Federal workplace drug testing was initiated during the late 1980s. Since then, numerous methods have been employed to subvert these drug tests, adulteration of urine samples being the most common. A wide variety of adulterants has been reported to date along with suitable methods of their detection. Recently, websites have claimed that zinc sulfate can be an effective adulterant to bypass drug testing. Herein, these claims are investigated using standard drug detection kits and urine samples adulterated with zinc. Drug-free urine samples were fortified with different amounts methamphetamines and benzoylecgonine, to which zinc sulfate was added to study its effect. Urine samples from acute marijuana smokers were also obtained in order to study the effects of zinc supplements on THC drug testing. All urine drug testing was performed using ELISA detection kits manufactured by Immunalysis. Both zinc sulfate and zinc supplements are effective in interfering with the detection of all three drugs by Immunalysis drug detection kits. Also, no suitable method could be established to detect zinc in urine samples. Zinc can be an effective adulterant in urine for some illicit drugs that are commonly screened under routine drug testing.