The levels of Lorazepam in the blood depend on the dosage administered. Lorazepam is known to have a short half-life of about 12 hours, which means that its level is reduced to half within 12 hours. Lorazepam is then excreted through the urine. For more information on Lorazepam, you can visit this site: http://www.drugs.com/pro/lorazepam.html
Lorazepam has a half-life of about 4 hours. This means that its content in your body decreases by half every four hours. It usually takes 3 days for it to completely be out of your system and not show up on a drug screen.