I took about 18 mgs of lorzapam two weeks ago will it still show in a urine drug test?

No: benzodiazepines, like lorazepam, have a short half-life (time in the body). Most last only a couple of days. More importantly, if you are properly taking a prescribed medication there won't be any problem with having it show up in a drug screen.

18 mgs all at once?: That is a lot of lorazepam. What was the reason that you took so much? Was it a suicide attempt or drug abuse? In either case, it sounds like you may more important things to worry about than passing a drug test. If you mean that you had taken 18 mgs over a period of time and have not taken any in 2 weeks that is a different story, and it will probably not show up on a urine drug screen.

At one time???: If you took 18 mg of lorazepam in one day, the least of your troubles is whether it will show up in a drug screen (the answer to which depends to some extent on your particular metabolism, and to a larger extent on the sensitivity of the test they are using). That is in overdose territory, and indicates a dangerous use of medications. Talk to your doctor or a mental health professional SOON.