What happens if plan b works

The effectiveness of the morning-after pill can be hard to study, because it can be difficult to know if people are ovulating, when they had sex and what day they are on in their cycle 2,3. In the United States, the progestin-only emergency contraception pill can be purchased in pharmacies by anyone of any age without a prescription 1. You can take it for up to five days after intercourse. If you take it between three and five days, the rate of effectiveness is reduced 1.

It works by delaying the release of the egg from the ovary ovulation , preventing the sperm from fertilizing it 5.

Antiprogestin emergency contraception pills are the most effective form of emergency contraceptive pill 1 and available only by prescription.

This pill should be taken as soon as possible after unprotected sex 6 , but you can take it up to five days later 1. This emergency contraception pill changes the way progesterone works in your body 1. It works by preventing or slowing ovulation 1. When ovulation is postponed or halted, there is no egg for sperm to fertilize, and pregnancy is prevented. A person who takes emergency contraception can still get pregnant.

Here are the three primary reasons why this happens. Emergency birth control is all about timing. It's recommended that you take the pill as soon as you can—if you wait too long, you might miss the window during which the pill can be effective. If you have unprotected sex again after you take the pill in the same cycle, it could also fail 7. Healthcare providers use the Body Mass Index BMI scale to group people into generic categories based on height and weight 8.

Current studies show that emergency contraceptive pills are less effective for people who have a BMI of 30 or higher 7,9. Peak levels of Plan B in your bloodstream will occur about 1. Depending on where you are in your cycle, Plan B will likely delay ovulation for a few days, says Gariepy. And the levonorgestrel should leave your system after about a week or so, depending on how fast your metabolism is, Gariepy says.

However, it's important to note that plan B only works for the episode of unprotected sex you have already had. If you have unprotected sex shortly after taking plan B — like later that day or the following day — then you will need to take another dose of plan B to prevent pregnancy.

Plan B may cause side effects, which Gariepy says are most likely to occur within a few hours of taking the pill, since the peak levels in your blood will be around 1. Side effects will usually resolve within 24 hours and include :.

Be aware that there is a risk Plan B might not work for you if you fall into one of the following groups. Plan B is a type of emergency contraception that is very effective at preventing pregnancy if you take it within 24 hours of unprotected sex. The longer you wait to take it, the less effective it becomes.

More than occasional use more than once within a menstrual cycle or more than once a month may impact your menstrual cycle.

What to expect. These professionals have been trained to handle requests for emergency contraception sympathetically and confidentially.

In some cases, your pharmacist may refer you to a doctor or clinic for emergency contraception instead. Find a pharmacy. It can also be used more than once. Remember that it should never replace regular, long-term methods of contraception. It works by temporarily stopping the release of an egg from the ovary, preventing fertilization if ovulation has already occurred, or, if an egg has already been fertilized, preventing it from attaching to the wall of the uterus.

Learn more. Learn how to find free birth control without health insurance here. Skip to main content Search for a topic or drug. How effective is Plan B, and how long is it effective for? Top Reads in Drug Info. Can you mix Trintellix and alcohol? Does hydroxyzine for anxiety work? Do coffee and Zoloft mix?

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