According to the National Highway Traffic Safety Administration, Valium (also known as diazepam) has a half-life of about 43 hours, plus or minus 13. This means it would take about 86 hours, or 3 1/2 days, for it to be fully eliminated from the human body.
According to the Food and Drug Administration, the rate of elimination may be prolonged if multiple doses of Valium have been taken, as Valium tends to accumulate within the body. Although Valium has a half-life of about 43 hours, its metabolites are also medically active and have half-lives up to 100 hours long. This means that although all Valium may have been excreted by the body after three or four days, its metabolite N-desmethyldiazepam may still be circulating up to 200 hours, or eight days, after use.