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.
How long it takes birth control to become effective depends on WHEN during your cycle you take the first pill. If you take the first pill on the first day of your period (as soon as you start bleeding) you are protected right away. If you take your first pill any other time, you will be protected after taking 7 pills. If you miss any pills or take them late during that 7 days you have to start the count over.