Urinalysis is the most common test type for drug testing. Detection of a drug in the specimen is mostly dependent on the detection period and the cutoff levels. Detection period means up to how many days the drug testing can reveal the presence of drugs in specimen. The urine drug test results are matched with cutoff levels, which are already set up by SAMHSA.

Drug detection time depends on few factors like, time when drug is taken, frequency of use, type of specimen, drug testing method, and metabolism. The best time to detect the presence of drug in urine specimen is in the morning, as the chance of detecting drugs is more in morning when compared to other times.

According to LabCrop, the following are detection periods of few drugs which are identified in urine drug test. Approximate detection period for Alcohol is 3-5 days, 2-4 days for Methamphetamine, 7-14 days for Phenobarbital, 1 day for Codeine, 2 days for Morphine, 3 days for Methadone and 2-4 days for Cocaine.

Minimum concentrations of drugs or metabolites that should present in specimens are called as drug testing cutoff levels. Levels of drugs depends on few things like amount of consumption, frequency of use, metabolic use, body mass, age and overall health. SAMHSA has set up the cutoff levels which are used as standard in analyzing the test results. Cutoff levels are measured in nanogram per milliliter (ng/ml). If the test results are below the cutoff levels then test result is negative, if results are above cutoff levels then test result is positive.

According to About.com, the following are cutoff levels for some common drugs which are identified in urine drug test. Cutoff levels for Marijuana metabolites for initial drug testing are 50ng/ml and 15ng/ml for confirmatory drug test. For Phencyclidine (PCP) 25ng/ml is the cutoff level for both initial and confirmatory drug test. Amphetamines cutoff levels are 500ng/ml and 250ng/ml for initial and confirmatory cutoff levels respectively. Cocaine has 150ng/ml for initial and 100ng/ml for confirmatory cutoff levels. For any drug test, if results are below initial cutoff levels then lab reports it as negative. If the test results are above initial cutoff level then they can go for confirmatory test.

Drugs are detected when drug test is conducted on urine specimen, this test is easy to perform and result is known in minutes of testing. Detection time and cutoff levels of drug plays an important role in evaluating the results of drug test.