Research which legal medications can produce false positives for illegal drugs (see Resources below). Even some of the most common medications can make your drug test positive. Medications such as Dexatrim, Advil and Aleve are drugs that read positive for THC and Ecstasy. Skip those drugs for at least 72 hours before your drug test.
Talk with your doctor before taking your drug test. Fill out a detailed medication list of all over-the-counter and prescription medications to give to your doctor before your test.
Watch what you eat. Certain foods can deliver a positive reading on your drug test. If you eat anything with poppy seeds, such as bagels and muffins, change your dietary habits temporarily to get a more favorable test result. Eat plain bagels or blueberry muffins until after your drug test.
Ask for a different type of drug test if you've gotten multiple false positive results. Get tested through saliva, hair or sweat samples to see if the results change.
Discuss your results with your doctor and look into why your test results came back positive when you don't take drugs. Doctors use gas chromatography or mass spectrometry to get in-depth results of your sample by breaking down its components differently. Once those results come back, you'll know for certain your true drug test results.