There are a number of tests that can be used to detect Ativan in the system:
A urine test can be used to detect lorazepam in urine for up to 6 days. The period may extend to a week in case of long term users. Metabolite lorazepam glucuronide tends to stay in the system for much longer so it may be detected for up to 9 days in the urine. You may consult a rehab expert and know how long does Ativan stays in your urine.
Urine tests are a preferable choice since they are non-invasive and easier to perform.
Blood can also be tested for the detection of lorazepam. The drug becomes detectable in the blood within 4-6 hours of the ingestion and can be detected for up to 3 days. However, for long term and frequent users, the drug may last longer than 3 days. A rehab specialist would be in a best position to answer as to how long does Ativan stays in your blood. Due to their invasive nature, blood tests are rarely used to detect Ativan.
A strand of hair, usually for head, is taken and tested for Ativan. The minimum length of the hair required for these types of tests is 3cm. Hair tests are effective up to 4 weeks so they can be used to find out a former Ativan user even when he has not taken the drug in weeks.
Saliva tests can be taken for up to 7 hours of last drug use. They are only effective for short term testing. They are non-invasive but still, they tests are seldom used.