How do you know if the shot is working?

The birth conrtol pill stops you from ovulating. Most women have much lighter periods while on the pill. You should have at least 1-3 days of spotting each month to reassure you that you are not pregnant, if you don't miss any pills. A blood test would indicate if there is enough hormone retained from the pills to have the desired result. If you keep careful track of body temperature and notice a slight drop around the time that you would expect to be ovulating, you might be ovulating. Dwight