Birth control pills, when take correctly are about 99% effective though they aren’t foolproof. You need to take them regularly as prescribed – even when you aren’t sexually active.
For example, mini pill (only hormone is progestin) needs to be taken at the same time every day otherwise you can get pregnant. If you happen to forget to take your pill and are even 3 hours late, you will need to use backup birth control such as a condom to prevent pregnancy.
If you have just started taking the pill, it will take several days to work. You will need to use backup contraceptives like condoms until the pill has time to work. Ask your doctor how many days you should use backup contraceptives when starting the pill.
There are other reasons the pill can fail other than forgetting to take them:
Improper Storage – don’t keep them in your bathroom. They should be stored at room temperature and kept away from heat and moisture.
Conflicting with Other Medicine – there are several types of medicines that can make the pill less effective. Always tell your doctor you are taking the pill to make sure the medicines don’t counteract.
Herbal Supplements – garlic pills, flax seed, St. John’s wort are among some of the herbs that can reduce the effectiveness of the pill. Be sure to talk with your doctor if you plan to start taking any herbal supplements.
Vomiting and Diarrhea – if you have the stomach bug and are vomiting or are hit with diarrhea, your pill may not have enough time to be absorbed into your body.
If you are on the pill and have unexpectedly missed your period (you won’t get your period with some pills) or have early signs of pregnancy, take a pregnancy test and call your doctor right away.