Birth control pills are a contraceptive drug used primarily to counteract impregnation, but it is also used by women who suffer from painful periods, or those who have their cycles at irregular times, among other uses. It is hormone based and can contain synthetic forms of either progesterone or estrogen, and in some cases even both.

Now for all advantageous uses for birth control pills, as with everything else it has some undesired side-effects. I'll list a few that commonly occur:

• Nausea - this side effect usually subsides after extended periods of taking the drug.
• Moodswings - as mentioned earlier, it is hormone based thus affecting one's mood.
• Gaining weight - this might be due to the body retaining fluids.
• Sensitive breasts - another side effect that usually subsides over time.
• Mild to heavy headaches - once again because it's hormone based.

There are of course more possible symptoms, but I think these are the most prominent ones.