Plan B is a back-up form of birth control. It's purpose is to prevent pregnancy after contraceptive failure or unprotected sex. It can be purchased at a pharmacy without a prescription by individuals who are at least 17 years old. If you're 16 or younger, you must have a prescription from a doctor. Some women choose to keep the medication on hand at home in case of an unexpected situation, so they can take it immediately. Plan B, along with other drugs that have similar functions, are often referred to as morning-after pills or emergency contraception.
It's possible to get pregnant after using Plan B. When taken correctly, it's effective in preventing seven out of eight pregnancies that would have occurred (editor: see reference 1, the FAQ section on the site). However, it doesn't work if it's used after a woman has already become pregnant. Make sure that you follow the instructions for taking Plan B. If you're using the form that includes two doses, the second dose must be taken at the right time. Nausea and vomiting are common side effects. Contact a doctor or pharmacist for instructions if you vomit within 30 minutes of taking emergency contraception.
Plan B should be taken within 72 hours of having sex in order for it to be effective. The faster you take it, the more likely it is to prevent a pregnancy. Emergency contraception has the highest chances of working if taken within 24 hours of unprotected sex. It's possible for it to work up to five days after the incident, but the chances of it being effective after three days are very low.
Plan B contains a high dose of levonorgestrel, which is a hormone that's found in some birth control pills. This can keep pregnancy from occurring in a variety of ways. It may prevent an egg from leaving the ovaries, change the lining of the uterus to prevent implantation or stop sperm from reaching the egg. These things typically happen within a few days of unprotected sex if a woman is near the ovulation phase of her menstrual cycle.
Morning-after pills do not terminate pregnancies that have already occurred. After the sperm has fertilized the egg and the embryo has implanted in the uterus, these drugs are no longer effective. That's why you can still get pregnant even after taking Plan B. It's sometimes incorrectly referred to as the abortion pill. However, the abortion pill is actually another drug called Mifeprex that does terminate already-established pregnancies.
Plan B shouldn't be relied on as a regular form of birth control. It can be helpful in situations such as unplanned and unprotected sex, contraceptive failure or sexual assault. Examples of contraceptive failure include forgetting to take a birth control pill or having a condom break. After taking Plan B, you can't know whether you're pregnant until it's time for your next period. You should get a pregnancy test if you think that your period is late.