How long does diazepam withdrawal last?

Long. Valium has a long half-life in your system (diazepam is 30—60 hours), and metabolic breakdown products of that last longer -- some up to 100 hours. This means that withdrawal symptoms can start within 5 days to 14 days, but can be delayed for up to 3 weeks (because of the breakdown products). You may need some medical help during this, because withdrawal from benzodiazepines can cause seizures.