Passing a drug test can be a determining factor in obtaining employment. Many employers require prospective employees to take a drug test before offering employment as a way to weed out potential problems. According to the Drug Testing Network, over 80 percent of Fortune 500 companies require drug and alcohol testing of their current employees. Finding out the results of a pre-employment drug screen can take time, and there are several ways you can learn if you passed or not.

Pre-Employment Drug Screening

Pre-employment drug screening helps employers find out if applicants have recently used drugs. According to the U.S. Department of Labor, employers use drug tests to help deter employees from using drugs, identify those who have drug and alcohol problems, provide employees with a safe work environment, adhere to federal and state laws and regulations, and to benefit from discount programs offered by Workers' Compensation. If you must provide a drug test, you will usually give a urine sample at an approved lab or doctor's office within 24 hours of notification. Some employers may ask for a sample that will provide more in-depth information, such as with a saliva, blood or hair sample.

Drug Use Timelines

Employers typically use a five-panel street drug screen for potential employees. According to Drugs.com, this panel tests for marijuana, cocaine, PCP, opiates and amphetamines. Some employers may include some prescription drugs, such as oxycodone and barbiturates. Provide the lab with a list of current medications you are taking, particularly those prescribed by your physician. The amount of time it takes for a drug to get out of your system varies. Marijuana can take one to five days for infrequent users and up to 30 days for chronic users. Cocaine, amphetamines and barbiturates can take up to 96 hours and PCP up to seven days to leave your system.

Screening Turn Around Times

The turnaround time for drug testing results varies depending on several factors, so just because you have been waiting for several days does not mean you failed the test. The type of courier service the lab uses, holidays and weekends may have longer processing times. The time of day you submit your test may have an effect on the result time. A test given late in the day may come back later than one submitted in the morning. Negative results usually come back within one day of submitting it and positive results can take three to four days from the time the sample arrives at the lab.

Getting Results

Before the drug test, you sign a release so that your potential employer will have access to your results. Both you and the employer will receive a copy from the lab regarding whether you passed the test. Your results will probably come in the mail, while your employer will generally receive the results by courier or fax. If you prefer not to wait for the results in the mail, you may call the human resources department within two to three days to see if you passed the screening.