The length of time it takes for the birth control to become completely effective as a sole contraceptive varies depending on the type of pill you use and when you start the packet of pills. Your healthcare provider should be able to tell you exactly when the particular version of the pill you have been prescribed becomes fully effective against pregnancy. Also, if you are taking other medications such as antibiotics, they can affect the effectiveness of the contraceptive pill and your doctor may recommend that you use an additional form of protection. Similarly, stomach upsets such as sickness and diarrhoea can affect the absorption of the pill, so again using an additional method such as a condom can help make sure pregnancy doesn't occur. It is worth bearing in mind that using condoms as well as the birth control pill can protect both you and your partner from STDs as well as providing extra protection against pregnancy.
Some women do experience some side effects as a result of using the birth control pill.
However, these side effects can vary from woman to woman. When you visit your health care provider to obtain a prescription for the contraceptive pill they should ask you a few questions about your medical history. This helps them to make sure that they prescribe the type of pill that is best suited to you and hopefully reduce the possibility of any adverse side effects. Serious side effects are rare, but if you do experience any problems such as headaches or skin problems it is worth going back to see your healthcare provider as they may be able to change your pill for a different one. If a woman has missed a pill the risks of pregnancy will depend on the type of pill she is on.