Question 1

Why does diazepam stay in your system so long?

Accepted Answer

Diazepam has an exceptionally long half-life of 20–100 hours. It is also metabolised into active metabolites — particularly desmethyldiazepam — which themselves have half-lives of 36–200 hours. This means diazepam and its breakdown products accumulate with repeated use and take weeks to fully clear.

Question 2

Will diazepam show on a standard drug test?

Accepted Answer

Yes. Benzodiazepines including diazepam are included in all standard UK drug testing panels. If you have a legitimate prescription, you must disclose this before testing — a positive benzodiazepine result with a valid prescription is generally acceptable in workplace testing.

Question 3

Does prescribed diazepam affect drug testing?

Accepted Answer

Yes. Prescribed diazepam will produce a positive benzodiazepine result on any drug test. Always inform the testing authority of your prescription. In most workplace drug testing contexts, a valid prescription explains a positive result — although some safety-critical roles may have stricter rules.

Question 4

Is diazepam safe to drive on?

Accepted Answer

No — not always. Diazepam impairs cognitive function, reaction time, and coordination. It is illegal to drive in the UK while impaired by diazepam. Even at prescribed doses, diazepam can impair driving ability. Patients are advised by their doctor not to drive until they know how diazepam affects them.

How Long Does Diazepam Stay in Your System?

Diazepam detection windows by test type

Detection times for other substances

Frequently asked questions