Urine tests became the prominent method for workplace drug testing after President Ronald Reagan issued Executive Order 12564 in 1986 for federal employees. Two years later, the Drug-Free Workplace Act of 1988 extended testing requirements to federal contractors and named urinalysis as the standard testing procedure.

Private Sector Testing

The law doesn't require private sector organizations to test for drugs, but it advises they can avoid legal complications by following the law's guidelines. Many companies have taken their cue from the federal government to institute urinalysis drug testing to promote a safe working environment, avoid hiring drug users and pay lower workers' compensation premiums.

Employer drug-testing programs may, however, be subject to state legislation. State law might mandate who pays for the test, for example. According to Small Business Services of San Antonio, New Jersey employers must pay for pre-employment drug tests except those for security guard positions, although in general, job candidates finance their own pre-employment testing. The Fair Labor Standards Act requires employers to pay employees for time spent getting a required drug test, even when it's one during non-work hours.

How Urinalysis Works

Urine drug tests indicate recent use of drugs; they do not confirm addiction or impairment. They detect metabolites, or drug residues that remain in the body. The minimum metabolite amount needed to test positive, the cutoff level, is set by the Substance Abuse and Mental Health Services Administration under the U.S. Department of Health and Human Services.

How long metabolites stay in the body, the detection window, varies by substance. According to the University of Illinois College of Pharmacy, the detection window for heroin is eight hours after use, while marijuana's ranges from three to 15 days, depending on frequency of use.

Test Procedures

Urine tests are either five-, eight- or 10-panel screenings. A five-panel test checks for amphetamines, marijuana and hashish, cocaine, opiates and phencyclidine, or PCP. Eight-panel tests measure traces of these five substances plus barbiturates, quaaludes and tranquilizers, or benzodiazepines, while 10-panel procedures add methadone and propoxyphene to the eight-panel list. If the initial screening is positive, a second confirmation test is done by gas chromatography/mass spectrometry, or GC/MS, a more accurate and expensive test.

False Positive Results

Some medicines and over-the-counter medications have molecular structures similar to the drugs targeted by urinalysis. Taking one can cause a false positive urine test. For example, the antibiotic amoxicillin creates a false positive result for cocaine. Weight loss drugs, Vicks inhalers, naproxen, dextromethorphan and pseudoephedrine also cause incorrect test results, according to the University of Cincinnati.

If you test positive, a medical review officer, or MRO, will contact you. Give this specially trained substance abuse doctor a list of all medications, herbal supplements and over-the-counter drugs taken before your urine test. The MRO can report you passed if he can confirm a medical cause behind the false reading. You have the right to request a GC/MS confirmation test if one was not already done before the MRO contacted you.

Employee Rights

Refusing to take a urine test equates to failing it for employees working under the auspices of the U.S. Department of Transportation. According to the legal website Nolo, employees of other firms may be unable to collect unemployment benefits depending on their state law.

Failing a urine test eliminates you as a job candidate if passing was a condition of employment. Nolo advises that some states only permit urine tests for new hires if a certified lab administers the test, all applicants for the position are tested and the employer informs the applicant in writing that drug testing is part of the screening process and a job offer is contingent on passing a drug test.