The average time for Valium concentrations to peak in the blood is 1-1.5 hours. The absorption can be significantly delayed or dropped if diazepam is taken around the time of a fairly heavy meal. When food is consumed close to the dose, it can delay the absorption of diazepam for about 45 minutes compared to the 15 minutes it would take when no food is present. The initial distribution phase of Diazepam has a half-life of approximately 1 hour, although it may last for more than 3 hours. After that initial phase, there is a lengthy elimination phase for the half-life of up to 48 hours.

https://recoverypartnernetwork.com/drug/benzodiazepine/valium-addiction