A hair drug test determines patterns of alcohol or drug use over a period of time. In the private area, hair of any length can be examined. Hair that is 30 cm long can also be examined, which would then correspond to consumption about 2.5 years ago. The longer the hair, the higher the dilution factor and the less precise the result. In court (especially at the MPU) a maximum of 3 cm is permitted for alcohol and a maximum of 6 cm for drugs. Testers can also use hair analysis to search for a specific drug, or they can test a single hair sample for multiple different drugs or classes of drugs. Because drug consumption is versatile.