Urine drug screening is  a procedure when one needs to provide a sample of urine. Employers do not want to give a job for employees with a drug problem. Drug addicted are prone to stealing and lying. However, the most drug addicts are not robbers but employers do not want to give them any chances. Drug screenings are expensive. Some organisations are eager to pre-screen job applicants. Urine drug screenings are simple and quick.
Some people try to disorder a urine test by drinking a lot of water. The diluted urine may be rejecting due to its clear color. Specimens  that are too clear may tested for specific way.

  If the sample fails the specific gravity test, the sample is rejected and the dilution is reported to the entity that ordered the test. Some herbal extracts and diuretics, such as goldenseal, are sold as a quick detox from controlled substances, but their efficacy is doubtful. Some types of urinalysis can even detect the use of these detox substances. One of the methods to test for adulterants is to add small portion of an actual drug and then retest that portion. If a masking agent is present in the urine, the resulting drug test will have a negative result despite the fact that a drug was added. This situation is also usually reported to whomever ordered the test.

  Urine drug screenings can just detect drug use for the last three days. Occasional drug users may be able to pass a drug test successfully. On the other side, habitual drug users may have a sign of drugs in their body after a period of a three day. Using cocaine for a long time, for example, may have traces of this drug in their body for up to 120 days. Persons who attempt to take urine drug screening may consider detoxifying their body days prior to taking the test. Certainly, detoxification products may be easily detected on the drug test.

    What's tested for?
• Amphetamines. This type of drugs consists of methamphetamines, racemic amphetamines, dextroamphetamines. Many legal substances such as phentermine, phenylephrine, ephedrine, pseudoephedrine and phenylpropanolamine can be a higher incidence of false positives. As for selegeline it usually causes positive result.
Near a half of the amphetamines and methamphetamines are excreted unchanged in the urine. Various analysis are used to detect the presence of either.
• Barbiturates. Some of this drugs are unaltered in the urine and some assays are effective in detecting their presence. There is no significant case of false positives.
• Benzodiazepines. Many analysis are examined with either nordiazepam or oxazepam cause these are common metabolites of other benzodiazepines. There are few laboratories which screen for anything other than nordiazepam or oxazepam.
• Cannabinoids. The psychoactive substance in marijuana delta-9-tetrahydrocannabinol, usaually called THC becomes a psychoactive substance of the P450 system. Assays typically screen for THC and its metabolites.
Cocaine  It is metabolized in the serum and liver. Cocaine is converted in the blood to ecgonine methyl ester  and benzoylecgonine. Both of these metabolites are excreted in the urine. Typically, assays target benzoylecgonine.
• Opiates.  This type of drugs is metabolized mainly in hepatocytes but also in the CNS, placenta, lungs and kidneys. Opiates are excreted primarily in the urine unchanged as are many of their metabolites.
• Phencyclidine - is hydroxylated and then glucuronidated to be excreted in the urine. In addition about 15% is excreted unchanged. Very few things will cause a false-positive PCP.