There is a good chance you will not be tested for it. Benzodiazepines (the drug class Valium is in) is not part of a basic 5 panel drug test. It must be added on. Some employers will add on benzodiazepines or they might add barbiturates, oxycodone, something else, and commonly they will NOT add other tests on.
Most likely you will pass but of all the benzodiazepines you can take Valium is most easily detectable and it is detected for a long time compared to other benzodiazepines. The half-life of diazepam (Valium) is about 24hrs but diazepam has many active metabolites that are benzodiazepines that have a half-life of about 100hrs. Having said that in the real world you should not have a problem. And don't try to "flush" your system or anything to dilute or change urine. Many tests can detect abnormalities in the urine like an unusually low concentration and the sample can be flagged and failed.
By the way, I am really curious why you would take Valium within a few days of a drug test? I mean no disrespect I just don't see why people do that.
Source(s):
I am a medical student at a university in Montréal, QC, Canada for psychiatry and internal medicine. I have a Hons. BSc in pharmacology and I have interned with two psychiatrists, one neurologist, and at a chemical dependency rehabilitation centre. In addition, I have worked as a pharmacy assistant.
and I have taken Valium