Most alcohol and drug-testing methods look for the chemicals that remain after the drug or alcohol breaks down. These are called the metabolites. The metabolites of drugs can be detected in blood, urine, hair, sweat or saliva. The most common type of testing is urine. The presence of drugs can be detected in urine for up to three or four days after use, although some drugs can be detected for up to 30 days after heavy use. They can be detected in blood for roughly the same period, and for an even shorter period in saliva. Most drugs can be detected in hair for up to 90 days. The most common drug testing package is a urine test for cannabis, cocaine, amphetamine, methamphetamine, benzodiazepine and opiates. Unlike alcohol testing, drug testing will not tell you whether a person is under the influence of a drug or the level of impairment. It will simply tell you whether the metabolites are present. With a blood test the plasma has to be separated before testing. Hair is more complex because it has to be washed and broken down.