Hi doctor usually how long it will take to get back periods if regestrone 5mg tablets is used (twice/day) for 3 days?

It depends. It depends on why you are skipping periods. If you have adequate estrogen, aren't pregnant, and don't have an anatomic blockage to the outflow tract,You should start bleeding within a week after finishing the progestin. Rarely it can take up to 2 weeks. Hope this helps.