What does a THC test measure?

Urine tests cannot prove that someone is stoned. Urine tests only detect breakdown products of THC in the urine. It is not possible to find out when the actual consumption took place. Nor can it be read off how much someone has smoked. It goes even further: hemp beer or hemp cooking oil can also lead to positive urine samples (there are also traces of THC in these products, which the very sensitive tests then detect), just as the consumption of cough syrup or even poppy seed rolls can lead to positive morphine results. These tests are therefore not conclusive.

Particularly problematic with THC tests is the fact that THC degradation products can be detected for an extremely long time (weeks to months) after consumption. This means that the person tested has long since sobered up, but the test still shows positive. With hard drugs like cocaine or alcohol, the detection time is much shorter.

Urine tests that can detect THC breakdown products “yes/no” are already available for under 20 francs. The simple tests can be done by anyone: Put some urine on the test strip, wait, see if it indicates positive or negative. Usually, such a cheap test is done first (there are also some for hair, sweat and saliva). If this is positive, it is checked with a more expensive (blood) test.

However, the quantitative tests (which search for THC in the blood and can indicate the amount of THC in nanograms per milliliter of blood plasma) must be performed in a specialized laboratory. This can be done in private diagnostic laboratories or in the Institute of Forensic Medicine (these tests are specifically estimated in court). The blood tests reveal much more information: not only is a THC breakdown product measured (as in the urine test), but one or two effectively psychoactive THC variants can also be determined. Such tests cost several hundred francs.

While you can sometimes cheat on urine tests (you can bring in someone else's - THC-free - urine; you can take drugs that can interfere with certain tests), there's no way around blood tests. By the way, all test regulations also say that urine excretion must be observed (so concretely: someone must watch you urinate into the glass and thus check that the urine is really yours - but it is not always handled that way and opens up possibilities for manipulation).

More and more new tests are entering the market - it seems lucrative to enable the control of people. Soon there will be chips that can detect cannabinoids - and not just once, but over and over again. This could dramatically reduce the cost of testing. Also in the works are several new devices that can detect the substances that drugs and explosives release into the air. These are vacuum cleaner-like devices that can be used to check handbags or backpacks for elevated levels, for example. Still in the planning stages are devices that can check entire corridors where people are moving. At the same time, one thing must be seen: THC is very easy to detect…