this is a repeat of answer give by webmd health expert dr hoffman. i think this will answer your question. "alprazolam (xanax) is an anxiety-relieving medicine that starts to work within about an hour after taking the pill. the level of drug reaches a peak in the bloodstream after one to two hours and its felt effects last on average about 5 hours. however xanax remains in the bloodstream long after its anti-anxiety effects have worn off. xanax’s average half-life is 11 hours. this means that it takes an average of 11 hours for the body to eliminate half the xanax dose. in older or obese people or those with liver disease xanax’s half-life is longer as long as 40 hours. it takes several half-lives to eliminate a drug completely. so for most people there may still be a small fraction of xanax in your blood two days or more after taking a single pill. people who take xanax on a regular basis maintain a higher drug level in the bloodstream and it could take several weeks to eliminate all the xanax from the body. xanax is excreted from the blood into the urine and is detectable in drug tests. different drug tests have different sensitivities and may or may not detect a low level of xanax in the urine. " what does. 05 look like
first time taking perscribed xanax 0. 5 will show how long in your blood stream?