Are you male? You're on birth control?
Well I'll assume you are a guy not on b/c. No it won't affect yours or whoevers birth control.
I can't speak to whatever its going to do for you tho - the results will be more dependent on how tight your diet is. The shakes are going to be dependent on how much you take and how well you handle it. Whatever you expect as far as "I want it to work" -- it again will depend on how tight your diet is, but still don't expect amazingly great things from it. It only improves your fat burnign slight more than your standard OTC thermos.
Best way to start it is w/ 1 pill (what is it ... 20 mcg?) - on the morning of your first day. If you don't feel the sides much, go ahead & add another on in the mid afternoon. See how that goes. The next day, add 1 to the morning dose. If that's' ok, add another to the afternoon dose. IF that's ok, add another one in the morning. People tend to just keep increasing it a bit each day for the 2 weeks. Then take 2 weeks off. Just have to find where it really gets to be too much for you. Then you can back down by 1 pill or just stay at that dose. Your body will build up a tolerance so you will need to add more each day to "feel it". Then take the 2 weeks off to clear your receptors & start over. You can take an ECA / thermogenic on the off 2 weeks.