) topped adulteration rates; LSD (6%) and MDMA (8%) were the least frequently adulterated substances.
Few snapshots of Spain’s illicit drug market are as detailed as the one just published by Energy Control. The harm reduction organization’s drug checking service compiled a decade of laboratory findings—29,865 voluntarily submitted samples tested between 2016 and 2025—to answer a straightforward question: when someone buys a drug, what is actually in it?
Addition and substitution are not the same thing
The report begins by clarifying a common misconception. One issue is adulteration by addition: the sample contains the expected drug alongside added substances. Quite another is total substitution: the lab analysis reveals something entirely different from what the buyer believed they purchased—a scenario carrying greater risk because the user has no idea what they are taking. With that distinction established, the decade’s figures break down as follows: 71.5% of samples contained no added substances, 21.3% showed addition, and 5.9% turned out to be complete substitutions. Among adulterants, caffeine was by far the most prevalent, followed by levamisole, phenacetin, and local anesthetics.
Vast differences across substances
The report’s most actionable finding is that adulteration is not distributed equally. At the high end are heroin, with 83% of samples adulterated, and mephedrone (4-MMC) at 70%, followed by amphetamine (60%), 3-MMC (49%), and cocaine (42%). At the lower end are LSD (6%), MDMA (8%), and methamphetamine (5%), with ketamine at 15% and 2C-B at 25%. Energy Control also highlights an emerging trend that has solidified since 2022: synthetic cathinones such as 4-CMC, 3-CMC, and 2-MMC increasingly appear as adulterants in other substances. Adulteration is not necessarily more frequent than in the past, but it has become chemically more diverse and less predictable.
What this means
These figures should be read with an important caveat: they come from a voluntary drug checking service, not a randomized survey of drug use in Spain. Someone who submits a sample for testing is already cautious about what they consume, and that profile may not reflect the wider market. Even so, ten years and nearly 30,000 samples reveal robust trends, and the practical takeaway is clear: the only reliable way to know what a substance contains is laboratory testing—the exact purpose of these services, funded in part by Spain’s National Drug Plan. The growing complexity of adulterants reinforces this need, as novel compounds cannot be identified by sight or taste. You can learn more in our guide to harm reduction and responsible use, as well as our coverage of the synthetic opioids test strips fail to detect, a prime example of why lab analysis remains irreplaceable.
Source
- Energy Control (ABD). Sustancias ocultas: clasificación, prevalencia y riesgos de los adulterantes de las drogas consumidas con fines recreativos. Energy Control, May 29, 2026.
Educational content written from a harm reduction perspective and with respect for individual freedom. It is not a substitute for advice from a healthcare professional and is not intended to encourage or condemn any drug use.
