When constructing a drug testing program, either for use at home or in the workplace, it is vital that you educate yourself as to how long drugs stay in the system. Every drug, whether illegal or prescription, has a unique drug half life which determines exactly how long traces of the substance will remain present in the body. These periods of time range from just a few days, for prescription drugs like Valium and Xanax, to up to 3 months for potent strains of marijuana. It is crucial that anyone administering a drug testing program first learn about how long drugs stay in the system, because without this knowledge they will not know which testing methods to use or how often testing should be conducted. A number of external factors also influence how long drugs stay in the system, including the age, gender, height, weight, fitness level, and diet of the subject being tested. Knowing how these variables can affect the length of time that a drug stays in the system is the key to ensuring that your test results provide the clearest and most accurate picture possible.

The most commonly abused of the illicit drugs is marijuana, which stays in the system for an average of 4 weeks after the last usage. This range can vary, however, depending on the potency of the marijuana being ingested and the frequency of use. For first time users of marijuana, the drug stays in the system for only 3-4 days, while chronic users will have traces of THC in their bodies for as long as 3 months. Another popular recreational drug is cocaine, which stays in the system for 1-3 days after use. It is important to note that cocaine drug testing kits do not actually test for the drug itself, but rather for the metabolite which is produced by the body after ingestion. The cocaine metabolite stays in the system for up to 30 days after the last usage, and this should be used as the timeframe for cocaine testing. Opiate based drugs such as morphine and heroin typically stay in the system for only 2-4 days, which means opiate drug testing must be conducted often. Amphetamines will be present in the system for 2-5 days depending on the type being abused, while hallucinogens like LSD will only stay in the system for 1 day. Prescription painkillers such as Vicodin, as well as mood altering drugs like Valium and Xanax, will stay in the system for a period of 1-6 weeks. Each particular prescription drug has a different drug half life, so be sure that you know exactly which substance you wish to test for. Finding out how long drugs stay in the system is a necessity for any drug testing program to be efficient, affective, and accurate.