My drug screen results were negative, why? I take percocet and ativan (lorazepam) on a daily basis, my screen results did not find them in my system. Knowing that I take my meds daily, I cannot understand why they did not show.

Many possiblereasons. Oxycodone may not show up on a drug screen unless the screen is specifically geared to that drug. Ativan (lorazepam) should show up, but it depends on the dose. If you are on a low dose (0.5 mg a day) it may be negative. Also, if you are drinking large amounts of water, it dilutes your urine to where drugs may be below the detection limit of the test.
In . In short a few explanations; #1 your test gave a false negative result (possible but not very common) #2. The urine or blood was not yours (lab error, paperwork error, in short human error). #3 Percocet and Ativan (lorazepam) were not specifically screened for in the particular drug testing that was done (meaning although drugs in their class may cause a positive result, the biochemical make-up of Percocet and Ativan (lorazepam) may have not caused a positive reaction).