Ask your own question now. Expert: Family Physician replied 2 years ago. Urine test for Ativan can be positive (it can be in your system) for approximately 5 days (not 72 hours). Drinking more water does NOT increase the rate at which the drug metabolites are removed from the body. Time is the only thing that is going to work. You need to be off Ativan for at least 5 days to get it completely out of your system and be certain of a negative test.