Generally, it takes between seven and 10 hours for a dog to digest food, but the many variables mean that only your vet can tell you how long it should be taking.
But how many days after Provera will your period start? When using Provera for amenorrhea (absence of menstrual periods) or abnormal vaginal bleeding, the medication is taken for 5 to 10 days. Menstrual-like vaginal bleeding usually occurs three to seven days after treatment ends.
1 For typical users, approximately 3 out of every 100 women using Depo-Provera will experience an accidental pregnancy in the first year. With perfect use, 1 out of every 100 women will become pregnant.  Depo-Provera starts working within 24 hours of the first shot if injected within 5 days of beginning a period.